Lokman Gunduz
email: lgunduz68@gmail.com

Ismail H Genc
email: igenc@aus.edu

Ahmet Faruk Aysan

Buying citizenship: A boon to district-level house prices in Istanbul

Keywords: Citizenship by investment program, house prices, immigration, Istanbul JEL codes: C21, J15, R38, R21

Citizenship by investment (CBI) programs have recently garnered significant academic and media attention. Turkey introduced such a program in 2017 that offers citizenship in exchange for investment in residential property. Eventually, thousands of foreigners, mainly from the Middle East and Asia have purchased houses, particularly in Istanbul.

Foreigners' share in total houses sold in Istanbul almost sextupled and exceeded 10 percent of total sales. This study estimates the short-run impact of relatively wealthy foreigners on the residential property prices in Istanbul to buy a Turkish passport. It finds that the Turkish CBI program positively impacts house prices by two percent in the districts, which are likely to be favored most by immigrant investors.

Introduction

There is a proliferation of investment-based migration programs in recent years [START_REF] Gamlen | Citizenship as sovereign wealth: Re-thinking investor immigration[END_REF][START_REF] Surak | Who wants to buy a visa? Comparing the uptake of residence by investment programs in the European Union[END_REF][START_REF] Dzankic | The Global Market for Investor Citizenship[END_REF]. Several countries across the globe try to attract investment by granting investors either residence or citizenship rights. These are featured in advertorials as "golden visa" and "golden passport" options. The former is a more common practice adopted by countries worldwide such as the USA, the UK, Canada, Belgium, Australia, Portugal, and Singapore.1 . The latter is relatively new and includes both discretionary acquisitions of citizenship on the grounds of national economic interest and detailed citizenship by investment (CBI) programs [START_REF] Dzankic | Immigrant investor programs in the European Union[END_REF][START_REF] Dzankic | The Global Market for Investor Citizenship[END_REF]. Economic difficulties after the European debt crisis have led several European countries to launch either economic residency programs as in Portugal, Spain, Greece, and Ireland or citizenship by investment (CBI) programs as in the case of Malta and Cyprus (See, among others, Parker, 2016;[START_REF] Ampudia De Haro | Buying citizenship? Chinese golden visa Migrants in Portugal[END_REF]Xu et.al. 2015).

This year marks the 37 th anniversary of CBI programs. In simple terms, they refer to a direct exchange between a financial disbursement in the form of capital investment or property purchase and citizenship status. Several islands in the Caribbean Sea, including St. Kitts and Nevis and the Commonwealth of Dominica, have long-running CBI programs. In Europe, for example, Austria has the practice of granting citizenship to investors since 1985, but its regulation is less detailed than in the Caribbean islands, and it is more reliant on the discretionary power of the state authority. More recently, several CBI schemes have been introduced in small Caribbean countries such as Antigua and Barbuda, Grenada, and St. Lucia and in relatively large emerging countries such as Turkey (see Table 1). According to the Citizenship by Investment index (https://cbiindex.com/reports/) published by The Financial Times' Professional Wealth Management (PWM) magazine, fourteen countries offer their passports for sale to the wealthy as of 2020. There is an increase in the number of countries offering CBI schemes together with a substantial increase in their applicants [START_REF] Dzankic | The Global Market for Investor Citizenship[END_REF].

The global market for CBI programs is estimated to be around USD 25bn a year (Treanor and Nunis, 2019).

[Table 1 near here]

The CBI programs have an economic rationale. Cross-border capital flows into host countries can be substantial for small countries. For example, St. Kitts and Nevis witnessed significant inflows to its public sector alone, reaching nearly 25 percent of GDP in 2013 [START_REF] Xu | Too much of a good thing? Prudent management of inflows under economic citizenship programs[END_REF].

In addition to such direct effects, these programs can also lead to positive spillover effects in some sectors depending on the design and magnitude of the program. Lately, CBI schemes are very popular with real estate options where investment in residential houses is offered to acquire citizenship. Foreign investment in real estate is expected to increase real estate prices. It is reported that it led to a boom in the construction sector in St. Kitts and Nevis in 2015 and boosted the price of luxury real estate in Portugal in 2012 [START_REF] Xu | Too much of a good thing? Prudent management of inflows under economic citizenship programs[END_REF]. Leaving aside the extant literature on the impact of migration on house prices, there is, however, a shortage of empirical studies directly examining the relationship between the CBI programs and real estate prices. As a latecomer to the CBI club, Turkey offers a unique environment to investigate the impact of CBI schemes on local house prices. Its program particularly encourages investment in the property market. It does not require any other contribution to the government in some form of a registration fee or any additional non-refundable contribution to any government fund.

Turkey launched its CBI program in January 2017. In due course, it has witnessed a dramatic increase in house sales to foreigners and received a lot of public attention through extensive media coverage. Therefore, we aim to investigate the impact of this program on the residential house prices in Istanbul, where more than half of total house sales to foreigners have materialized during that period. We compare local house price movements in the short window immediately preceding and following the implementation of the CBI program in January 2017.

We compare the effect of this program on the house prices in the districts of Istanbul with high immigrant concentration to the low immigrant concentration over the same period.

We base our assumption of destination choice of new immigrants on the concept of social networks according to which immigrants tend to live in districts with a large share of immigrants with a similar background or a shared ethnicity 2 . [START_REF] Card | Immigrant inflows, native outflows, and the local market impacts of higher immigration[END_REF] applied this assumption in the migration literature. It implies that the destination choice of current immigrants within the country is highly correlated with the number of compatriots already established in that specific destination (i.e., city, province, or region). We demonstrate that the 2 One may see some of the related works of the authors as follows in the references: Aysan destination choice of current immigrants in Istanbul due to the Turkish CBI program has eventually contributed to an upsurge in house prices in several districts where the share of foreign-born Istanbul residents (i.e., immigrants) is relatively high. That is, we show that local house prices rise disproportionally more in districts with a higher foreign population density (more than five percent) after the implementation of the CBI program. We find that it had a positive impact on the house prices by two percent in the districts which are likely to be favored most by immigrant investors.

Our paper contributes to the extensive literature on the economic effects of immigration in three specific ways. First, there is less work directed toward understanding the effects of relatively better-off immigrants on housing markets. It should be noted that Turkey is not one of the top destinations for high-net-worth individuals (HNWIs) from developing countries. Therefore, relatively better-off or wealthy immigrants mentioned in this paper do not correspond to HNWIs. They instead designate persons whose investible wealth exceeds 250K US dollars.

How wealthy foreigners (immigrants) affect local housing markets is an empirical question. It can directly increase the demand for housing, leading to an increase in local house prices.

However, the preferences of domestic residents can offset the direct effects of wealthy foreigners. If residents would like to avoid cultural diversity, then 'native outflows' can offset the upward price pressure. Empirical evidence concerning the overall relationship between immigration and property prices is so far mixed. Some studies predict that immigration increases house prices because of an increase in demand for accommodation [START_REF] Gonzalez | Immigration and housing booms: evidence from Spain[END_REF][START_REF] Saiz | Room in the kitchen for the melting pot: Immigration and rental prices[END_REF]2007), while some others argue the opposite due to a decline in perceived desirability of new neighbors [START_REF] Sa | Immigration and house prices in the UK[END_REF] or differences in housing tenure and usage of housing space between natives and immigrants [START_REF] Braakmann | Immigration and the property market: Evidence from England and Wales[END_REF]. In a comprehensive meta-regression analysis, [START_REF] Larkin | Do house prices ride the wave of immigration?[END_REF] find that immigration leads to an increase in house prices on average, but that effect is more limited in countries where locals are less hospitable to immigrants.

Our study is partly related to this strand of the literature but focuses on the impact of the CBI program on residential property prices per se. To the best of our knowledge, this is the first empirical paper examining the short-run impact of the CBI programs on the housing market.

Second, most of the existing literature understandably focuses on the advanced countries as cited above due to the massive influx of immigrants. In emerging countries, there are arguably only a few papers studying the role of immigration on housing markets despite the increase in human and capital mobility [START_REF] Kim | Foreign housing investment in Seoul: Origin of investors and location of investment[END_REF][START_REF] Kim | Ethnic connections, foreign housing investment and locality: a case study of Seoul[END_REF]). In the case of Turkey, studies are investigating the impact of refugees, but not that of immigrants or foreigners. For example, [START_REF] Balkan | Immigration, housing rents, and residential segregation: Evidence from Syrian refugees in Turkey[END_REF] and [START_REF] Tumen | The economic impact of Syrian refugees on host countries: Quasiexperimental evidence from Turkey[END_REF] show that Syrian refugee inflows have generated an increase in the rents of higher-quality housing units in the neighboring cities in the southeastern part of Turkey. They argue that these lend support to the residential segregation story in the Turkish case. Our paper is undoubtedly different from them regarding motivation, driving force, location, and unit of analysis. Finally, our work contributes to the burgeoning literature on the determinants of real estate prices in Turkey. Most of the previous studies such as Yener et.al. (2020) and [START_REF] Tunc | The Effect of credit supply on house prices: Evidence from Turkey[END_REF] employ house price data at the countrywide level or province-level at best and emphasize the role of macroeconomic indicators such as capital inflows, interest rates, and disposable income or some regional dynamics such as population density, unemployment, climate, and education. Our study utilizes the district-level data, points to the role of the Turkish CBI program and the inflow of relatively wealthy foreigners as another determinant of house prices, at least in some specific districts of Istanbul. Last but not least, from a political economy perspective, the current CBI program can be considered not merely as another example of the commodification of citizenship but more of an extension of the financialization of housing where the state itself effectively continues to expand the scale and scope of the housing-finance nexus. 3 The design of the Turkish CBI program lends support to the understanding that the Turkish government places the utmost importance on the development of the construction industry and takes an active role to back it in times of economic slowdown.

