Xiaochun Ye
email: yexiaochun@ict.ac.cnvhnguyen

Van Hoa Nguyen

Dominique Lavenier
email: lavenier@irisa.frfandr@ict.ac.cn

Dongrui Fan

Efficient Parallelization of a Protein Sequence Comparison Algorithm on Manycore Architecture

This paper introduces the Godson-T manycore architecture and demonstrates the efficiency of its synchronization mechanism through a computation intensive bioinformatics application: the comparison of protein banks. The parallel part of the protein sequence comparison algorithm can nearly get a linear speed-up thanks to a fine tuning of the synchronization mechanism provided by the Godson-T chip.

Introduction

In bioinformatics, one of the basic tasks is to compare genomic sequences. There are two main families of applications. The first one is devoted to the search of large databases. The second family concerns large bioinformatics treatments made on the newly data available every day. In that case, sequence comparison is often one of the first operations which are performed on raw data before more complex processing.

Biotechnology improvement in the sequencing area has led to a huge increase in the size of genomic databases such as GenBank and UniProt protein database. Being able to process these data as fast as possible, represent one of the current challenges in bioinformatics. More precisely, comparing sequence means extracting similar zone between sequences. The difficulty is that we do not know both the location and the size of these similar zones. Many algorithms have been proposed to solve this problem, including Smith-Waterman algorithm [START_REF] Smith | Identification of common molecular subsequences[END_REF] and some other powerful heuristics ones such as Blast [START_REF] Altschul | Gapped BLAST and PSI-BLAST : A new generation of protein database search programs[END_REF] and Fasta [START_REF] Pearson | Improved Tools for Biological Sequence Comparison[END_REF].

The algorithm we used in this paper belongs to the seed heuristics algorithm family. It has been developed at IRISA and specifically designed for various parallel platforms including multicore/manycore, FPGA and GP-GPU (graphics boards). It is also oriented toward intensive protein sequence comparison, and not for searching genomic banks. Then, its primarily goal is to compare two banks of protein sequences and to generate alignments where similar zones have been detected. The two protein banks are first loaded and indexed into the computer's main memory for optimizing the search process. However, for large banks, this process can take hours of computation. It is thus extremely interesting to evaluate the behavior of this algorithm onto parallel hardware.

During the last few years, there have been different parallel methods of sequence comparison algorithms. However, few implementations use manycore architecture, while manycore has been more and more popular at the same time. In this paper, we focus on a novel manycore architecture named Godson-T [START_REF] Tan | Experience on Optimizing Irregular Computation for Memory Hierarchy in Manycore Architecture[END_REF][START_REF] Huang | Architecture Supported Synchronization-Based Cache Coherence Protocol for Many-Core Processors[END_REF], and show that the parallel part of the algorithm perfectly suits with the thread programming model of the Godson-T processor.

The Godson-T Architecture

As depicted in figure 1, a Godson-T chip has 24 computing tile nodes, 1 synchronization node, 4 IO controllers, and 4 memory controllers. The L2 cache is grouped into 4 banks. The 25 nodes are arranged in a 2D-mesh network, which provides both high bandwidth and fine scalability.

Figure 2 shows the architecture of one computing node: it consists of 4 processing cores, two L1 Dcaches and one L1 I-cache. They are connected by a crossbar which provides a low-latency and highbandwidth communication within each node. Besides the L1 cache, each node also has a SRAM bank which can be configured as a scratchpad memory (SPM) with very low access latency. SPM can be totally controlled by programmer. It can be used to speedup the access of frequently used data or to exploit the locality of some irregular computations.

Computing node

In addition, Godson-T proposes a rich set of hardware to support synchronization. The way to use Acquire/Release (or Lock/Unlock) operations is similar to those based on shared memory access. With this mechanism, all the Acquire/Release operations can be recorded in the lock manager inside the chip. And this is much faster than traditional Acquire/Release operations which need additional memory accesses.

Godson-T uses a scope consistency (ScC) [6] memory model. Using the Godson-T hardware lock manager, we implement a lock-based cache coherence which is much simpler than snoopy-based or directorybased one. The L1 cache is write-through and the L2 cache is write-back. If it is the first time to read a shared variable after Acquire, Godson-T will always fetch it from L2 cache and then update the old value in L1 cache if there is an old copy there. This ensures the cache coherence among all the processing cores.

Protein Sequence Comparison Algorithm

This algorithm is mainly composed of 5 stages as shown in figure 3. Stage 1 makes indices for the two banks: each bank is stored into the computer's main memory using a specific data structure allowing fast retrieval of short words of length 4, called seeds. Stage 2 enumerates all the 20 4 seeds (there are 20 different amino acids in a protein) and for each of them constructs 2 blocks of substrings: block bk1 contains substrings extracted from index1 and block bk2 contains substrings extracted from index2. A substring corresponds to neighboring amino acids around the seed, typically 40 amino acids. Stage 3 considers all possible pairs of substrings from bk1 and bk2 and starts the computation of an alignment by extending

Parallelization and Performances

Clearly, an efficient parallelization has to target stage 3 and stage 4. Actually, for each seed, stage 2 to stage 4 can be processed independently. So we make each processor fetch a different seed and perform the corresponding stages (stage 2, 3, and 4).

