starpu-max/src/core/perfmodel/perfmodel_history.c

/* StarPU --- Runtime system for heterogeneous multicore architectures.
 *
 * Copyright (C) 2009-2014  Université de Bordeaux 1
 * Copyright (C) 2010, 2011, 2012, 2013, 2014  Centre National de la Recherche Scientifique
 * Copyright (C) 2011  Télécom-SudParis
 *
 * StarPU is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at
 * your option) any later version.
 *
 * StarPU is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * See the GNU Lesser General Public License in COPYING.LGPL for more details.
 */

#include <dirent.h>
#include <unistd.h>
#include <sys/stat.h>
#include <errno.h>
#include <common/config.h>
#include <common/utils.h>
#include <core/perfmodel/perfmodel.h>
#include <core/jobs.h>
#include <core/workers.h>
#include <datawizard/datawizard.h>
#include <core/perfmodel/regression.h>
#include <common/config.h>
#include <starpu_parameters.h>
#include <common/uthash.h>

#ifdef STARPU_HAVE_WINDOWS
#include <windows.h>
#endif

#define HASH_ADD_UINT32_T(head,field,add) HASH_ADD(hh,head,field,sizeof(uint32_t),add)
#define HASH_FIND_UINT32_T(head,find,out) HASH_FIND(hh,head,find,sizeof(uint32_t),out)

struct starpu_perfmodel_history_table
{
	UT_hash_handle hh;
	uint32_t footprint;
	struct starpu_perfmodel_history_entry *history_entry;
};

/* We want more than 10% variance on X to trust regression */
#define VALID_REGRESSION(reg_model) \
	((reg_model)->minx < (9*(reg_model)->maxx)/10 && (reg_model)->nsample >= _STARPU_CALIBRATION_MINIMUM)

static starpu_pthread_rwlock_t registered_models_rwlock;
static struct _starpu_perfmodel_list *registered_models = NULL;

size_t _starpu_job_get_data_size(struct starpu_perfmodel *model, struct starpu_perfmodel_arch* arch, unsigned nimpl, struct _starpu_job *j)
{
	struct starpu_task *task = j->task;

	if (model && model->per_arch && model->per_arch[arch->type][arch->devid][arch->ncore][nimpl].size_base)
	{
		return model->per_arch[arch->type][arch->devid][arch->ncore][nimpl].size_base(task, arch, nimpl);
	}
	else if (model && model->size_base)
	{
		return model->size_base(task, nimpl);
	}
	else
	{
		unsigned nbuffers = task->cl->nbuffers;
		size_t size = 0;

		unsigned buffer;
		for (buffer = 0; buffer < nbuffers; buffer++)
		{
			starpu_data_handle_t handle = STARPU_TASK_GET_HANDLE(task, buffer);
			size += _starpu_data_get_size(handle);
		}
		return size;
	}
}

/*
 * History based model
 */
static void insert_history_entry(struct starpu_perfmodel_history_entry *entry, struct starpu_perfmodel_history_list **list, struct starpu_perfmodel_history_table **history_ptr)
{
	struct starpu_perfmodel_history_list *link;
	struct starpu_perfmodel_history_table *table;

	link = (struct starpu_perfmodel_history_list *) malloc(sizeof(struct starpu_perfmodel_history_list));
	link->next = *list;
	link->entry = entry;
	*list = link;

	/* detect concurrency issue */
	//HASH_FIND_UINT32_T(*history_ptr, &entry->footprint, table);
	//STARPU_ASSERT(table == NULL);

	table = (struct starpu_perfmodel_history_table*) malloc(sizeof(*table));
	STARPU_ASSERT(table != NULL);
	table->footprint = entry->footprint;
	table->history_entry = entry;
	HASH_ADD_UINT32_T(*history_ptr, footprint, table);
}

static void dump_reg_model(FILE *f, struct starpu_perfmodel *model, struct starpu_perfmodel_arch* arch, unsigned nimpl)
{
	struct starpu_perfmodel_per_arch *per_arch_model;

	per_arch_model = &model->per_arch[arch->type][arch->devid][arch->ncore][nimpl];
	struct starpu_perfmodel_regression_model *reg_model;
	reg_model = &per_arch_model->regression;