The paper is organized as follows. The next section gives the context of Istanbul and citizenship by investment program. Then, methodology and data are explained in the following two sections. In section 5, empirical results are presented and discussed with implications. Finally, the last section concludes.

The context of Istanbul and citizenship by investment program

For a long time, Turks have considered Istanbul a city where its land and stone are made of gold. Decades-long internal migration has played a role in establishing this convention among the inhabitants. Only in 2016, the number of out-migrants exceeded those of in-migrants in Istanbul, but the trend reversed in 2019 partly due to a rise in its foreign-born residents. 4

3 See Erguven (2020) and [START_REF] Yesilbag | The State-Orchestrated Financialization of Housing in Turkey[END_REF] for an extensive analysis of the financialization of housing in Turkey and [START_REF] Serin | The role of the state in the commodification of urban space: The case of branded housing projects, Istanbul[END_REF] for the role of the state acting as a regulatory mechanism, a land developer, and a house builder in the commodification of urban space in Istanbul. Also, see [START_REF] Mavelli | Citizenship for sale and the neoliberal political economy of belonging[END_REF] for a discussion of the relationship between citizenship by investment and neoliberal political economy. 4 According to an address-based registration system published by the Turkish Statistical Institute, the number of abroad-born residents in Istanbul has quadrupled in 2019 up from 4,166 in 2017. Its share as a percent of the Property investment in Istanbul has received increasing attention from foreign investors lately.

The year 2019 was a record year in terms of total houses sold to foreigners in Turkey and Istanbul when house sale figures reached 45,483 and 20,857 respectively, up from 18,189 sales and 5,811 sales in 2016. More importantly, foreigners were responsible for almost 10 out of 100 house sales in Istanbul in 2019, which was 3 out of 100 houses in 2016 and 2017 (Figure 1) The strong growth in property sales to foreign buyers in recent years was not only due to robust tourism but more due to the introduction of the CBI program

[Figure 1 near here]

The Turkish property market has been open to foreign buyers since 2002 [START_REF] Polat | Legal, economic, geographical and demographic analysis of the acquisition of real estate by foreigners in Turkey[END_REF].

However, only nationals of countries like Britain and Germany that allow Turkish citizens reciprocal rights were allowed to purchase properties in a few zones. These zones were abolished in 2005, and the reciprocity condition ended in 2012.5 Since then, thousands of foreigners from Russia to GCC countries, which were previously banned, have successfully acquired properties in Turkey, most notably in Istanbul, in the Mediterranean resort city of Antalya, and the industrial city of Bursa. Foreigners could now buy up to 30 hectares of property (up from 2.5 hectares) without special permission. On the other hand, a significant policy change occurred when Turkey introduced its CBI scheme in January 2017 after July 15, 2016 coup attempt, which sent a shockwave throughout the economy. Among the several options in the scheme, purchasing property was particularly attractive to get a Turkish passport, which required a minimum amount of USD 1 million investment. This amount was reduced due to financial woes starting in August 2018. New regulations were introduced in September 2018 and granted citizenship to foreigners in exchange for i) purchasing real estate worth at least US$ 250,000, down from US$ 1 million; ii) or putting US$ 500,000 into a fixed capital investment;

iii) or keeping at least US$ 500,000 in a Turkish bank account for a minimum of three years, down from the earlier cap of US$ 3 million; increase in in-migration was 15.2 percent, which implies a significant contribution. The number of abroad-born residents in Istanbul has reached 16, 653 people in 2019 up from 4,166 in 2017. It represents almost 14 percent of net migration and 3.4 percent of net migration and in-migration of Istanbul respectively in 2019. The share of abroad-born residents in Istanbul was less than 1 percent of total in-migration in 2017. iv) or generating 50 jobs, down from 100 jobs. 6

This scheme was widely seen as a bid to stimulate the slumping real estate market. It arrived after the Turkish Lira had already plummeted more than forty percent against the US dollar in August 2018 and economic activity in the real estate and construction industry continued to decline. 7 Later in December 2018, the Turkish government put another amendment that allows foreigners to apply for Turkish citizenship by purchasing real estates from unfinished or offplan projects. 8 These rules have led to a real estate route in Turkey as one of the low-cost CBI programs, of which the immediate impact on the housing market was widely covered and commented on by the press. 9 According to the Turkish Statistical Institute, the number of houses sold to foreigners more than doubled, reaching 4,200 homes per month after September 2018.

It reached an all-time high with 6,327 monthly sales in October 2018. The number of houses sold was about 41,151 units between January 2017 and August 2018, while it reached 67,288 homes between September 2018 and December 2019. Most of the foreign buyers are Turkey's neighboring countries. Iraqis, Iranians, and Saudis were the biggest buyers of Turkish property.

According to 2019 cumulative statistics, Arab countries, including Iraq, Saudi Arabia, Kuwait, Jordan, Yemen, Palestine, Libya, Egypt, Qatar, and Lebanon, constitute 42 percent of total foreign buyers. Iranians follow them with a 12 percent share. Nationals of advanced countries, including Germany, the UK, Sweden, and the US, have 10 percent. The rest of the countries are Russia (5 percent), Afghanistan (5 percent), and Azerbaijan (3 percent).

There is limited information regarding the overall number and breakdown of foreigners acquiring citizenship due to their investment in Turkey. Ministry of Internal Affairs stated that overall more than 9000 foreign investors have benefited from the Turkish CBI program and invested in around USD 2.8 billion within three years, and the overwhelming majority of the investment has been realized in 2019. 10 Accordingly, Iranians occupy the top spot and have a share of 26 percent in the total number of citizenships granted. Nationals of Arab countriesthose of Iraq, Yemen, Palestine, Jordan, Libya, and Egypt -represent 48 percent of the total citizenships granted. Other significant countries are Afghanistan, with a share of 15 percent, China, with a share of 8 percent, and Pakistan (3 percent). 11 Anecdotal evidence from the field, written press, and social media also suggest that Iranians, Arab nationals, and Afghan people are interested in investing in the Istanbul property market and receiving citizenship in due course. 12 Relatively wealthy nationals of Iraq, Iran, Yemen, Libya, and Afghanistan reasonably would prefer to invest in the property market to get a Turkish passport. These countries suffer a lot from recent political and economic uncertainties in their homelands. Correspondingly, [START_REF] Badarinza | Home away from home? Foreign demand and London house prices[END_REF] emphasize the role of foreigners facing political risk in their home countries and foreign demand as an important determinant of London house prices. Indeed, several foreign investors designate Turkey as a haven, an open society, and a more Europeanized country. Besides, a Turkish passport allows them to travel more freely across the globe with more visa-free travel options than their home countries' passports [START_REF] Wither | Iranian home buyers dodge sanctions, make Turkey their plan B[END_REF].

2.1.Migrant networks and segregation in Istanbul

Turkey has been experiencing an influx of foreigners for a long time as a country of transit to the European Union for irregular migrants and a country of refugees for asylum seekers. More recently, it has also become a country of immigration as a result of intense migratory movements over the last three decades (among others, see [START_REF] İçduygu | Land of Diverse Migrations: Challenges of Emigration and Immigration in Turkey[END_REF][START_REF] Kirişci | Turkey: A Country of transition from emigration to immigration[END_REF]. In particular, Istanbul has become a top destination for movers from the Middle East, Africa, and Asia through migrant networks. Migrant networks are sets of interpersonal ties connecting movers, former movers, and non-movers in countries of origin and Istanbul through social connections, which are primarily based on kinship and friendship.

10 https://www.aa.com.tr/tr/ekonomi/yabanci-yatirimcidan-2-milyar-771-milyon-250-bin-dolarlik-katki/1748243 retrieved as of November 30, 2020. From a comparative perspective, Turkey's figures seem satisfactory, as well. For example, Portugal conceded 6,687 golden visas between 2012 and 2018 (Gaspar and de Haro, 2019). Malta has received 1742 applications since the inception of the individual investor program as of 30 June 2019. Available at https://oriip.gov.mt/en/Documents/Reports/Annual%20Report%202019.pdf. [Accessed 30 November 2020]. See also [START_REF] Surak | Who wants to buy a visa? Comparing the uptake of residence by investment programs in the European Union[END_REF] to compare the number of applications with the EU member countries. 11 (http://www.yourkeyturkey.gov.tr/citizen ship-statistics).

12 One can also examine Google Trends to get an understanding of how the Turkish CBI program has become popular over time. It shows that there is a worldwide increase in the search interest for the terms "Citizenship by Investment Turkey" or "Turkey passport" after the policy change in September 2018. Investors from the Arab countries, Iran, and Pakistan have shown greater interest after the policy change which was probably materialized later in official house sale statistics (see Google Trends).

After continuous waves of immigration to Istanbul starting from the 1980s, it is very likely to observe a "cumulative causation" whereby multiple ties to communities or origin facilitate ongoing and at times increasing migration [START_REF] Massey | Theories of international migration: A review and appraisal[END_REF][START_REF] Massey | Immigrants and the American City[END_REF]Wilson, 1994).