Besides the serial components of the algorithm, there are 3 other factors which will affect the speed-up:

(1) Synchronization overhead. This mainly comes from the Acquire/Release pairs used when the thread fetches a new word from the seed dictionary. We find that more than 90% of the entries in the seed dictionary are empty because there is no hit in both of the two banks. We'd better get rid of them first in order to avoid the unnecessary Acquire/Release pairs and decrease the lock competition among threads. (2) Memory contention. This algorithm is very cache-friendly thanks to the construction of neighboring blocks in stage 2. Different numbers of threads almost cause the same average percentage of time waiting for data access over the parallel part. So it is not a problem for our algorithm. (3) load balancing. This is very critical for the performance of parallelization, because the total parallel execution time is dependent on the longest running thread. We find out that there is a good chance that matches of some special words will be bursty. There are always some words which have much more computation than others, and these words may lead to uneven computation in both stages 3 and stage 4.

The parallel algorithm is depicted in figure 4. A main thread performs sequentially stages 1 and 5 while stages 2, 3 and 4 are parallelized on P slave threads.

The main thread starts by indexing the two banks. Then, it initializes 3 shared variables which will be used by the slave threads. P slave threads are then launched for executing the stages 2, 3 and 4. After that, the main thread waits for all slave threads to finish. Each slave thread returns a list of alignments which are merged into the T1 structure. The algorithm finishes similarly to the sequential algorithm: results are sorted before displayed.

Before performing stage 2, a slave thread has to get a unique seed number through the Acquire/Release pair. To minimize the Acquire/Release overhead, we discard all the redundant seeds in the main thread.

After getting a seed number, a slave thread constructs 2 neighboring blocks of substrings and performs ungapped extension. Results are stored in the internal structure t0_p. The next step is to move these results to the shared structure T0. Again, an Acquire/Release lock is used to reserve K places in T0, if K is the number of successful extensions to be stored. The idx1 variable is updated consequently.

In stage 4, to solve the load balancing problem, we re-divide all the elements in T0 among threads and make each thread get K elements from T0 dynamically. Before that, we add a barrier for the synchronization.

To be efficient, and to avoid long waiting time for the threads stuck in the barrier, we need to pay attention to the computation load of the loops in stage 3. As we mentioned before, seeds are not equivalent: some of them are largely overrepresented. If one of the last seeds belongs to this category, then the thread in charge of it will finish a long time after the others. To suppress this potential drawback, seeds are first sorted by complexity: seeds involving large computation time are computed first. In such a way, the last seeds require a very small amount of computation and the P threads end nearly at the same time. The overhead induces by the barrier synchronization is thus very small. Note that we have removed all the seeds with no hit before performing the sort operation. Thus the sort time is very small. The second part of the computation deals with stage 4 for computing the final alignments. Each slave thread gets K extensions stored in T0 and processes independently K alignments. Getting the extensions must be controlled by an Acquire/Release pair. However, the same lock doesn't need to be used by all threads. We just want to make sure that the correct value can be extracted from the shared structure. Thus, different locks are used for different threads (lock[p] for thread p), and no thread has to wait.

Main thread index1 = index (bank1) -stage 1 index2 = index (bank2) idx0=idx1=idx2=0; T0 = T1 = Ø discard
Performances have been estimated from a cyclebased event-driven simulator. Two banks of 300 protein sequences have been built. They are extracted from the SwissProt database (release 54.6) which has an average length of 360 amino acids.

The algorithm is simulated with an increasing number of threads, starting from 1 to 64. Each thread captures one computing node. We first measure the lock waiting time, which is the time spent in the various Acquire/Release pairs. The following It can be seen that this time represents a very small fraction of the total parallel execution time. Similarly, we evaluate the average waiting time due to the synchronization barrier. For 64 threads, we get 0.63%; it is even smaller for a smaller number of threads. This small synchronization overhead has an immediate impact on the speed-up we can get from this parallelization. Figure 5 draws the speed-up of the parallel part as a function of the number of threads.

We nearly get a linear speed-up. This comes from the high efficiency of the Godson-T synchronization scheme and the fine scalability of the protein sequence comparison algorithm. If we now consider the global speed-up, including both the sequential part (stages 1 and 5) and the parallel part (stages 2, 3, and 4), we obtain the speed-up shown in figure 6.