	/*
	 * Linear Regression model
	 */

	/* Unless we have enough measurements, we put NaN in the file to indicate the model is invalid */
	double alpha = nan(""), beta = nan("");
	if (model->type == STARPU_REGRESSION_BASED || model->type == STARPU_NL_REGRESSION_BASED)
	{
		if (reg_model->nsample > 1)
		{
			alpha = reg_model->alpha;
			beta = reg_model->beta;
		}
	}

	fprintf(f, "# sumlnx\tsumlnx2\t\tsumlny\t\tsumlnxlny\talpha\t\tbeta\t\tn\tminx\t\tmaxx\n");
	fprintf(f, "%-15le\t%-15le\t%-15le\t%-15le\t%-15le\t%-15le\t%u\t%-15lu\t%-15lu\n", reg_model->sumlnx, reg_model->sumlnx2, reg_model->sumlny, reg_model->sumlnxlny, alpha, beta, reg_model->nsample, reg_model->minx, reg_model->maxx);

	/*
	 * Non-Linear Regression model
	 */

	double a = nan(""), b = nan(""), c = nan("");

	if (model->type == STARPU_NL_REGRESSION_BASED)
		_starpu_regression_non_linear_power(per_arch_model->list, &a, &b, &c);

	fprintf(f, "# a\t\tb\t\tc\n");
	fprintf(f, "%-15le\t%-15le\t%-15le\n", a, b, c);
}

static void scan_reg_model(FILE *f, struct starpu_perfmodel_regression_model *reg_model)
{
	int res;

	/*
	 * Linear Regression model
	 */

	_starpu_drop_comments(f);

	res = fscanf(f, "%le\t%le\t%le\t%le", &reg_model->sumlnx, &reg_model->sumlnx2, &reg_model->sumlny, &reg_model->sumlnxlny);
	STARPU_ASSERT_MSG(res == 4, "Incorrect performance model file");
	res = _starpu_read_double(f, "\t%le", &reg_model->alpha);
	STARPU_ASSERT_MSG(res == 1, "Incorrect performance model file");
	res = _starpu_read_double(f, "\t%le", &reg_model->beta);
	STARPU_ASSERT_MSG(res == 1, "Incorrect performance model file");
	res = fscanf(f, "\t%u\t%lu\t%lu\n", &reg_model->nsample, &reg_model->minx, &reg_model->maxx);
	STARPU_ASSERT_MSG(res == 3, "Incorrect performance model file");

	/* If any of the parameters describing the linear regression model is NaN, the model is invalid */
	unsigned invalid = (isnan(reg_model->alpha)||isnan(reg_model->beta));
	reg_model->valid = !invalid && VALID_REGRESSION(reg_model);

	/*
	 * Non-Linear Regression model
	 */

	_starpu_drop_comments(f);

	res = _starpu_read_double(f, "%le\t", &reg_model->a);
	STARPU_ASSERT_MSG(res == 1, "Incorrect performance model file");
	res = _starpu_read_double(f, "%le\t", &reg_model->b);
	STARPU_ASSERT_MSG(res == 1, "Incorrect performance model file");
	res = _starpu_read_double(f, "%le\n", &reg_model->c);
	STARPU_ASSERT_MSG(res == 1, "Incorrect performance model file");

	/* If any of the parameters describing the non-linear regression model is NaN, the model is invalid */
	unsigned nl_invalid = (isnan(reg_model->a)||isnan(reg_model->b)||isnan(reg_model->c));
	reg_model->nl_valid = !nl_invalid && VALID_REGRESSION(reg_model);
}

static void dump_history_entry(FILE *f, struct starpu_perfmodel_history_entry *entry)
{
	fprintf(f, "%08x\t%-15lu\t%-15le\t%-15le\t%-15le\t%-15le\t%-15le\t%u\n", entry->footprint, (unsigned long) entry->size, entry->flops, entry->mean, entry->deviation, entry->sum, entry->sum2, entry->nsample);
}

static void scan_history_entry(FILE *f, struct starpu_perfmodel_history_entry *entry)
{
	int res;

	_starpu_drop_comments(f);