For instance, [START_REF] İçduygu | Afghan migration through Turkey to Europe: Seeking refuge, forming diaspora, and becoming citizens[END_REF] and [START_REF] Kaya | Istanbul as a space of cultural affinity for Syrian refugees[END_REF] show how new migrants and refugees join the old settlers in particular locations and tend to live in Istanbul, primarily by coming through their networks of relatives and friends. As observed in several countries, foreigners, particularly those with the same community, ethnicity, and culture, prefer to live together in the same neighborhood or district. Indeed, some of the districts of Istanbul are associated with the spatial concentration of particular migrant networks. Some of the prominent ones are the Syrian community in Zeytinburnu, Küçükçekmece, Fatih, Bağcılar and Sultanbeyli districts, Iraqi community in Fatih and Esenyurt districts, Afghan community in Zeytinburnu and Beykoz districts, Chinese nationals from Xinjiang Uygur Autonomous Region of China in Zeytinburnu, Kucukcekmece and Silivri districts, and Syrian Turkmens in Esenler district. 13 Subsequently, an obvious outcome of such a spatial concentration is the segregation from the broader local population, which refers to the segregated geographies of neighborhoods or districts reflecting a history of immigration, internal migration, class, and intergroup ethnic and racial relations, and conflict [START_REF] Newbold | Commercializing citizenship in crisis EU: The case of immigrant investor programmes[END_REF]. Parallel to the findings of the related literature, Istanbul broadly seems to display two different patterns of residential segregation [START_REF] Zelinsky | Heterolocalism: an alternative model of the socio-spatial behaviour of immigrant ethnic communities[END_REF][START_REF] Allen | Spatial Patterns of Immigrant Assimilation[END_REF][START_REF] Price | Edge gateways: immigrants, suburbs, and the politics of reception in metropolitan Washington[END_REF][START_REF] İçduygu | Syrian refugees in Turkey: Insecure lives in an environment of pseudo-integration[END_REF]. On the one hand, most immigrants continue to settle in traditional and segregated enclaves in the inner city that offer less expensive housing, public transportation, and access to employment, such as Fatih and Zeytinburnu districts. On the other hand, new arrival groups bypass traditional innercity enclaves to settle in more dispersed and new suburban areas such as Basaksehir and Esenyurt, reflecting different housing opportunities. In the latter case, more often, both poor and wealthier immigrants coexist in the same district, albeit in separate quarters reflecting their distinct level of economic characteristics. As most of them belong to the same ethnicity (i.e., Arab), it is easier to make friendship with co-ethnics. As known very well, immigrants are more likely to have strong ties to co-ethnics and family members in the host country [START_REF] Fietz | Counting on kin: The satisfaction of migrants with their social networks in Germany[END_REF][START_REF] Viruell-Fuentes | Contextualizing nativity status, Latino social ties, and ethnic enclaves: an examination of the 'immigrant social ties hypothesis[END_REF]. Moreover, immigrants can talk to each other in their mother tongue and maintain familiar habits in a different culture, which keep them wellgrounded [START_REF] Jasinskaja-Lahti | Perceived discrimination, social support networks, and psychological well-being among three immigrant groups[END_REF]. In fact, in Istanbul, a common language seems to be more relevant than the common country in determining the geographical boundary of immigrant 13 The United Nations Migration Agency situation and migration reports. Available at https://migration.iom.int enclaves. It is an essential factor that separates immigrants from Turkish citizens, as well [START_REF] Kaya | Istanbul as a space of cultural affinity for Syrian refugees[END_REF]). 14

Methodology

We employ the difference-in-differences (DiD) approach to identify house price variation in the districts of Istanbul before and after the implementation of the CBI program, which we treat as an exogenous shock. In a similar fashion to [START_REF] Badarinza | Home away from home? Foreign demand and London house prices[END_REF], we conjecture that districts of Istanbul with relatively high pre-existing shares of foreign-born residents are preferred habitats for foreign property purchases. Moreover, [START_REF] Bailey | Social connectedness in urban areas[END_REF] show that social connectedness is a strong predictor for migration. Theoretically, homophily is known to be an important explanatory factor for the configuration of personal networks [START_REF] Mcpherson | Birds of a feather: Homophily in social networks[END_REF]. For example, leaving aside numerous cases in developed countries, [START_REF] Kim | Foreign housing investment in Seoul: Origin of investors and location of investment[END_REF] show that the location of foreign-owned houses is linked to the geography of ethnic clusters in Seoul, Korea. The assumption that new immigrants tend to locate in areas with a large share of immigrants of the same origin or ethnicity is well known in the literature and mentioned above.

If this conjecture were right, we would expect to see relatively higher house prices in these specific districts of Istanbul than other districts after the implementation of the CBI program.

Accordingly, we define our control group as the districts where the proportion of the foreign population (i.e., immigrants) is low, and our treatment group as the districts where the proportion of the foreign population is relatively higher. In other words, our empirical strategy relies on comparing house prices that are subject to larger compatriot inflows with those that are not, before and after January 2017. More specifically, the pre-treatment period includes the period between 2014m1 and 2016m12, while the post-treatment period spans from 2017m1 to 2019m11. We ignore the recent dates due to the impact of the Covid-19 pandemic. [START_REF] Tumen | The economic impact of Syrian refugees on host countries: Quasiexperimental evidence from Turkey[END_REF]Altindag et.al. (2020) have also adopted DiD approach in their analysis of the economic impact of Syrian refugees in Turkey.

To segregate the so-called immigrant and non-immigrant districts, in the relative sense, we sort the districts in terms of the share of the foreign population in the district population. Then, we assume that the first five districts with the highest foreign ratio make up a group. Afterward, we run a mean equality test between this group and the next district with the next share of the foreign population. If the mean does not statistically differ from this group, we add it to the 14 There is certainly room for development and future research to better understand the nature of wealthy immigrants in Istanbul within the context of social/ethnic networks both at the conceptual and empirical level. Particularly an empirical study can contribute to a better understanding of motives for Turkish citizenship by investment program. We leave this issue for future work.

group and proceed to test the next group. We stop when we find a district with a statistically significantly different (smaller) share of the immigrant population. While the former constitutes our treatment, the latter becomes the control group of districts.

Given the short period, we also conjecture that the supply of housing is inelastic. The existing literature essentially confirms the expectation that the supply curve is inelastic in the short-run and elastic in the long-run [START_REF] Harter-Dreiman | Drawing inferences about housing supply elasticity from house price responses to income shocks[END_REF]. In other words, even in the case of an increase in demand for housing, the supply of housing will not immediately respond, as the construction of new houses will take time. More importantly, in an environment where the housing market is already struggling, entrepreneurs will not be eager to build more homes. As it takes time to build new houses, the housing supply is constant in the short run. Turkish Statistical Institute does not publish construction permits at the district level but Istanbul's aggregate data shows that average construction permits are even lower in the post-policy period, most likely due to worsening economic conditions.

Finally, we estimate the following difference-in-differences model

ln#ℎ% !,#,$ & = ( % + ( & *+* + , ! + , # + , $ + -+ . !,#,$
where ℎ% represents real house prices in a certain district indexed by r. The year and month are indexed by / and 1, respectively. The program's impact on house prices is given by variable *+*, which is defined as the multiplication of a dummy variable, which takes on a value of one for the post-treatment period, and another dummy for districts, which are classified as the treatment districts. , ' where 2 = 3, /, 1 are the fixed effects for the district, year, and month. In our models, we try both 'combined' time effects where year and month are assumed one period as well as 'decoupled' time effects. We estimate all models with clustering standard errors.represents a set of other macroeconomic explanatory variables such as the real mortgage interest rates and real effective exchange rate of the Turkish Lira. These variables are common to all regions. Another variable that could potentially enteris inflation. However, since all of our independent and dependent variables are real, i.e., already adjusted for inflation, we do not include it among the covariates. Ifis not included among the explanatory variables, we have a simple DiD model. This is reported in the paper. Although not reported in the paper, we also estimate a random effect model when feasible for comparison purposes.

Data

Our dataset includes house prices at the district level in Istanbul and covers the period between 2014m1 and 2019m11, which we obtained from the Central Bank of the Republic of Turkey (CBRT). As the ownership details of the properties are mostly opaque and local registry data are not circulated, we are condemned to rely on time series data. Istanbul has 39 districts, out of which only 34 districts have house price data. The banks in Turkey extend individual housing loans based on the valuation reports prepared by real estate appraisal companies. The CBRT compiles the price data from these valuation reports at the time of approval of housing loans.

The actual sale or utilization of the housing loan is not required, but all appraised residential properties are included in the scope of the data. These prices are then used as a proxy for each district's house prices after adjusted for quality changes related to housing characteristics. Our data are the monthly median price (in Turkish Lira) per square meter of these residential properties. 15 We generate real mortgage interest rates by subtracting CPI inflation for Istanbul from the nominal mortgage interest rates. The CPI-based real effective exchange rates are directly obtained from the Central Bank (CBRT). All data are monthly for the period of 2014m1 and 2019m11.

There are two sources of information concerning the share of the foreign population in the districts to identify treatment and control groups. Turkish Statistical Institute publishes foreignborn population annually starting from 2014 at the district level based on the addressbased census. It does not provide the nationality of those classified as foreign-born. Syrian refugees are normally not included in that registry because they are under temporary protection.

We suspect that Syrian refugees make up for the majority of foreign-born residents who migrated to Istanbul after 2014.