The red curve (600 proteins) is the results of simulation of comparison between the two banks of 300 protein sequences. The blue one (100 000 proteins) is an extrapolation according to profiling. For small data set, stage 1 represents a non negligible percentage of the execution time (about 5%). For large data set, stage 1 becomes very small compared to the other stages, increasing the overall speed-up consequently. To get more speed-up, stage 5 need to be revisited in order to process data in a way suitable for parallelism

Conclusion and Perspectives

Our results demonstrate that Godson-T is very efficient in the lock synchronization scheme. The total lock overhead is very small and can be almost negligible when using 64 threads. Our results also show that this algorithm has a fine scalability, and is very suitable to be parallelized. With a fine tuning for the synchronization and load balancing, we achieve a nearly linear speed-up when using 1 to 64 threads.

We only implement a coarse-grain parallelism but it is also possible to use SIMD instructions to accelerate the most computation-intensive part: ungapped alignment. With SIMD support, each core can perform several ungapped alignments by using one instruction.

Note that in addition to protein sequences comparison, our implementation is also suitable for other forms of sequences comparison.

Figure 1

 1 Figure 1. Godson-T chip

Figure 3 .

 3 Figure 3. Sequential algorithm Normally, stage 3 and stage 4 dominate in terms of percentage of the execution time, especially when large banks are involved. When the number of sequences is more than 100 thousands, stage 3 and 4 get 64% and 33% respectively. Stage 5 gets 3%. The consuming time of stage 1 and 2 is almost negligible.

Figure 4 .

 4 Figure 4. Parallel algorithm

Figure 5. Speed-up of parallel part Figure 6 .

 6 Figure 5. Speed-up of parallel part Figure 6. Overall speed-up

  table indicates the rate over the total parallel time:

	# ths	2	4	8	16	32	64
	‰	0.029 0.030 0.030 0.038 0.058	0.38


Olivier Crasset

come

Advantages and setbacks of autonomy for home helpers in direct employment

Advantages and setbacks of autonomy for home helpers in direct employment

The french universal service employment cheque (Cesu) is a system that has existed since 2004 in its current form1 . It allows private individuals to declare and remunerate employees in personal services, including home helpers. This forme of employment is known as direct employment. In this context, the employer pays the employee by a means of payment of his choice and, each month, declares the number of hours worked by filling a form on the dedicated website. Social security contributions are calculated and deducted from his bank account. The wage slip is sent directly to the employee. If the work duration is less than 8 hours per week or 4 consecutive weeks, there is no written employment contract obligation and the online declaration takes the place of a contract. In other cases, a written contract must be drawn up. Except in special cases, this contract is for an indefinite period.

Direct employment represents an important part of the employment of home helpers with so-called vulnerable people2 . Almost two thirds of them work for a private individual3 . A quarter of elderly people with a Personal Independance Allowance4 (APA -allocation personnalisée d'autonomie) employ at least one employee [START_REF] Bressé | Qui sont les particuliers employeurs en perte d'autonomie et leurs salariés ?[END_REF].

Poor and variable working conditions according to employment status

In the home support services sector, the literature describes poor working conditions due to lack of recognition, job insecurity, low and unstable incomes, among other things. Although well documented, this situation remains socially invisible due to the high feminization of the sector. In this activity, 98.5% of which is occupied by women, the professional skills that are used appear to be naturally female and the resulting income is perceived only as a supplement for the household [START_REF] Dussuet | Genre, frontières du travail domestique et marges du salariat. Le cas des aides à domicile[END_REF]. All forms of employment combined, the wage relationship is described as incomplete, i.e. "home helpers do not benefit from the protections of the traditional wage relationship" (Devetter and Messaoudi, 2013: 51). Several attributes of the wage contract are listed by these authors to show its incompleteness. First, the economic risk, which in principle is borne by the employer, is largely transferred to employees because fluctuations in labour demand have a direct impact on their working time, whether upward or downward. Secondly, the expenses related to travel between the homes of the assisted people are not or little paid, as are the travel times. Thirdly, working time is very flexible in the sector. The frequent replacements are related to the arduousness, which is the source of many sick leave, and to the temporary or permanent loss of clients whose health is fragile.

In this context, home helpers, often on a part-time basis, choose between salary and arduousness. An increase in working time results in a relatively greater increase in the constraints that have been described, a decrease in hourly wages and atypical working hours that pose problems in reconciling work and family life. Under these conditions, it is understandable that the sector is facing difficulties in recruiting and has a high turnover (CHORUM -CIDES, 2016).

In their analysis, Devetter and Messaoudi distinguish direct employment in Cesu from two other forms of employment. The first one is the salaried employment in a providing organisation and the second is a form of employment where a proxy organisation provides administrative supervision of the work, even if the elderly person is the official employer. While the situation of all home helpers "borrows a number of features from self-employment (autonomy, frequent plurality of employers, simplified employment contract, in particular)" (ibid., p. 55), work in Cesu is the closest thing to it. Indeed, home helpers in direct employment assume the economic risk of the activity in its entirety since their salary may vary according to the employer and the fluctuation in activity is not delayed by the replacements that are possible in the employing organisations5 . In their case, the loss of an elderly person is more frequently accompanied by a decrease in salary. Travel expenses and travel time between two employers are not compensated, nor are other expenses essential to work such as car or telephone. At first glance, their situation as employees in Cesu seems more degraded than that of their counterparts who work in other modes. Nevertheless, the authors mention other facts that nuance the picture. Monthly working time varies less in direct mode than in other cases. They are also less concerned by working in atypical schedules. Finally, for equal working time, the indicator of perceived arduousness is lower for employees in direct employment than for other modes. The authors also observe a "market segmentation logic" that allows directly employed employees to "choose the people they help" and to "limit painful interventions " (ibid., p. 68-69).