	/* In case entry is NULL, we just drop these values */
	unsigned nsample;
	uint32_t footprint;
	unsigned long size; /* in bytes */
	double flops;
	double mean;
	double deviation;
	double sum;
	double sum2;

	char line[256];
	char *ret;

	ret = fgets(line, sizeof(line), f);
	STARPU_ASSERT(ret);
	STARPU_ASSERT(strchr(line, '\n'));

	/* Read the values from the file */
	res = sscanf(line, "%x\t%lu\t%le\t%le\t%le\t%le\t%le\t%u", &footprint, &size, &flops, &mean, &deviation, &sum, &sum2, &nsample);

	if (res != 8)
	{
		flops = 0.;
		/* Read the values from the file */
		res = sscanf(line, "%x\t%lu\t%le\t%le\t%le\t%le\t%u", &footprint, &size, &mean, &deviation, &sum, &sum2, &nsample);
		STARPU_ASSERT_MSG(res == 7, "Incorrect performance model file");
	}

	if (entry)
	{
		entry->footprint = footprint;
		entry->size = size;
		entry->flops = flops;
		entry->mean = mean;
		entry->deviation = deviation;
		entry->sum = sum;
		entry->sum2 = sum2;
		entry->nsample = nsample;
	}
}

static void parse_per_arch_model_file(FILE *f, struct starpu_perfmodel_per_arch *per_arch_model, unsigned scan_history)
{
	unsigned nentries;

	_starpu_drop_comments(f);

	int res = fscanf(f, "%u\n", &nentries);
	STARPU_ASSERT_MSG(res == 1, "Incorrect performance model file");

	scan_reg_model(f, &per_arch_model->regression);

	/* parse entries */
	unsigned i;
	for (i = 0; i < nentries; i++)
	{
		struct starpu_perfmodel_history_entry *entry = NULL;
		if (scan_history)
		{
			entry = (struct starpu_perfmodel_history_entry *) malloc(sizeof(struct starpu_perfmodel_history_entry));
			STARPU_ASSERT(entry);

			/* Tell  helgrind that we do not care about
			 * racing access to the sampling, we only want a
			 * good-enough estimation */
			STARPU_HG_DISABLE_CHECKING(entry->nsample);
			STARPU_HG_DISABLE_CHECKING(entry->mean);
			entry->nerror = 0;
		}

		scan_history_entry(f, entry);

		/* insert the entry in the hashtable and the list structures  */
		/* TODO: Insert it at the end of the list, to avoid reversing
		 * the order... But efficiently! We may have a lot of entries */
		if (scan_history)
			insert_history_entry(entry, &per_arch_model->list, &per_arch_model->history);
	}
}


static void parse_arch(FILE *f, struct starpu_perfmodel *model, unsigned scan_history,struct starpu_perfmodel_arch* arch)
{
	struct starpu_perfmodel_per_arch dummy;
	unsigned nimpls, implmax, impl, i, ret;
	//_STARPU_DEBUG("Parsing %s_%u_parallel_%u\n",
	//		starpu_perfmodel_get_archtype_name(arch->type),
	//		arch->devid,
	//		arch->ncore + 1);

	/* Parsing number of implementation */
	_starpu_drop_comments(f);
	ret = fscanf(f, "%u\n", &nimpls);
	STARPU_ASSERT_MSG(ret == 1, "Incorrect performance model file");

	if( model != NULL)
	{
		/* Parsing each implementation */
		implmax = STARPU_MIN(nimpls, STARPU_MAXIMPLEMENTATIONS);
		for (impl = 0; impl < implmax; impl++)
			parse_per_arch_model_file(f, &model->per_arch[arch->type][arch->devid][arch->ncore][impl], scan_history);
	}
	else
	{
		impl = 0;
	}

	/* if the number of implementation is greater than STARPU_MAXIMPLEMENTATIONS
	 * we skip the last implementation */
	for (i = impl; i < nimpls; i++)
		parse_per_arch_model_file(f, &dummy, 0);

}

static void parse_device(FILE *f, struct starpu_perfmodel *model, unsigned scan_history, enum starpu_worker_archtype archtype, unsigned devid)
{
	unsigned maxncore, ncore, ret, i;
	struct starpu_perfmodel_arch arch;
	arch.type = archtype;
	arch.devid = devid;
	//_STARPU_DEBUG("Parsing device %s_%u arch\n",
	//		starpu_perfmodel_get_archtype_name(archtype),
	//		devid);