The United Nations Migration Agency (International Organization for Migration -IOM) also publishes analysis reports based on the fieldwork in which the actual number of nationalities of the foreign population is provided at the district level in Istanbul. Therefore, there is a discrepancy in the number of the foreign population between the official and the fieldwork The figures with the refugees and those without, however, correlate with each other closely. In other words, the foreigners (migrants and immigrants) and Syrian refugees seem to prefer living in the same districts, most likely due to sharing the same ethnicity, language, or other sociocultural characteristics as mentioned above. 17 United Nations reports reveal that foreigners are primarily from Arab countries, Iran, Afghanistan, Turkmenistan, Uzbekistan, China, Pakistan, Azerbaijan, and Russian Federation. Consequently, we rely on the actual data from the fieldwork study in 2017 to utilize the share of the foreign population in each district.

Irrespective of whether or not we include Syrian refugees in foreign population figures, members of the treatment and control groups do not change substantially.

[Figure 2 near here] Figure 2 presents a visual display of our treatment and control groups based on the ratio of all foreigners to the local population in each district. Our treatment group consists of 17 districts, which are the districts with foreigners' concentration of more than 5 percent. These districts are Arnavutkoy, Avcılar, Bagcılar, Bahcelievler, Basaksehir, Bayrampasa, Beyoglu, Esenler, Esenyurt, Eyup, Fatih, Gaziosmanpasa, Gungoren, Kagithane, Kucukcekmece, Sultangazi, and Zeytinburnu. The control group of districts has a much lower ratio of foreigners to population, mostly less than two to three percent in many cases.

Results and Discussions

As outlined above, we treat the introduction of the CBI program in January 2017 as an exogenous shock and expect an increase in house prices due to a rise in the arrival of wealthy foreigners. As in [START_REF] Bertoli | Integration of Syrian refugees: Insights from D4R, media events and housing market data[END_REF], we reason that the foreigners who would like to become Turkish citizens choose the destination with relatively a higher foreign population density of which most have similar origin or ethnicity. We present our results in Table 2. Model 1 in 16 This is expected as there are too many unregistered foreigners. IOM's statistics depend on the information collected from local authorities in each neighborhood (namely from Mukhtars) and are expected to be accurate and timely. 17 Syrian refugees in Turkey are not a party to the Turkish CBI program. The majority of the Syrian refugees are poor. However, they have an influential social network in the Arab world. Part of those residing in Istanbul is relatively well-educated and successful entrepreneurs. This is perhaps one of the reasons why the Turkish government has granted citizenship to over 90,000 Syrian refugees, most of whom live in Istanbul. Available at https://tr.euronews.com/2019/08/02/bakan-soylu-92-bin-suriyeliye-vatandaslik-verildi-suleyman-soylu and https://www.bbc.com/turkce/haberler-turkiye-49150143.

Column 1 in the table displays a simple DiD model without any covariates, whereas the two other models in Columns 2 and 3 present DiD models with covariates. In addition, all models employ clustered standard errors. As a precursor to the DiD estimation, we test the so-called parallel trend assumption and find the coefficient on an interaction term between a time trend and DiD coefficient insignificant. 18 The Adjusted R2 from the simple DiD model (Column 1) and the DiD model with covariates and decoupled time effects (Column 3) have about 98 percent explanatory power. However, the DiD model with covariates and combined time effects (Column 2) has a meager one percent explanatory power. Overall, our results from Table 2 show that the coefficient on DiD, which is the differences in house price across the treatment and control group, is statistically significant under different setups. In other words, the house prices in the treatment districts rise more than house prices in the control districts after the CBI program. The magnitude of this increase is about two percent, irrespective of the model specification.

Foreigners' share in total houses sold in Istanbul almost sextupled and exceeded 12 percent of total sales after introducing the CBI program. Assuming that most foreigners would have purchased homes in the treatment districts, its volume looks high. Besides, an increase in the number of Syrian refugees in the treatment districts would likely cause higher rent prices, hence house prices. Moreover, anecdotal evidence from the field shows that particular foreign investors avoid registering their ownership. Instead, they ask their naturalized Turkish relatives/friends to have ownership of the property. For instance, these people are said to be Chinese nationals from the Xinjiang Uygur Autonomous Region of China, and they keep their identity secret due to security reasons. These issues are hard to incorporate into the model, but they imply unregistered or unrecorded purchases by foreigners. Finally, a two percent difference in house prices seems a reasonable estimate and similar to those in some other countries. For instance, using a DiD approach, Pavlov and Sommerville (2020) recently found that unexpected suspension of the investor immigration program in Canada negatively impacted house prices of 1.7-2.6% in the neighborhoods and market segments favored by the investor immigrants.

Additionally, as obtained via Models 2 and 3, the real effective exchange rate coefficient is positive but only significant in Model 3. This suggests that an increase in the foreign exchange rate, which is the depreciation of the Turkish currency, would indirectly make a particular house 18 See [START_REF] Cerulli | Estimation of pre-and posttreatment average treatment effects with binary time-varying treatment using Stata[END_REF] for testing the parallel-trend assumption.

cheaper, especially for foreigners. That would increase demand for houses, thus, increase house prices, ceteris paribus. However, the impact of the real effective exchange rate on real house prices is negligible. Numerically speaking, for every one-unit increase in the value of the foreign exchange, the house prices increase by about 0.31%. Although the negative coefficient on the real mortgage interest rates in Models 2 and 3 would be as expected, it is statistically insignificant in both models.

[Table 2. near here]

Our findings align with those of [START_REF] Gonzalez | Immigration and housing booms: evidence from Spain[END_REF]; [START_REF] Saiz | Room in the kitchen for the melting pot: Immigration and rental prices[END_REF]2007); [START_REF] Degen | Immigration and Swiss house prices[END_REF][START_REF] Larkin | Do house prices ride the wave of immigration?[END_REF], as opposed to [START_REF] Sa | Immigration and house prices in the UK[END_REF] and [START_REF] Braakmann | Immigration and the property market: Evidence from England and Wales[END_REF] where the former group of authors also find a rise in house prices because of an increase in the immigration inflow. The likely counter impact of domestic residents' preferences to avoid living in the same districts, if they exist in the context of Istanbul, do not offset the aforementioned positive impact. It should be noted that average house prices in the control districts are higher than that of treatment districts in pre and after the CBI program. However, there is undoubtedly a need to investigate this issue further at the neighborhood level when microdata is available. The district-level data cannot easily reveal residents' preferences. For example, in a different context using micro-level data, [START_REF] Balkan | Immigration, housing rents, and residential segregation: Evidence from Syrian refugees in Turkey[END_REF] find that the massive influx of Syrian refugees in the southeastern part of Turkey has led to increased rents of higher quality housing units in the regions where residents live. Alternatively, wealthy foreigners appear to attenuate the adverse effects of immigrant volumes on house price levels. Their effects are similar to those resulting from foreign direct investment in residential real estate.

Consequently, a sudden increase in foreigners' influx initiates a positive housing demand shock, especially in the districts of Istanbul with a higher density of foreign population. This is in line with the recent literature such as [START_REF] Kim | Foreign housing investment in Seoul: Origin of investors and location of investment[END_REF] and [START_REF] Jun | Spatial concentrations of Korean-Chinese and determinants of their residential location choice in Seoul[END_REF], which shows how the location of foreign-owned houses is linked to the geography of ethnic clusters in the case of Seoul, Korea.

Inevitably, one should need to take a degree of caution in interpreting overall results. First, what percentage of the foreign population constitutes a treatment district is an important issue. For this purpose, we also employed median as another cut-off level for foreign population concentration to determine the treatment districts. Additionally, we examined the sensitivity of results when we changed the reference year to 2014 and used the official data for the foreign-born population, a year before the influx of Syrian refugees to Istanbul. To a large degree, the results are supportive of the significant impact of the CBI program on residential property prices. One can further argue that the policy change in the Turkish CBI program seems to contribute to some relaxation in the official treatment against foreigners. This is why Istanbul now hosts thousands of unregistered migrants, and their increasing numbers contribute to housing demand. Secondly, due to privacy and lack of micro-level data, it is challenging to identify the houses that foreign investors have purchased to acquire citizenship and compare their prices before and after the CBI program. It is, however, not unique to this study. In addition to the cautious and credible determination of treatment districts, wealthy foreigners mostly from Arab countries and Iran prefer to live in relatively high-quality apartments but with a shared culture and similar ethnicity in the same districts or neighborhoods lend support to our approach. Moreover, it should also be kept in mind that foreigners might not purchase real estate only for the sake of acquiring a Turkish passport. Foreigners from the Gulf countries and developed countries seem to belong to this group of investors.

Besides, Syrian refugees in Turkey are relatively poor. There seem to be two issues regarding Syrians in Istanbul. Most Syrian residents in Istanbul are from Aleppo, and Aleppo's entrepreneurs are known to have had strong social and commercial networks with their counterparts in Istanbul and Iraq dating back to the period of the Ottoman Empire. Put it simply, not all Syrians in Istanbul are poor, and at least a small part of them run their businesses successfully. In addition, those relatively wealthier and well-educated have already acquired Turkish citizenship. As a result, some Syrian refugees have easily settled in the districts where wealthy foreigners such as those from Iraq also live. Secondly, a common language seems to be more relevant than the same country or similar socio-economic background in determining the geographical boundaries of immigrant enclaves. That is one of the reasons why poor Syrians can settle in the same districts but in separate neighborhoods known to have bad housing conditions. As in other big metropolises, one can observe a good neighborhood near a worse one, both in the same district in Istanbul. The UN statistics from the field support our contention (please see, the United Nations Migration Agency situation and migration report. Available at https://migration.iom.int).