These nuanced analyses call for caution. Referring only to Fordist employment standards seems insufficient to gain a detailed understanding of the working conditions of direct employment home helpers. Isabelle Puech (2014) suggests extending the reflection to other aspects of work and questioning the notions of collective, subordination and power relations. We can also try to understand what makes it preferable to "choose" Cesu in a professional career.

Methodological informations

This survey is conducted in the context of the ANR Profam research. Between profession and family, the "frameworks" of work to help the elderly. The purpose of this study is to examine the contemporary transformations of the work environment in support of the elderly. PROFAM's originality consists in jointly analysing all the assistance provided in all its forms (paid or free assistance, family or professional, etc.). It is a question of understanding how the current context affects the quality of the jobs of those who help, how they fit into the family logic of the people being helped. The analysis focuses on three levels : 1° public policies, which are a major determinant of these frameworks ; 2° the activity deployed by private actors (Companies, Associations, Trade Unions,…) ; 3° the experiences of individuals and their families. The part of the survey dedicated to direct employment is based on interviews (home helpers, institutional actors), work observation, analysis of classified ads and consultation of online forums. The respondents reside in a department6 in the West of France. They have at least one person among their employers who receives the Personal Independance Allowance (APA) and who pays them in Cesu.

Working from the perspective of autonomy

The term "autonomy" is polysemic and controversial. Ethymologically, it refers to governing oneself according to one's own laws, but its meaning varies according to the field in which it is used. It is also a central value in contemporary society.

When it comes to elderly people, autonomy is opposed to dependency, the latter being a condition requiring "assistance for the performance of essential acts of life" (Law on Specific Dependence Benefit of 1997). This definition remains widely used despite criticism [START_REF] Ennuyer | Les malentendus de l'"autonomie" et de la "dépendance" dans le champ de la vieillesse[END_REF].

In the sociology of work, the concept of autonomy is not unanimously accepted. Indeed, in a strictly deterministic conception, individual autonomy is unthinkable since agents are driven by forces that exceed them [START_REF] Terssac | Autonomie[END_REF]. If we want to use this term, we must therefore accept the idea that determinisms have a certain elasticity and consider that, in any situation, individuals are always called upon to make certain decisions. The authors who have studied industrial work have shown the ability of workers to develop ways to resist management's injunctions or to remedy the uncertainties of formal rules by complementing them with others. In this context, "autonomy is the ability to conduct oneself according to one's own rules invented on the margins or against the system of official rules" (ibid. p. 49).

Autonomy is also mentioned as a criterion that differentiates paid work from self-employment. Placed in a situation of subordination, and despite the limits that have been indicated, the employee's autonomy is reduced to little because the most important decisions are not his responsibility. On the other hand, the self-employed worker has, at least in theory, the possibility of setting the rules concerning his work himself. In particular, it can decide on its schedules, its customers, the services offered, the prices and the geographical area in which it operates.

Defined by the Labour Code, the borderline between wage employment and self-employment is increasingly uncertain. The term "grey zone" [START_REF] Supiot | Les nouveaux visages de la subordination[END_REF] or "porosity of borders" [START_REF] Célérier | Le travail indépendant : Statut, activités et santé[END_REF] is used to refer to the fact that paid employment now has characteristics close to independence and that some forms of self-employment place the worker in a situation of economic dependence close to subordination.

First, we will see what is the career path that leads these women to opt for direct employment. Then, we will examine to what extent and in what forms their autonomy is deployed. Next, we will describe organisational forms that highlight the collective dimension of autonomy.

The choice of direct employment in a family and professional path : a rejection of work in organisations

With the exception of the youngest (23 years old) who turned to home services from her initial training, the respondents arrived there after having worked in other sectors. The ideal type path is that of a woman who interrupts her professional activity at the time of maternity and, a few years later, seeks to re-enter the labour market while continuing to care for children. To find a job, working hours are crucial because they must be compatible with family life. In concrete terms, they must leave the possibility of accompanying children to school, picking them up when they leave and doing homework with them. The corollary of this criterion is the proximity between the workplace and the home.

The expected income is additional income if the home helper's spouse is employed. But for singleparent families, it is the main household income that is at stake, unless Cesu comes to supplement parttime paid work. This is the case for two respondents, a nurse and a care assistant, who are obliged to supplement their income with night shifts in Cesu to balance their budget.