	/* Parsing maximun number of worker for this device */
	_starpu_drop_comments(f);
	ret = fscanf(f, "%u\n", &maxncore);
	STARPU_ASSERT_MSG(ret == 1, "Incorrect performance model file");

	/* Parsing each arch */
	if(model !=NULL)
	{
		for(ncore=0; ncore < maxncore && model->per_arch[archtype][devid][ncore] != NULL; ncore++)
		{
			arch.ncore = ncore;
			parse_arch(f,model,scan_history,&arch);
		}
	}
	else
	{
		ncore=0;
	}

	for(i=ncore; i < maxncore; i++)
	{
		arch.ncore = i;
		parse_arch(f,NULL,scan_history,&arch);
	}
}


static void parse_archtype(FILE *f, struct starpu_perfmodel *model, unsigned scan_history, enum starpu_worker_archtype archtype)
{
	unsigned ndevice, devid, ret, i;
	//_STARPU_DEBUG("Parsing %s arch\n", starpu_perfmodel_get_archtype_name(archtype));

	/* Parsing number of device for this archtype */
	_starpu_drop_comments(f);
	ret = fscanf(f, "%u\n", &ndevice);
	STARPU_ASSERT_MSG(ret == 1, "Incorrect performance model file");

	/* Parsing each device for this archtype*/
	if(model != NULL)
	{
		for(devid=0; devid < ndevice && model->per_arch[archtype][devid] != NULL; devid++)
		{
				parse_device(f,model,scan_history,archtype,devid);
		}
	}
	else
	{
		devid=0;
	}

	for(i=devid; i < ndevice; i++)
	{
		parse_device(f,NULL,scan_history,archtype,i);
	}
}

static void parse_model_file(FILE *f, struct starpu_perfmodel *model, unsigned scan_history)
{
	unsigned archtype;
	int ret, version;

	//_STARPU_DEBUG("Start parsing\n");

	/* Parsing performance model version */
	_starpu_drop_comments(f);
	ret = fscanf(f, "%d\n", &version);
	STARPU_ASSERT_MSG(version == _STARPU_PERFMODEL_VERSION, "Incorrect performance model file with a model version %d not being the current model version (%d)\n",
			  version, _STARPU_PERFMODEL_VERSION);
	STARPU_ASSERT_MSG(ret == 1, "Incorrect performance model file");

	/* Parsing each kind of archtype */
	for(archtype=0; archtype<STARPU_NARCH; archtype++)
	{
		parse_archtype(f, model, scan_history, archtype);
	}
}


static void dump_per_arch_model_file(FILE *f, struct starpu_perfmodel *model, struct starpu_perfmodel_arch * arch, unsigned nimpl)
{
	struct starpu_perfmodel_per_arch *per_arch_model;

	per_arch_model = &model->per_arch[arch->type][arch->devid][arch->ncore][nimpl];
	/* count the number of elements in the lists */
	struct starpu_perfmodel_history_list *ptr = NULL;
	unsigned nentries = 0;

	if (model->type == STARPU_HISTORY_BASED || model->type == STARPU_NL_REGRESSION_BASED)
	{
		/* Dump the list of all entries in the history */
		ptr = per_arch_model->list;
		while(ptr)
		{
			nentries++;
			ptr = ptr->next;
		}
	}

	/* header */
	char archname[32];
	starpu_perfmodel_get_arch_name(arch, archname, 32, nimpl);
	fprintf(f, "#####\n");
	fprintf(f, "# Model for %s\n", archname);
	fprintf(f, "# number of entries\n%u\n", nentries);

	dump_reg_model(f, model, arch, nimpl);