Conclusion

Citizenship by investment programs has recently garnered significant academic and media attention. Turkey introduced such a program in 2017 that offers citizenship in exchange for investment in residential property. Its program has become relatively cheap and encouraged foreigners to apply for Turkish citizenship by purchasing real estate. Eventually, thousands of foreigners, particularly from the Middle East and Asia have bought houses in Istanbul.

Foreigners' share in total houses sold in Istanbul almost sextupled and exceeded 10 percent of total sales.

In this paper, we show that the influx of foreigners after the introduction of the CBI program has eventually contributed to an upsurge in house prices of the districts of Istanbul in which the share of foreigners is relatively high. More specifically, local house prices rise disproportionally more in districts with a higher foreign population density (more than five percent) after the Turkish CBI program started. It has a positive impact on the house prices by two percent in the districts, which are likely to be favored most by investor immigrants. This finding is in contrast to previous results on immigration and real estate prices. It suggests that if immigrants are many and relatively better off, they can raise the house prices in the districts they choose to settle.

Our study has two broad policy implications. First, countries can attract more immigrants if they decrease the cost of immigrant investor programs -and vice versa. Second, if the CBI program mainly works through the real estate route, as in the case of Turkey, it can lead to changes in the house prices in particular locations. In that case, the economic benefits of the CBI may not accrue to the whole country or economy but some specific areas or sectors of the economy. One alternative would be to modify the design of the CBI programs so that it can help spread the inflows to other economic sectors and locations without generating excessive pressures in the construction and real estate sectors.

We acknowledge some limitations to this study. We were able to obtain data on house prices at the district level, but not at the individual house level or the foreign investor level. It is very challenging to get both monthly and local data, particularly in emerging markets. As such, our model essentially includes macro variables. There are undoubtedly several local demand/supply variables, including location-specific factors, that drive house prices. They vary from the local market conditions in a particular location to the quality of life and the amount of housing stock in that specific location. However, given the span of data, wild swings in the behavior of the market participants would be highly unlikely based on these variables. Furthermore, considering the worsening economic climate in Turkey at the time of the CBI program, we do not think that local demand/supply variables would respond quickly and differently to reduce the program's impact on house prices.

On the other hand, Turkey certainly needs a high level of transparency regarding its CBI program. Nonetheless, we hope to spark a much-needed research agenda around the CBI programs and their impact on real estate prices or investment. Additional empirical studies can enhance both the debates about these programs and our understanding of their consequences. to 1% and 5% significance levels respectively. The dependent variable is the natural log of real house prices. !"! is the multiplication of two dummy variables representing the treatment districts and the post-treatment period. Clustering standard errors are in the parentheses. The number of observations in the pre-treatment period is 680 while it is 544 in the post-treatment. All models are fixed effect estimations.

  2021, Aysan & Disli & Ozturk 2014, Aysan & Disli & Nagayev & Rizkiah & Salim 2021, Aysan & Ertek & Ozturk 2008, Aysan & Güler & Orman 2013a and Aysan & Nabli & Véganzonéz-Varoudakis 2008.

FigureFigure 2 .

 2 Figure 1. Foreigners' share in house sales in Istanbul and Turkey

6

  See the Presidential Decree No. 106 published in the Official Gazette dated September 19, 2018 7 By the end of the last quarter of 2018, the Turkish economy went into recession. See also real estate sector reports in Turkey available at https://www.gyoder.org.tr/uploads/gyoder_gosterge/GOSTERGE-CEYREK1-2019-ING-_1_.pdf [Accessed 30 September 2020].8 See the Presidential Decree No. 418 in the Official Gazette dated December 7, 2018 9 See, for example, "Turkish passport demand soars as rules relaxed", The Financial Times, Jan 27, 2019; Foreign Buyers Flood Turkey's Struggling Housing Market, Mansion Global, January 2019; Turkish property sales to foreigners keep up with strong performance, post all-time high in 5 months of 2019, Daily Sabah,Jun 17, 2019; "Property sales to foreigners hit record levels in Turkey", TRTWorld, Apr 18, 2019; Passport demand soars after Turkey slashes cost, Ahval News, Jan 28, 2019."Iranian home buyers dodge sanctions, make Turkey their plan B, Reuters, October 1, 2019, available at https://www.reuters.com/article/us-turkey-iranians-idUSKBN1WG3ON; "Saudis snap up homes in Turkey as top foreign buyers", The Times, 29 August 2019; "House Hunting in … Turkey" The New York Times, 9 Jan 2019.

  /www.tcmb.gov.tr/wps/wcm/connect/EN/TCMB+EN/Main+Menu/Statistics/Real+Sector+Statistics/Resi dential+Property+Price+Index/ statistics because the fieldwork data include Syrian refugees and other unregistered foreigners. 16

	15	Please	see	for	more	detail:
	https:/

Table 2 . Estimation results of difference-in-differences model of real house prices

 2

	Variables	Model 1	Model 2	Model 3
	Constant	2.423 (2211.866)***	2.337 (15.272)***	2.010 (18.980)***
	DiD	0.0202 (5.232)***	0.0207 (5.495)***	0.0202 (5.292)***
	Real effective exchange rate		0.0015 (1.165)	0.0031 (3.061)***
	Real mortgage interest rate		-0.3431 (-1.352)	-0.164 (-1.014)
	Region fixed effects	yes	yes	yes
	Combined time fixed effects	yes	yes
	Decoupled time fixed effects			yes
	Adjusted R2	0.9821	0.0125
	Numbers of observations	2343	2343	2343
	Note: *** and **refer

By

2017, nearly half of the European Union member states host golden visa programs[START_REF] Surak | Who wants to buy a visa? Comparing the uptake of residence by investment programs in the European Union[END_REF].

Under article 35 of the Land Registry Law No. 2644, amended by Law No.

6302, Turkey allowed citizens of 183 states to purchase real estate property in Turkey without being subject to any reciprocity principles as of May 18, 2012.

 Kitts and Nevis (1984)A minimum investment of USD 200,000 in a pre-approved property to be held for at least 7 years (or USD 400,000 resalable after 5 years). Minimum USD 400,000 investment in a preapproved project to be held for five years.

or a minimum investment of USD 1.5 million or in a joint investment totaling USD 5 million (each investor at least USD 400,000).

One-off, non-refundable donation of USD 100,000 to National Development Fund (further fees for additional dependents) Grenada (2014) Minimum USD 350,000 investment in a preapproved property project to be held for at least 5 years N/A A donation of USD 150,000 to the National Transformation Fund (further fees for spouse and additional dependents) Malta ( 2014)

Purchase a property for a minimum value of EUR 350,000 (or lease a property for a minimum annual rent of €16,000 to be held for at least 5 years and an investment of EUR 150,000 worth of stocks, bonds, debentures, special purpose vehicles to be held for at least 5 years A contribution of EUR 650,000 to the Maltese Government, which is deposited in the National Development and Social Fund. St Lucia (2016) Investment of at least USD 300,000 in an approved property project to be held for at least 5 years or investment of USD 3.5million in an approved business project.

A donation of USD 100,000 to St Lucia National Economic Fund (further fees for spouse and additional dependents) Turkey (2017) Minimum USD250,000 investment in a property to be held for at least three years or minimum capital investment of USD500,000; or USD 500,000 in a Turkish bank or government bonds (for at least three years)

N/A Note: Compiled from government sources on the Internet (as of September 2010). Cyprus suspended its program as of November 1, 2020.


Christophe Lucarz

Marco Mattavelli

Matthieu Wipliez

Ghislain Roquier

Mickaël Raulet

Jörn W Janneck

Ian D Miller

David B Parlour

Dataflow/Actor-Oriented language for the design of complex signal processing systems

Signal processing algorithms become more and more complex and the algorithm architecture adaptation and design processes cannot any longer rely only on the intuition of the designers to build efficient systems. Specific tools and methods are needed to cope with the increasing complexity of both algorithms and platforms. This paper presents a new framework which allows the specification, design, simulation and implementation of a system operating at a higher level of abstraction compared to current approaches. The framework is base on the usage of a new actor/dataflow oriented language called CAL. Such language has been specifically designed for modelling complex signal processing systems. CAL data flow models expose the intrinsic concurrency of the algorithms by employing the notions of actor programming and dataflow. Concurrency and parallelism are very important aspects of embedded system design as we enter in the multicore era. The design framework is composed by a simulation platform and by Cal2C and CAL2HDL code generators. This paper described in details the principles on which such code generators are based and shows how efficient software (C) and hardware (VHDL and Verilog) code can be generated by appropriate CAL models. Results on a real design case, a MPEG-4 Simple Profile decoder, show that systems obtained with the hardware code generator outperform the hand written VHDL version both in terms of performance and resource usage. Concerning the C code generator results, the results show that the synthesized C-software mapped on a SystemC scheduler platform, is much faster than the simulated CAL dataflow program and approaches handwritten C versions.

I. INTRODUCTION

With the unbounded increase of signal processing systems complexity made possible by both the advances in algorithm theory and by new generations of silicon technology, digital systems designers need new tools for the design of efficient systems employing "reasonable" design resources. Increasing the level of abstraction has always been a solution to appropriately handle the increasing complexity of systems design. Transistors, gates, VHDL and Intellectual Property (IP) blocks are example of different abstractions layers which have been successfully introduced in the past with the attempt of easing the design of more and more complex systems. In the authors opinion the current new challenge is not only to add a new abstraction layer, but also to close the gap between the specification and the implementation layers. Such gap, in the recent years, has been tried to be filled by using C/C++ reference implementations of the specifications. However, the path from such specifications expressed as generic C/C++ reference SW to gate design has shown to be harder to be efficiently accomplished. One of the main reasons of such difficulty is the fact that C/C++ do not provide the operators that enable to naturally express parallelism, data flows and other fundamental architectural features without adding a huge amount of low level programming details. In other words the operators are defined at a level that is by, far too, low compared to the one at which a designer would like to express his architectural ideas. Also other approaches and methods aiming at closing the gap from specification to synthesis have yet to deliver on their promise. Several methodologies based on using UML, different variants of C/C++ (i.e streamC [START_REF]Streamc language specification[END_REF]) combined with SystemC/TLM library at different levels of the design flow are used. Some of them make use of exploration tools, simulators and code generators which can output hardware and software code specific to FPGA or other processor platforms, mainly using VHDL and C. Section II briefly reviews these different approaches and methods for building digital systems.