For these women who are returning to work and whose schedules are constrained by their children's rhythms, working in home help is an option as long as they are not discouraged by contact with the elderly. Indeed, all of them state that they appreciate the relationship with this population. The home help sector is struggling to recruit. It is relatively easy to enter, especially since employers are present throughout the country and no diploma is required. They find their first part-time job there, possibly starting with replacements.

As we have seen, working conditions in home help are difficult in many aspects. But when respondents talk about their work experience in an organisation, another problem is raised unanimously. While these early experiences confirmed their interest in working with seniors, they also introduced them to what they consider to be a form of mistreatment of older people whose lifestyle is not respected. They denounce situations that they consider unacceptable such as "indecent bedtime" (elderly people put to bed at the end of the afternoon), meals dispatched in a few minutes ("18 minutes for a meal is forcefeeding. I wasn't happy with it"). We refer to "the factory", "the line work" and the "ringing cop" when the home helper is notified by a telephone application that she must go to the next customer. This time pressure causes discomfort in the elderly, which is contrary to the ethics of these women who, for the most part, have devoted the preceding years to developing qualities of empathy and patience with the young children they have raised. Like young children, older people have a slow pace that contrasts with the imposed pace of work, resulting in a feeling of abuse that can become unbearable. They are then unable to develop a quality relationship with the people they are helping. However, the well-being of the person being cared for and the human relationship are essential to them, as one of them expresses it here: I had a lot on my mind, but I couldn't help it. So I said, "I'm sorry..." They understood, because I wasn't the only one coming. They said "ah ! The cop rings..." A lot of people called it a cop. "Oh, the cop is ringing!" Some of them were there : "Don't forget to page me! ». They were stressed, the little grannies, because they knew that otherwise they would be charged for the 3 minutes. So it's not liveable for anything, whether it's for us or for them, it's... And then all the time different people every day. We didn't have time to get used to them, and they to us. So every time the poor granny had to get up, show us where the detergents were... How do you expect the person to be well? (Laurence, 45 years old).

The enthusiasm of returning to work is followed by disillusionment, especially since the respondents are fully aware that their schedule is made up of short interventions interspersed with travel, which means that they have to extend their days to generate sufficient income. The hope of finding a job that is compatible with family life is therefore sometimes disappointed. For these and other less frequent reasons7 , respondents decide after a few months to distance themselves from the organisation and work in direct employment. The break may be abrupt or it may be smooth by combining the two forms of employment and gradually reversing the proportions. By their operation, proxy organisations facilitate the combination with Cesu employment.

If these women persevere in the home help sector, it is because their period of employment in an organisation, even if it was unsatisfactory, confirmed their taste for working with elderly people. They are therefore looking for a status that will allow them to continue this activity in good conditions. Some are thinking about creating an association, and then consider that Cesu is the best solution. A "real company", even in the form of a microentreprise 8 is considered too risky 9 .

Knowing professionals in the social or health field, including other direct employed home helpers, is a useful asset to familiarize yourself with this status. To find their first "clients 10 ", some admit to hijacking seniors they met at their former employer's home.

Different ways to introduce yourself to potential employers are used. In addition to business cards placed in local shops (bakery and pharmacy), there are also classified ads placed online, particularly on the Le Bon Coin website. The drafting of this announcement is an act that is taken seriously by the person who makes it because the stakes in terms of employment are linked to a reflection on the professional project. These advertisements refer to professional skills by mentioning past jobs and possible diplomas. They also highlight human qualities such as listening, punctuality and discretion.

They also indicate in which areas people who use them seek to extend their autonomy. Indeed, they mention at least the following three points: the catchment area, the proposed tasks and the tariffs. The proposed conditions are sometimes presented in a firm way ("12 €/hour, minimum two consecutive hours") or more negotiable ("11 €/h" and lower "tariff to be agreed").

The catchment area is not a subject of negotiation. It is delimited once and for all according to a distance beyond which the time and cost of the journey are dissuasive. Small in size, the area is limited to a few communes and rarely extends beyond twenty kilometres around the home.

The services offered include maintenance of the living space, companionship, travel assistance, assistance with getting up and going to bed, preparation and eating of meals, assistance with administrative tasks. They can extend to childcare, home ironing and also to the management of holiday rentals for those residing on the coast.

In the department investigated, the rates vary between 10 and 14 €/h. and are often set at 12 €/h. The more demanding proposals emphasize the possession of a diploma and administrative skills. Not surprisingly, those who offer the lowest rates highlight household chores. The mention of the method of payment in Cesu is sometimes accompanied by other terms and conditions that suggest the possibility of undeclared employment ("Payment: Cesu, cheque or cash").

By moving into direct employment, home helpers seek to work according to rules they set themselves. By defining a catchment area, a list of services and a tariff, they exercise the prerogatives of selfemployment. Of course, they must formulate an offer that is adapted to a local economic market that varies from one place to another, particularly according to its proximity to the coast, a more prosperous area that offers more opportunities.