	/* Dump the history into the model file in case it is necessary */
	if (model->type == STARPU_HISTORY_BASED || model->type == STARPU_NL_REGRESSION_BASED)
	{
		fprintf(f, "# hash\t\tsize\t\tflops\t\tmean (us)\tdev (us)\tsum\t\tsum2\t\tn\n");
		ptr = per_arch_model->list;
		while (ptr)
		{
			dump_history_entry(f, ptr->entry);
			ptr = ptr->next;
		}
	}

	fprintf(f, "\n");
}

static unsigned get_n_entries(struct starpu_perfmodel *model, struct starpu_perfmodel_arch * arch, unsigned impl)
{
	struct starpu_perfmodel_per_arch *per_arch_model;
	per_arch_model = &model->per_arch[arch->type][arch->devid][arch->ncore][impl];
	/* count the number of elements in the lists */
	struct starpu_perfmodel_history_list *ptr = NULL;
	unsigned nentries = 0;

	if (model->type == STARPU_HISTORY_BASED || model->type == STARPU_NL_REGRESSION_BASED)
	{
		/* Dump the list of all entries in the history */
		ptr = per_arch_model->list;
		while(ptr)
		{
			nentries++;
			ptr = ptr->next;
		}
	}
	return nentries;
}

static void dump_model_file(FILE *f, struct starpu_perfmodel *model)
{
	struct _starpu_machine_config *conf = _starpu_get_machine_config();
	char *name = "unknown";
	unsigned archtype, ndevice, *ncore, devid, nc, nimpl;
	struct starpu_perfmodel_arch arch;

	fprintf(f, "##################\n");
	fprintf(f, "# Performance Model Version\n");
	fprintf(f, "%d\n\n", _STARPU_PERFMODEL_VERSION);

	for(archtype=0; archtype<STARPU_NARCH; archtype++)
	{
		arch.type = archtype;
		switch (archtype)
		{
			case STARPU_CPU_WORKER:
				ndevice = 1;
				ncore = &conf->topology.nhwcpus;
				name = "CPU";
				break;
			case STARPU_CUDA_WORKER:
				ndevice = conf->topology.nhwcudagpus;
				ncore = NULL;
				name = "CUDA";
				break;
			case STARPU_OPENCL_WORKER:
				ndevice = conf->topology.nhwopenclgpus;
				ncore = NULL;
				name = "OPENCL";
				break;
			case STARPU_MIC_WORKER:
				ndevice = conf->topology.nhwmicdevices;
				ncore = conf->topology.nhwmiccores;
				name = "MIC";
				break;
			case STARPU_SCC_WORKER:
				ndevice = conf->topology.nhwscc;
				ncore = NULL;
				name = "SCC";
				break;
			default:
				/* Unknown arch */
				STARPU_ABORT();
				break;
		}

		fprintf(f, "####################\n");
		fprintf(f, "# %ss\n", name);
		fprintf(f, "# number of %s devices\n", name);
		fprintf(f, "%u\n", ndevice);


		for(devid=0; devid<ndevice; devid++)
		{
			arch.devid = devid;
			fprintf(f, "###############\n");
			fprintf(f, "# %s_%u\n", name, devid);
			fprintf(f, "# number of workers on device %s_%d\n", name, devid);
			if(ncore != NULL)
				fprintf(f, "%u\n", ncore[devid]);
			else
				fprintf(f, "1\n");
			for(nc=0; model->per_arch[archtype][devid][nc] != NULL; nc++)
			{

				arch.ncore = nc;
				unsigned max_impl = 0;
				if (model->type == STARPU_HISTORY_BASED || model->type == STARPU_NL_REGRESSION_BASED)
				{
					for (nimpl = 0; nimpl < STARPU_MAXIMPLEMENTATIONS; nimpl++)
						if (get_n_entries(model, &arch, nimpl))
							max_impl = nimpl + 1;
				}
				else if (model->type == STARPU_REGRESSION_BASED || model->type == STARPU_PER_ARCH || model->type == STARPU_COMMON)
				{
					for (nimpl = 0; nimpl < STARPU_MAXIMPLEMENTATIONS; nimpl++)
						if (model->per_arch[archtype][devid][nc][nimpl].regression.nsample)
							max_impl = nimpl + 1;
				}
				else
					STARPU_ASSERT_MSG(0, "Unknown history-based performance model %u", model->type);

				fprintf(f, "##########\n");
				fprintf(f, "# %u worker(s) in parallel\n", nc+1);

				fprintf(f, "# number of implementations\n");
				fprintf(f, "%u\n", max_impl);
				for (nimpl = 0; nimpl < max_impl; nimpl++)
				{
					dump_per_arch_model_file(f, model, &arch, nimpl);
				}
			}
		}
	}
}