This paper presents a new design framework, currently in its early phase of development, based on CAL language, an actor and dataflow oriented language designed for the specification of complex signal processing systems. The new framework includes: a simulator of the system specified by CAL, a hardware generator for the direct synthesis of HDL and a software generator for the synthesis of C from CAL. The paper explains why and how this framework is a very promising approach for the design and development complex heterogeneous processing systems.

Section 1 introduces the CAL language, a dataflow and actor-based language that constitutes a very interesting candidate to support a design flow for designing complex signal processing systems. The major features of the new approach are simplicity, conciseness and expressiveness. Modelling systems in a concise and simple way is a good starting point, but at the same time enabling the automatic generation of efficient code is an extremely challenging step. Sections IV and V show how efficient hardware and software code can be generated directly from CAL language system descriptions.

Section VI discusses the reasons for which CAL language and the associated framework are a good approach to support a design flow for building complex heterogeneous systems.

Section VII concludes the paper.

II. RELATED WORK

This section provides a brief overview of the current design flows based on UML, SystemC, and C/C++. A comprehensive overview of the state of the art of system level modeling can be found in [START_REF] Sangiovanni-Vincentelli | Quo Vadis, SLD? Reasoning About the Trends and Challenges of System Level Design[END_REF].

Although UML was originally conceived for modelling large software systems, Kukkala et al. [START_REF] Kukkala | Implementing a wlan video terminal using uml and fully automated design flow[END_REF] developed a design flow for multiprocessors Systems on Chip (SoC) by using UML 2.0 models as the starting point of the design flow. UML models (i.e. application, platform and mapping models) are written according to the experience of the designers. However, there is limited support for the elaboration of UML specifications. When building a system from monolithic C/C++ specifications (such as one of the the MPEG reference softwares for instance) UML models must be completely written by hand. This task is very time-consuming and error prone. Furthermore, according to [START_REF] Thomas | Mda: revenge of the modelers or uml utopia?[END_REF], "UML 2.0 lacks both a reference implementation and a human-readable semantic".

Modelling HW using a high level description languages such as SystemC can be a solution for representing functionality, concurrency, communication, software and hardware components at different (system) levels of abstraction. A language modelling complex systems should also provide a support for analysis and synthesis. SystemC is mainly used for simulation because it is not synthesisable in its whole generality. In practice, it can be reduced for ensuring the use of a synthesizable subset. The problem is that this subset of the language is placed at a quite low level of abstraction. Simulation capabilities at a high level of abstraction are an interesting feature of SystemC, but during the implementation step, the designer is forced to re-write the code using only the synthesisable subset. Such operation is a time consuming and error-prone task. In a nutshell, it is hard to use SystemC as a high level design language because in general it is not possible to implement directly systems just developing at high level the system specification.

Several tools propose a direct conversion of C code into VHDL. C-based methodologies for modelling systems lack concurrency and a concept of time. Hardware is inherently parallel and time is essential to represent its behaviour accurately, especially for real-time embedded systems. The main problems of using C as a Hardware Description Language are discussed in detail in [START_REF] Micheli | Hardware synthesis from c/c++ models[END_REF] and [START_REF] Micheli | The olympus synthesis system[END_REF]. In conclusion, the lack of intrinsic concurrency and the concept of time as well as the way communication mechanisms are written in imperative languages are the main limitations and drawbacks of C or similar languages for hardware representation.

III. CAL A LANGUAGE FOR ALGORITHM AND ARCHITECTURE SPECIFICATION

The more important features that system designers would like to find in a design language would be the capability of representing both algorithm and architecture at a single level of abstraction. Unfortunately, it is difficult to specify an algorithm at a high level of abstraction and at the same time being able to deduce from such description an efficient low level representation. How can high level and low level constructs be combined into a single language? Furthermore, such language should support full simulation of the system behaviour. Thus, designers have been forced to use several languages to represent complex algorithms at different levels of abstraction during the entire design flow. Generic C, architectural C, SystemC, synthesizable SystemC is a possible first stage of a design methodology. The main drawback of such multistage approaches is how to implement the conversions between all these languages avoiding resource consuming hand re-writing [START_REF] Thomas | Mda: revenge of the modelers or uml utopia?[END_REF]. Compilers often support only a subset of the languages, making the different conversions between the languages a headache! Thus, the reduction of the number of languages and abstraction levels composing a design flow is a fundamental issue. Ideally, the unique language transformation should be a direct translation from the high level language down to an implementation language such as C, VHDL or Verilog.

Abstract languages do not often support simulation capabilities and architectural representations are available at too low levels of abstraction. Standard imperative languages do not express easily parallelism. These facts reduce considerably the set of possible candidates. The new actor/dataflow oriented language called CAL has been specifically developed so as to support the features discussed above.

A. CAL language

CAL is a dataflow and actor oriented language that has been recently specified and developed by one of the authors of this paper as a subproject of the Ptolemy project at the University of California at Berkeley. The final CAL language specification has been released in December 2003 [START_REF] Eker | CAL Language Report[END_REF]. CAL describes algorithms by using a set of encapsulated dataflow components called actors communicating with each others. An actor is a modular component that encapsulates its own state. The state of any actor is not shareable with other actors. Thus, an actor cannot modify the state of another actor. The only interaction an actor has with another actor is only thought inputs and outputs ports. The behaviour of an actor is defined in terms of a set of actions. The operations an action can perform are to consume (read) input tokens, to modify internal state, to produce output tokens. The topology of the connections between actors input and output ports constitute what is called a network of actors. It is expressed by using an XML dialect known as network language (NL) that also includes the possibility to includes attributes (i.e. parameters) that may be different for the instantiation of the same (parametric) actor in a network of actors. Each action of an actor defines the kind of transitions that internal states can undergo and actions can be fired under specific conditions: (1) the availability of input tokens, (2) the value of input tokens, (3) the state of the actor or (4) the priority of that action. In an actor, the operations are executed sequentially. The execution of actions follows the following cycle:

1) Determine, for each action, whether it is enabled, by testing all the conditions specified in that action. It depends on the availability of token(s) at the requisite input(s), the value of input tokens, the state of the actor and the priority of each action. 2) If one or more actions are enabled, pick one of them to be fired next; 3) Fire that action. 4) Go to [START_REF]Streamc language specification[END_REF]. The transitions of an actor are purely sequential: actions are fired one after another. At the network level, the actors are completely independent and can work concurrently, each one executing their own sequential operations. Figure 1 The selection order and the firing conditions for actions form the core of the design of an actor. CAL provides a number of constructs for describing action selection, which include guards (conditions on the values of input tokens and/or the values of actor state variables), a Finite State Machine and priorities (actions may be related to each other by a partial priority order). The order of execution of the actors is in general not known a priori. CAL provides a great flexibility to schedule action execution according to the particular requirements and constraints of the targeted device chosen for the final implementation.

CAL language very naturally allows also hierarchical system design. Each actor can be specified as a network of actors. This approach facilitates modularity, where the internal specification of any actor can be modified without impacting other actors.

B. Goals and features of CAL language

Ease of use CAL is a true programming language and not an intermediate format to automatically generate code. The notation is convenient to write, with consistent syntax rules, keywords, and structures.

Minimal semantic core CAL language is built on a very small set of semantic concepts. It simplifies compiler construction when transforming any program into an equivalent program in the core language. Thus for the compilation to any given platform, a code generator is needed for the specific implementation language.

Implementation independence and retargetability The first target for CAL actors was the Ptolemy II platform [START_REF] Eker | Taming heterogeneitythe ptolemy approach[END_REF]. A complete framework (Open DataFlow) is currently being developed for simulating CAL networks and for generating hardware and software code [START_REF]Open dataflow sourceforge project[END_REF]. OpenDF is built under the Eclipse environment. It makes these tools available for a large set of operating systems. CAL models are technology and architecture agnostic. Thus, it makes possible to design and simulate models very quickly using [START_REF]Open dataflow sourceforge project[END_REF]. Designers do not need special hardware or libraries to design their own system in CAL. The implementation of CAL models is done by means of appropriate hardware and software code generators described in more details in the following sections.. Once the CAL model is defined, the user can simulate it using the OpenDF simulator [START_REF]Open dataflow sourceforge project[END_REF]. The user can generate software code and hardware code from the CAL model. These code generators are detailed in section IV and V respectively.