The respondents state that in seeking employment in Cesu, their objectives are to adopt a work rhythm that is in line with that of the people they are helping, to maintain a quality human relationship with them over the long term, which makes it possible to offer an individualised response to their requests.

8 A sort of microentreprise with simplificated procedure exists in France since 2008 under the name of "autoentreprise". 9 And in any case impossible in the department studied since the necessary approval is not granted to autoentreprises. 10 We use here the term most often used by respondents to refer to their employer.

In short, it is a question of solving the problems encountered during the period of employment in an organisation. This is why the passage to Cesu is described as an emancipatory event that has led to an improvement in the professional situation, in particular because it makes it possible to satisfy the expectations of both parties in terms of the quality of the human relationship. A good relationship with the elderly is an important element in the emotional life of some of the home helpers, some of whom have had difficult family experiences. They must learn to manage this aspect of their work by finding the "right distance" that combines empathy and professionalism, without being overwhelmed or creating dependence on them.

The analysis of the classified ads shows that the autonomy exercised by home helpers who work in direct employment is deployed in several areas : choice of tasks offered, catchment area and price, knowing that these choices are constrained by an economic market that leaves more or less room for negociation. But the ads do not provide a favourable framework for the expression of two other areas of autonomy, namely customer choice and scheduling.

The home helper is free to conclude or not an employment contract with the elderly people she meets. Of course, the opposite is also true. There is therefore a negotiation to be conducted on the definition of this contract which takes place during a first meeting. This is a key moment when each of the parties seeks to know who they are dealing with. Depending on the physical and mental condition of the senior, the negotiation takes place directly with him or with a family member. Home helpers focus on identifying the needs of the person to be helped and understanding their personality. Some are looking to find out what equipment is available in the home that reduces arduousness. The next step is to agree on the definition of the rules of the game. Depending on the power relationship that is established, it is the client or the home helper who imposes conditions such as the definition of a trial period, working hours and situations where they may be modified (medical appointment, absence due to a sick child, vacation periods). But beyond this negotiation, it is a question of knowing if the two people have compatible characters, if each one "feels good" or not his interlocutor. Two contrasting examples indicate the results of these negotiations.

Maëlle has been working in Cesu for 5 years. With a weekly working time that varies between 28 and 35 hours, she considers her schedule to be full. When she loses a client, she chooses a person on her waiting list after considering who the available slot may be suitable for. She imposes a trial period on her new employer during which she ensures that he lets her work in her own way (for exampple with the cleaning products of her choice) and that the relationship with the person is going well (neither intrusive nor distant). She warns that certain situations will justify her absence (for example, a sick child). Its rate is generally 12.5 euros/h., but it can vary between 10 and 15 €/h. depending on the person's resources and the length of the relationship11 .

It's like I'm a little boss of myself. (...) "I choose my schedules, I choose what I do, I choose the people I work with, and therefore with whom I work, and I choose the way I do it. And I choose (...) what allows me to live correctly, the hourly rate. And I choose my holidays and... I'm imposing on them, aren't I? (...) But kindly, after that I try to work it out... (Maëlle, 47 years old)

As she points out in this last sentence, she makes some concessions, but the balance of power is clearly in her favour and she is fully aware of it. This allows her to choose and plan her work as she wishes. If she sometimes exceeds the scheduled working time in order not to interrupt a task, she can also leave earlier if everything is finished. She is the one who takes her employers' medical appointments and easily integrates them into her schedule. The Friday afternoon, referred to as a "safety valve", is an adjustment period reserved for the completion of tasks that have remained outstanding during the week.

On the other hand, Yvette, without a job at the time of the first contact with the family of a very dependent elderly person, accepts a full-time job after having worked a few hours. She will then learn that the elderly person's children tested several employees at the same time before choosing her. She works six days a week. Her work is interrupted from noon to 3pm, while her children, whom she is raising alone, are at school. Then she returns to work until the elderly person goes to bed, around 7 p.m., with frequent episodes where she stays later without being paid for this extra time. When her children are sick, she cannot adjust her schedules and must find someone to take care of them. The reconciliation of work and family life poses problems that are always resolved to the advantage of her employer, as she points out in relation to episodes where she works later than expected : I couldn't see myself leaving her or calling one of the children (of the elderly person saying:) "Come because she's going to need you for half an hour there". That's not possible. So I called my people and told them "you're going to wait for me for a little half an hour, I'll be there soon. (Yvette,59 years old) The few symbolic compensations she receives (small gifts for her children) do not in any way balance a relationship where Yvette is dominated by her only employer. After two years in her service, when she asks for another home helper to take over on Saturdays, her employers terminate her employment contract. At no point in her career did she consider asking to be paid beyond the minimum wage.

I was afraid that... I would be told "if it doesn't suit you, go elsewhere".