static void initialize_per_arch_model(struct starpu_perfmodel_per_arch *per_arch_model)
{
	memset(per_arch_model, 0, sizeof(struct starpu_perfmodel_per_arch));
}

static struct starpu_perfmodel_per_arch*** initialize_arch_model(int maxdevid, unsigned* maxncore_table)
{
	int devid, ncore, nimpl;
	struct starpu_perfmodel_per_arch *** arch_model = malloc(sizeof(*arch_model)*(maxdevid+1));
	arch_model[maxdevid] = NULL;
	for(devid=0; devid<maxdevid; devid++)
	{
		int maxncore;
		if(maxncore_table != NULL)
			maxncore = maxncore_table[devid];
		else
			maxncore = 1;

		arch_model[devid] = malloc(sizeof(*arch_model[devid])*(maxncore+1));
		arch_model[devid][maxncore] = NULL;
		for(ncore=0; ncore<maxncore; ncore++)
		{
			arch_model[devid][ncore] = malloc(sizeof(*arch_model[devid][ncore])*STARPU_MAXIMPLEMENTATIONS);
			for(nimpl=0; nimpl<STARPU_MAXIMPLEMENTATIONS; nimpl++)
			{
				initialize_per_arch_model(&arch_model[devid][ncore][nimpl]);
			}
		}
	}
	return arch_model;
}

static void initialize_model(struct starpu_perfmodel *model)
{
	struct _starpu_machine_config *conf = _starpu_get_machine_config();
	model->per_arch = malloc(sizeof(*model->per_arch)*(STARPU_NARCH));

	model->per_arch[STARPU_CPU_WORKER] = initialize_arch_model(1,&conf->topology.nhwcpus);
	model->per_arch[STARPU_CUDA_WORKER] = initialize_arch_model(conf->topology.nhwcudagpus,NULL);
	model->per_arch[STARPU_OPENCL_WORKER] = initialize_arch_model(conf->topology.nhwopenclgpus,NULL);
	model->per_arch[STARPU_MIC_WORKER] = initialize_arch_model(conf->topology.nhwmicdevices,conf->topology.nhwmiccores);
	model->per_arch[STARPU_SCC_WORKER] = initialize_arch_model(conf->topology.nhwscc,NULL);
}

static void initialize_model_with_file(FILE*f, struct starpu_perfmodel *model)
{
	unsigned ret, archtype, devid, i, ndevice, * maxncore;
	struct starpu_perfmodel_arch arch;
	int version;

	/* Parsing performance model version */
	_starpu_drop_comments(f);
	ret = fscanf(f, "%d\n", &version);
	STARPU_ASSERT_MSG(version == _STARPU_PERFMODEL_VERSION, "Incorrect performance model file with a model version %d not being the current model version (%d)\n",
			version, _STARPU_PERFMODEL_VERSION);
	STARPU_ASSERT_MSG(ret == 1, "Incorrect performance model file");

	model->per_arch = malloc(sizeof(*model->per_arch)*(STARPU_NARCH));
	for(archtype=0; archtype<STARPU_NARCH; archtype++)
	{
		arch.type = archtype;

		_starpu_drop_comments(f);
		ret = fscanf(f, "%u\n", &ndevice);
		STARPU_ASSERT_MSG(ret == 1, "Incorrect performance model file");

		if(ndevice != 0)
			maxncore = malloc(sizeof(*maxncore)*ndevice);
		else
			maxncore = NULL;

		for(devid=0; devid < ndevice; devid++)
		{
			arch.devid = devid;

			_starpu_drop_comments(f);
			ret = fscanf(f, "%u\n", &maxncore[devid]);
			STARPU_ASSERT_MSG(ret == 1, "Incorrect performance model file");

			for(i=0; i<maxncore[devid]; i++)
			{
				arch.ncore = i;

				parse_arch(f,NULL,0,&arch);
			}
		}

		model->per_arch[archtype] = initialize_arch_model(ndevice,maxncore);
		if(maxncore != NULL)
			free(maxncore);
	}
}

void starpu_perfmodel_init(struct starpu_perfmodel *model)
{
	STARPU_ASSERT(model && model->symbol);

	int already_init;

	STARPU_PTHREAD_RWLOCK_RDLOCK(&registered_models_rwlock);
	already_init = model->is_init;
	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);

	if (already_init)
		return;