C. Framework infrastructure

IV. SOFTWARE SYNTHESIS

A. Semantics of CAL dataflow

The system behavior of a dataflow program is determined by the interactions between actors (i.e. exchange of data tokens). Such interactions are governed by a Model of Computation (MoC) that defines which scheduling policies can be used to fire actors. The CAL language is not related to any particular dataflow MoCs. Indeed, several forms of dataflow exist to interpret the network from the general dataflow process network (PN) [START_REF] Lee | Dataflow Process Networks[END_REF] model with multiple firing rules to the more restrictive synchronous dataflow (SDF) one [START_REF] Lee | Static scheduling of synchronous data flow programs for digital signal processing[END_REF], [START_REF] Shuvra | Synthesis of embedded software from synchronous dataflow specifications[END_REF]. CAL extends the model in [START_REF] Lee | Dataflow Process Networks[END_REF] by : 1) state within actors, 2) multiple overlapping (non-joinable in the parlance of [START_REF] Lee | Dataflow Process Networks[END_REF]) firing rules, and 3) priorities among firing rules. CAL actors often contain multiple actions and priorities, FSM or guards that lead to state-dependent or conditional execution. Therefore most of the CAL actors in the library are closer to the PN model which is then chosen (as a first milestone) for developing the tool described in this paper. When the PN model is chosen to interpret CAL networks, any environment which supports multithreading may be chosen for implementation. For instance, it can be done Fig. 2. The framework infrastructure using POSIX threads by translating CAL actors into threads and by replacing connections with FIFOs. However, it is necessary to develop a scheduler and low-level considerations such as communication or actual scheduler implementation, make this solution time-consuming and error prone. Another approach for PN implementation is provided by the Sys-temC1 standard whose simulation environment permits highlevel programming, well-adapted to functional verifications. A PN-oriented SystemC model is expressed as a network of modules communicating with each other via blocking FIFOs (with an additional way to support token availability). Note that Cal2C does not intend to use SystemC as an hardware description language, but only as a convenient PN modeling and simulation environment. Moreover, this work is a first step to an efficient "pure C" code generation (closer to an SDF model than a PN one). In short, the software synthesis from a network of CAL actors produces several files as illustrated in Figure 3. Each NL network is translated into a header file where FIFOs, modules and sub-networks are instantiated and connected. CAL actor translation is done in 2 different parts: the actor code (actions, functions, procedures) to express the functionality and the action scheduler (priorities, FSMs, guards) to control the execution. Finally an additional file is created to instantiate the top network and to launch SystemC simulation.

B. C code generation: Actors

Actor code translation: Translating the CAL actor code produces a single C file wherein functions, procedures and actions are translated. however, C language and compilers impose limitations on the translated code. For example, (1) distinct functions should have different names to avoid linking problems, even if they are originally placed in different actors. Another challenge is (2) the difference of programming paradigm between the source and the target language: CAL allows functional constructs that have no direct equivalent in C. The action translation process starts with an Abstract Syntax Tree (AST) issued from the CAL source code, and modifies it as needed to satisfy the previous requirements. Function names are prefixed with the actor name to prevent any potential name clashes; actor parameters are replaced by their values (when constant) or transformed to local variables otherwise; actions are converted to functions where input and output patterns become parameters. Finally, actor declarations are ordered by dependencies between locals, so that a variable or a function is defined before being used. At this point, the Cal2C generator converts the AST to λ-calculus, applies Damas-Milner W-algorithm [START_REF] Damas | Principal type-schemes for functional programs[END_REF] to it, and augments the AST with the type information returned. Types are necessary for correct C code generation, and type-dependent transformations. Functions that return lists are "in-lined", and list sizes are computed. The transformed CAL AST is expressed in the C Intermediate Language (CIL) [START_REF] Necula | CIL: An Infrastructure for C Program Analysis and Transformation[END_REF], where CAL functional constructs are replaced by imperative ones. C code is generated by calling the pretty-printer module included in the framework.

An example of the CAL actor code translation process is illustrated on figure 4. Figure 4(a) reports an "action" extracted from the Inversequant actor of the RVC reference MPEG4-SP decoder, and figure 4(b) reports the corresponding generated C code. The resulting code presents a function whose name is composed of the actor name and the action name (requirement (1)). Its parameters are the same of the action's, with an additional pointer to a structure containing the actor variables. The if expression has been transformed to assignments of temporary variables ( if 7, if 8) (requirement (2)). As a matter of fact, function calls have also become assignments of temporary variables ( call 6, call 9) because CIL semantics requires it. The action output expression is translated as a pointer parameter whose value is written at the end of the C function. The synthesized C code shown in figure 4(b) is quite close to the original CAL code and results also reasonably readable by "humans".

Action scheduling: An action scheduler is created to control the action selection during execution. Priorities, guards, token consumption rates and FSM have to be translated to this end. Determining the overall order of action execution is required to have a consistent evaluation of actions that can be fired. Priorities are resolved by sorting actions in a total order and by adding a if-then-else statement around actions wherein the condition is given by the availability of input tokens and the guards conditions. FSMs are resolved using switch-case statement. Finally, the generated file consists of a thread with an infinite loop wherein its body consists of the result of the previous transformations and actions are replaced with their corresponding C functions.

For instance, a downsampler by N is illustrated figure 5(a). It could be written in different and also simpler forms, but in this form the actor enables to highlight key features of the action scheduling translation. The synthesized C++ code is illustrated in figure 5(b).

C. SystemC code generation: Networks

Expressing a network of actors specified by NL in SystemC is relatively straightforward: actor or network instantiations are transformed into module instantiations. There are two semantic differences however: FIFO channels, while implicit in NL, must be explicitly created in SystemC. Broadcast of data from a source to several sinks is transparent in NL, but requires additional logic in SystemC, namely a generic broadcast module.

D. Generation of C code from a CAL description: IDCT and MPEG-4 Simple Profile decoder

So as to validate the correctness of the Cal2C code generation, the first case study is a two-dimensional inverse DCT. The IDCT is a component of all MPEG standard video decoders and is fully specified by the new Finite Precision IDCT Specification [START_REF]Information technology -MPEG video technologies -Part 2: Fixed-point 8x8 inverse discrete cosine transform and discrete cosine transform[END_REF] based on [START_REF] Loeffler | Practical Fast 1-D DCT Algorithms with 11 Multiplications[END_REF]. The algorithm consists of applying one-dimensional IDCT along the row and column axis of an 8×8 pixel block. The network is composed of 2 input ports, 1 output port and 5 different actors; one actor can be instantiated several times in NL. Incoming I shows the number of files of the respective programs. In the code generation process, an actor first is converted into a C file, then into a C++ and finally into a header file. A network of actors simply is translated into a header file while the corresponding C++ file becomes the "main" file. The second row exhibits the corresponding source lines of code (SLOC). The testbed consists of applying a stimulus (streamed by a C-code reference software of MPEG-4 SP decoder) to the top network and verifying the response against an expected result (from the CAL description simulated compared to a "golden reference" streamed by the C-code reference software).

Another synthesized model of a more complex CAL dataflow network simulated with the Open Dataflow environment has also been used to validate the Cal2C tool. The compilation process has been successfully applied to the full MPEG-4 Simple Profile dataflow model written by the MPEG The MPEG4 SP dataflow program is composed of 27 actors. An actor composing a network of actors can be instantiated several times. For instance there are 42 actor instantiations in the MPEG-4 SP dataflow model. The number of SLOC generated is shown in Table III. All of the generated files are successfully compiled by gcc. For instance, the "Parser-Header" actor inside the "Parser" network is the most complex actor with multiple actions. The translated C-file (with actions and state variables) includes 1043 SLOC for actions and 1895 for action scheduling. The original CAL file contains only 962 lines of code as a comparison. In the current version of the HDL generator, each actor is translated separately into HDL and is connected with FIFO buffers in the resulting RTL descriptions. Consequently, no cross-actor optimizations are employed at the current level of development of the tool.

If two actors connected in this manner are specified to belong to different clock domains, an asynchronous FIFO implementation is selected, otherwise a synchronous FIFO is used for compactness of the implementation. Actors interact with FIFOs using a handshake protocol, which allows them to detect when a data token is available or when a FIFO is full.

The translation of each CAL actor into a hardware description follows a three-step process: (a) Instantiation, (b) Precompilation and (c) RTL code generation.

A. Instantiation

The elaboration of the network structure yields a number of actor instances, which are references to CAL actor descriptions along with actual values for its formal parameters. From this, instantiation computes a closed actor description, i.e. one without parameters, by moving the parameters along with the corresponding actual values into the actor as local (constant) declarations. It then performs constant propagation on the result.

B. Precompilation

After some simple actor canonicalization, in which several features of the language are translated into simpler forms, precompilation performs some basic source code transformations to make the actor more amenable to hardware implementation, such as e.g. inlining procedures and function calls. Then the canonical, closed actors are translated into a collection of communicating threads.

In the current implementation, an actor with N actions is translated into N + 1 threads, one for each action and another one for the action scheduler. The action scheduler is the mechanism that determines which action to fire next, based on the availability of tokens, the guard expression of each action (if present), the finite state machine schedule, and action priorities.

To facilitate backend processing, for both hardware and software code generation, the threads are represented in static single-assignment (SSA) form. They interact with the environment of the actor through asynchronous token-based FIFO channels. Their internal communication happens through synchronous unbuffered signals (this is, for instance, how the scheduler triggers actions to fire, and how actions report completion), and they also have shared access to the state variables of the actor.

C. RTL code generation

The final phase of the translation process generates an RTL implementation (in Verilog) from a set of threads in SSA form. The first step simply substitutes operators in expressions for hardware operators, creates the hardware structures required to implement the control flow elements (loops, if-then-else statements), and also generates the appropriate muxing/demuxing logic for variable accesses, including the Φ elements in the SSA form.

The resulting basic circuit is then optimized in a sequence of steps.

(a) Bit-accurate constant propagation. This step eliminates constant or redundant bits throughout the circuit, along with all wires transmitting them. Any part of the circuit that does not contribute to the result will also be removed, which roughly corresponds to dead code elimination in traditional software compilation.