These two situations, chosen for their contrast, are explained by the fact that home helpers do not all have the same skills ton bring on the labour market. While Maëlle has a significant amount of academic capital (master's degree in history and a small diploma as an animator), Yvette holds a professionnal diploma 12 and a diploma as a life assistant followed in lifelong learning. In addition, Maëlle is able to offer her clients the facilitation skills she has developed over the course of her professional career. Thus, she organizes shared gardens and teatimes that are highly appreciated by its customers.

More generally, the variety of tasks performed by the respondents is important, whether for the elderly (visits and follow-up in the event of hospitalisation, gardening, small livestock farming in rural areas, computer troubleshooting) or in other sectors (janitorial services for holiday rentals in coastal areas, home ironing). Household tasks are the common task of the respondents, as well as accompanying them to shopping and medical appointments. Performing administrative tasks is a recurrent request to which they respond in a variable way. While the less educated are reluctant to do so and limit themselves to helping with simple documents, others take care of money matters (tax returns, writing bank cheques, withdrawing cash) and complex administrative tasks (requesting a review of the APA, monthly declaration of their own employment, coordinating medical care and even organizing the funeral of a deceased person whose family is away).

Medical procedures and body care are generally performed only by authorized persons, even if there are some shifts in tasks, for example when it comes to supplying the pill box.

Certain administrative and financial tasks are in principle prohibited. Respondents try to respect the law, but some situations lead them to deviate from it in spite of themselves, when they believe that the well-being of the person (in particular his home maintenance) is at this price. In this case, money matters are carefully reported to the senior or his or her family so that there is no doubt about the honesty of the home helper.

Another element that distinguishes home helpers who benefit from autonomy is that they belong to a network of colleagues made possible by a long-standing registration in the territory. Maëlle grew up near where she works, while Yvette recently moved to the region and has never managed to integrate into a network of colleagues. As we will see, belonging to a network promotes successful integration into the labour market.

The collective dimension of autonomy

Like other independent professionals such as craftsmen [START_REF] Roy | Accords de collaboration et réseaux locaux[END_REF] or in direct employment such as nursery assistants [START_REF] Duclos | L'Internet des assistantes maternelles[END_REF], the home helpers interviewed can only work satisfactorily thanks to their integration into professional networks. These generally include a few individuals (2 to 4) who have been dating for a long time on the basis of a sociability of "housewifes" (school, children's sporting activity, community life). They can also meet each other by working for the same employer, which gives them the opportunity to observe each other. This small affinity group of a few individuals in a mutual aid mode constitutes what can be called a set, i.e. a small group of people with close relationships based on common interests.

Entering such a network is essential to find good job offers. Respondents who are removed from it following a house move encounter difficulties and initially only access proposals that are abandoned by others. The insertion in a set provides various advantages. In the foreground, they facilitate replacement in the event of illness or for holidays. They thus take over from the employer organisations that fulfil this role for their employees. Being replaced by someone you trust is also the assurance of finding your job after an absence. Replacements are the entrance door to the sets. Work offers are circulated within them. If a home helper receives a proposal that she does not wish to respond favourably to, she forwards it to others who she trusts. Sets are also sources of information about customers, especially about people with whom it is better to avoid dealing.

At the same time, meetings with professionals in the social and health sector are daily in their workplaces (nurses), in shops (pharmacists), by accompanying their clients to medical appointments (doctors), by completing administrative formalities (social workers). These contacts supply the sets with work offers. Clients and their families are not left out in this social game when it comes to recommending a home help to someone in need.

The social capital thus built is based on good reputation, which is a form of recognition of their work that they often lack. But if word of mouth is the best business card, it can also be the worst, as Sylvie testifies.

It's a double-edged sword, isn't it? So that's why when I recruit -well, when I recruit in quotation marks -when I bring someone in to work, when nurses ask me for it, I'm very, very careful because reputation can be destroyed very quickly. So there are people, for example I think of one or two household helpers who have a vicious tongue, I am very careful. Because it could destroy my reputation and that of my colleagues, and I don't want to. (Sylvie,46 years old) Being known to "seek money", as a person who rushes the elderly or as a "viper's tongue" leads to the exclusion of the person in question. This is why reputation is the subject of constant vigilance and behaviour designed to defuse criticism. Entry into the collective usually begins with replacements, with some people being identified as future colleagues.

There are two or three of them, I'd like them to come and work as independant in the field with me! Because they're people with whom it goes really well! Now, at the welfare committee, I have two in mind, and I told them "but are you sure you don't want to become an employee of a particular employer? You'd have hours!" Because she does a great job, because she's not just cleaning, she also knows how to listen, how to look, how to be discreet and look everywhere at what can happen.... Be attentive to silence, be attentive to the fridge which is empty, to the laundry which is piling up... (Sylvie) This collective autonomy brings many advantages. Well identified by professionals in the sector, the collective makes it possible to centralize relations with these privileged partners. A respondent participates in the definition of APA plans in consultation with the social workers, either by completing the file or by providing important information about the psychological state of the person concerned, the presence of his children or relations with his spouse. In addition, the collective provides beginners with information on employee rights in Cesu and advice in the event of conflict with employers.

As we have seen, home helpers acquire additional autonomy in different areas through direct employment. The result is an increase in social inequalities and some difficulties related to this status. Some problems are well identified, such as the difficulty of enforcing rights against employers who consider themselves clients [START_REF] Devetter | Les aides à domicile entre flexibilité et incomplétude du rapport salarial : conséquences sur le temps de travail et les conditions d'emploi[END_REF]. Other disadvantages, frequently encountered among self-employed workers [START_REF] Crasset | La santé des artisans[END_REF], also arise. First, there are difficulties in stopping work for health reasons. This difficulty is linked to the complexity of the administrative procedures required to obtain a daily payment, which must be carried out with each of the employers. In addition, there is a duty to respect its commitments to preserve its good reputation. If she cannot be replaced by a colleague, the sick home helper will go to work. Secondly, taking a holiday is an additional problem. As paid holidays are included in the monthly salary, it is necessary to set aside provisions throughout the year to build up a reserve, which the most disadvantaged cannot afford. Finally, one respondent reported that it was impossible to obtain a mortgage from her bank, which considered direct employment to be precarious, although the person concerned had been working on permanent contracts for several years.

Conclusion

To understand how the question of autonomy arises among the respondents, it is necessary to consider the path that leads them from motherhood to work in an organisation, then to Cesu. Without a particular predisposition to self-employment, these women do not have an entrepreneurial project. For them, it is a matter of finding a job that offers good working conditions.

The home helpers employed by the organisations already have a certain degree of autonomy. Far from the management staff in their daily practice, they organise themselves as they wish as long as the work planned is carried out on time. Faced with the unexpected and the demands of the elderly, they know how to deal with them. Their autonomy consists in implementing strategies to meet the objectives set by management. They also seek to achieve their own goals by resisting the rules set by management.

Nevertheless, the constraints of working in an organisation require them to work in conditions that are incompatible with their values. The transition to Cesu is experienced as a positive change that allows them to continue working with the elderly whose company they enjoy. When asked about their current employment, it is often in comparison to the period of employment in an organisation that they proceed to point out that aspects that seemed unbearable have been discarded. Finally, it is the mediocrity of the workforce in organisations that serves as a benchmark to assess the new situation. There is nothing to suggest that things are assessed in the same way by employees in Cesu in sectors of activity that offer better quality jobs.

By moving to direct employment, their autonomy is extended to new areas : definition of the catchment area, schedules and rates, choice of customers and tasks offered. This change can potentially bring many benefits if the person has cultural, social resources and skills from previous professional experience that can be mobilized. Without these assets, the competitive market game works and the poorest are at the mercy of their employers when they manage to find one. Some of them may nevertheless be able to reach a set. These informal groups temper social inequalities through mutual support. This collective dimension of autonomy is a common feature of self-employment.

While respondents sometimes feel the benefits of self-employment, they also come close to it through the problems they encounter : difficulties in stopping work, high mental workload, financial insecurity, not to mention the redefinition of the line between work and private life that has not been addressed here. However, they remain protected from the risks associated with owning their work tool, unlike maternal assistance [START_REF] Duclos | L'Internet des assistantes maternelles[END_REF].

While they talk about "clients" to designate their employers, they are well aware that they are employees. Often well informed of the benefits and risks associated with each employment status, they know their rights as soon as they are socialized within a collective. Unions have very little presence in this sector and the collective plays a role in informing about rights and in the ability to enforce them.

The situation described here cannot be generalized to all jobs in direct employmenbt. The home help sector is unique in several dimensions : deteriorated working conditions in the organisations making direct employment more enviable by comparison, a sector in high demand for labour, and a demand supported financially by the APA system. The situation will probably change with the upcoming arrival of Uber-type platforms in personal services.

It exists in the declarative form referred to here and in the pre-funded form that is not addressed. See Cesu's website, https://www.cesu.urssaf.fr/info/accueil.html

The people qualified as fragile are the elderly, handicapped or in need of help with everyday activities.

IAE survey, Drees, 2008, analysed by Devetter and Messaoudi, 2013[START_REF] Bressé | Qui sont les particuliers employeurs en perte d'autonomie et leurs salariés ?[END_REF]

In french, Allocation Personnalisée d'autonomie (APA), a universal allowance for people over 60 years of age with a certain level of dependency

In this text, the term "organisation" refers both to employers in the social economy (associations, municipal mutual aid committees) and private companies in the sector.

Department : an administrative division of the territory which has 95 for Metropolitan France. Social assistance for the elderly is managed at this level[START_REF] Bigoteau | Local welfare systems supporting female employment in Nantes, FLOWS working paper series[END_REF].

Problems with management and supervisory staff, repetitiveness of tasks, confrontation with people who are difficult to manage are discussed.

Some long-standing customers with limited resources have not seen their rates change, while others have taken the initiative to increase the hourly rate.