(b) Static scheduling of operators. By default, operators and control elements interact using a protocol of explicit activation-e.g., a multiplier will get triggered by explicit signals signifying that both its operands are available, and will in turn emit such a signal to downstream operators once it has completed multiplication. In many cases, operators with known execution times can be scheduled statically, thus removing the need for explicit activation and the associated control logic. Figure 6 shows the quality of result produced by the RTL synthesis engine for a real-world application, in this case an MPEG-4 Simple Profile video decoder. Note that the code generated from the high-level dataflow description actually outperforms the VHDL design in terms of both throughput and silicon area for a FPGA implementation.

VI. DISCUSSION

In this paper it has been shown that CAL, at the same abstraction level, can yield system specifications for direct SW and HW generation. This is made possible by several interesting properties which not only provide appropriate answers at the problem of finding a language that specify systems at high level, but that can also be extremely useful for facing the challenges of next generation digital systems.

Expressing concurrency The intrinsic cability of CAL operators and construct to describe and easily fit concurrent problems make CAL actor-modeling an excellent fit for system design of parallel algorithms and streaming or data dominated applications.

Compactness The MPEG-4 Simple Profile decoder has been manually implemented in different languages such as C/C++, VHDL and CAL. The full implementation is composed of approximately 4000 lines for CAL, 15000 lines for VHDL, 4100 for an optimized version in C/C++. It shows how concise CAL is, but at the same time concurrency and data dependencies are clearly exposed and by raising the level of abstraction of constructs and operators, CAL needs less lines of code to fully describe a given algorithm. Conversely CAL is not overloaded with implementation details and such feature is a clear advantage. CAL focuses only on the description of the algorithm itself and how data is generated and consumed by the different components. Implementation details such as scheduling of the operations are let to code generators.

Analysis CAL language allows the analysis of an actor and networks of actors. For the definition of the actors, CAL provides statically analyzable information about their behavior, such as the number of tokens it produces and consumes in each firing, the necessary conditions for their firing, on what depend those conditions. . . These information are very useful for effectively schedule, compose, and implement those actors in the final implementations.

Portability CAL specifies algorithms and defines their associated data flow models in a concise and clear way. CAL models are completely independent from final implementation. Thanks to this independency, it eases the integration, exchange and the development of actors. Different implementation for several targets can be built easily from these models. The encapsulation property of the actors is very convenient: global variables do not exist, making the integration of external actors (not written by the designer himself) in the design much easier.

Simplicity of actor design CAL offers a compact, clear and precise semantics, which is tailored to the constraints of actor design and thus facilitates readability and maintainability of the actors. The ease of programming is also necessary to make the language accepted in the scientific community.

Hardware and Software code generation The CAL language is a good starting point for both hardware and software code generation.

The results presented in this paper and in [START_REF] Janneck | Translating dataflow programs to efficient hardware: an mpeg-4 simple profile decoder case study[END_REF] show that efficient hardware code can be generated directly from CAL models. The results show the quality of results produced by the RTL synthesis engine for a real-world application (MPEG-4 Simple Profile video decoder). The code generated from the high-level dataflow description actually outperforms the VHDL design in terms of both throughput and silicon area.

C code can also be generated from CAL models. The results presented in this paper and in [START_REF] Wipliez | Code generation for the MPEG reconfigurable video coding framework: from CAL actions to C functions[END_REF] show significant improvements compared to CAL dataflow simulation with the Open Dataflow environment [START_REF]Open dataflow sourceforge project[END_REF]. The compilation process has been successfully applied to the same MPEG-4 Simple Profile video decoder. The synthesized software (10600 lines of code) is faster than the CAL dataflow simulated (about 20 frames/s instead of 0.15 frames/s), and close to real-time for a QCIF format (25 frames/s) on a standard PC platform. It is interesting to notice that the model is scalable: the number of macro-blocks decoded per second remains constant when dealing with larger image sizes.

CAL is particularly well suited for describing signal processing systems which are intrinsically data-driven. It is not by chance that CAL language has been chosen by the ISO/IEC standardization organization in the new MPEG standard called "Reconfigurable Video Coding (RVC)" (ISO/IEC 23001-4 and 23002-4). RVC is a framework allowing users to define a multitude of different codecs, by combining together actors (called coding tools in RVC) from the MPEG standard library that contains video technology from all past standards (i.e. MPEG-2, MPEG-4 etc, etc ) . The reader can refer to [START_REF] Lucarz | Reconfigurable media coding: A new specification model for multimedia coders[END_REF] for more information about RVC. CAL is used to provide the reference software for all coding tools of the entire library. The essential elements of the RVC framework, besides the tool library, include a Decoder Description expressed in an XML dialect which describes in the architecture of the decoder by specifying the connections between the different actors, a Bitstream Schema (BS) which describes the structure, the organization of the data in the bitstream and implicitly defines the parser needed for the specific decoder reconfiguration.

VII. CONCLUSION AND FUTURE WORK

This paper describes a framework based on CAL data flow language that includes a simulator and SW and HW code generators. CAL data flow models results particularly efficient for specifying signal processing systems in a very synthetic form compared to classical imperative languages. Moreover CAL models can be developed to describe architectural features of the desired implementation, thus enabling the designer to work for both algorithm and architecture specification at the same level of abstraction. Hardware and software code generators then provide the implementation of the actors and associated network of actors on different targets (processors or FPGA). CAL succeeds in unifying different levels of abstraction in a single layer at which specification, design space exploration and efficient implementation can be developed. CAL is very expressive and concise. It exposes clearly the intrinsic parallelism of the algorithm by means of the notion of encapsulated actor processing and explicit data dependencies in the actor network. The first promising results obtained by this framework for modelling systems and generating software/hardware implementations, and the recent adoption by ISO/IEC MPEG of CAL as a the new specification formalism for the library that covers in modular form all video algorithms from the different MPEG video coding standards, shows that CAL is an appropriate language for supporting design flows aiming at building complex heterogeneous systems from high level system specifications. Concerning future works and extension of the framework they include the evolution of the software and hardware code generators in terms the extension of the subset of CAL language supported by the two code generators, the development of scheduling tools beyond the SystemC scheduler for mapping on multicore platforms and the evolution of the current Open DataFlow environment with more accurate and extended profiling and debug tools.

  illustrates a CAL model in general and the reader can find examples of CAL actors in figures 4 and 5(a).

Fig. 1 .

 1 Fig. 1. Illustration of a CAL model

Figure 2

 2 Figure 2 presents the general framework infrastructure.Once the CAL model is defined, the user can simulate it using the OpenDF simulator[START_REF]Open dataflow sourceforge project[END_REF]. The user can generate software code and hardware code from the CAL model. These code generators are detailed in section IV and V respectively.

Fig. 3 .

 3 Fig. 3. Cal2C compilation process

  Fig. 4. C translation of a CAL action

Fig. 5 .

 5 Fig. 5. Action scheduling (FSM) of CAL actor

Fig. 6 .

 6 Fig. 6. Hardware synthesis results for an MPEG-4 Simple Profile decoder. The numbers are compared with a reference hand written design in VHDL.

  tokens from IN port are inverse-quantized coefficint and a token from

	actor downsampler (N) In ⇒ Out :
	count := 1;
	schedule fsm pass:
	copy	( pass ) --> discard;
	discard ( done ) --> copy;
	discard ( skip ) --> discard;
	end
	priority
	done > skip;
	end
	end
		(a) CAL downsampler
	struct downsampler_vars {
	int count;
	int N;
	};
	void downsampler::process() {
	int fsm_state, _call_6, _call_7,_out_1;
	struct downsamplerN_vars _actor_vars;
	_actor_variables.count = 1;
	fsm_state = 1;
	while (1) {
	switch (fsm_state) {
	case 1:
	_call_6 = In->get();
	downsampler_pass(&_actor_vars, _call_6, &_out_1);
	Out->put(_out_1);
	fsm_state = 2;
	break;
	case 2:
	if (_actor_vars.count == _actor_vars.N) {
	downsampler_done(&_actor_vars);
	fsm_state = 1;
	} else {
	_call_7 = In->get();
	downsampler_skip(&_actor_vars, _call_7);
	fsm_state = 2;
	}
	break;
	}
	}
	}
		(b) Synthesized action scheduler

pass: action In: [x] ⇒ Out: [x] end done: action ⇒ guard count = N do count := 1; end skip: action In: [x] ⇒ do count := count + 1; end

  Memory access optimizations. Arrays are mapped to Block RAMs (BRAM) for FPGA implementation. These usually small RAM blocks (typically 18 kBits) are distributed across the FPGA, and can be ganged up to form larger memories, or a number of small arrays may be placed into one BRAM. Furthermore, BRAMs usually provide two or more ports, which allows for concurrent accesses to the same memory region. Based on an analysis of the sizes of arrays and the access patterns, the backend maps array variables to Block RAMs, and accesses to specific ports. (d) Pipelining, retiming. In order to achieve a desired clock rate, it may be necessary to add registers to the generated circuit in order to break combinatorial paths, and to give synthesis backends more opportunity for retiming.

				In case operands arrive
	with constant time difference, a fixed small number of
	registers can be inserted into the path of the operand that
	arrives earlier.
	(c) Size	Speed Code size Dev. time
		slices, BRAM kMB/S	kLOC	MM
	CAL	3872, 22	290	4	3
	VHDL	4637, 26	180	15	12
	Improv.	1.2	1.6	3.75	4
	factor

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