	/* The model is still not loaded so we grab the lock in write mode, and
	 * if it's not loaded once we have the lock, we do load it. */
	STARPU_PTHREAD_RWLOCK_WRLOCK(&registered_models_rwlock);

	/* Was the model initialized since the previous test ? */
	if (model->is_init)
	{
		STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
		return;
	}

	STARPU_PTHREAD_RWLOCK_INIT(&model->model_rwlock, NULL);
	if(model->type != STARPU_COMMON)
		initialize_model(model);
	model->is_init = 1;
	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
}

void starpu_perfmodel_init_with_file(FILE*f, struct starpu_perfmodel *model)
{
	STARPU_ASSERT(model && model->symbol);

	int already_init;

	STARPU_PTHREAD_RWLOCK_RDLOCK(&registered_models_rwlock);
	already_init = model->is_init;
	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);

	if (already_init)
		return;

	/* The model is still not loaded so we grab the lock in write mode, and
	 * if it's not loaded once we have the lock, we do load it. */
	STARPU_PTHREAD_RWLOCK_WRLOCK(&registered_models_rwlock);

	/* Was the model initialized since the previous test ? */
	if (model->is_init)
	{
		STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
		return;
	}

	STARPU_PTHREAD_RWLOCK_INIT(&model->model_rwlock, NULL);
	if(model->type != STARPU_COMMON)
		initialize_model_with_file(f,model);
	model->is_init = 1;
	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
}


static void get_model_debug_path(struct starpu_perfmodel *model, const char *arch, char *path, size_t maxlen)
{
	STARPU_ASSERT(path);

	_starpu_get_perf_model_dir_debug(path, maxlen);
	strncat(path, model->symbol, maxlen);

	char hostname[65];
	_starpu_gethostname(hostname, sizeof(hostname));
	strncat(path, ".", maxlen);
	strncat(path, hostname, maxlen);
	strncat(path, ".", maxlen);
	strncat(path, arch, maxlen);
	strncat(path, ".debug", maxlen);
}

/*
 * Returns 0 is the model was already loaded, 1 otherwise.
 */
int _starpu_register_model(struct starpu_perfmodel *model)
{
	starpu_perfmodel_init(model);

	/* If the model has already been loaded, there is nothing to do */
	STARPU_PTHREAD_RWLOCK_RDLOCK(&registered_models_rwlock);
	if (model->is_loaded)
	{
		STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
		return 0;
	}
	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);

	/* We have to make sure the model has not been loaded since the
         * last time we took the lock */
	STARPU_PTHREAD_RWLOCK_WRLOCK(&registered_models_rwlock);
	if (model->is_loaded)
	{
		STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
		return 0;
	}

	/* add the model to a linked list */
	struct _starpu_perfmodel_list *node = (struct _starpu_perfmodel_list *) malloc(sizeof(struct _starpu_perfmodel_list));

	node->model = model;
	//model->debug_modelid = debug_modelid++;

	/* put this model at the beginning of the list */
	node->next = registered_models;
	registered_models = node;

#ifdef STARPU_MODEL_DEBUG
	_starpu_create_sampling_directory_if_needed();

	unsigned archtype, devid, ncore, nimpl;
	struct starpu_perfmodel_arch arch;

	_STARPU_DEBUG("\n\n ###\nHere\n ###\n\n");

	if(model->is_init)
	{
		_STARPU_DEBUG("Init\n");
		for (archtype = 0; archtype < STARPU_NARCH; archtype++)
		{
			_STARPU_DEBUG("Archtype\n");
			arch.type = archtype;
			if(model->per_arch[archtype] != NULL)
			{
				for(devid=0; model->per_arch[archtype][devid] != NULL; devid++)
				{
					_STARPU_DEBUG("Devid\n");
					arch.devid = devid;
					for(ncore=0; model->per_arch[archtype][devid][ncore] != NULL; ncore++)
					{
						_STARPU_DEBUG("Ncore\n");
						arch.ncore = ncore;
						for (nimpl = 0; nimpl < STARPU_MAXIMPLEMENTATIONS; nimpl++)
						{
							starpu_perfmodel_debugfilepath(model, &arch, model->per_arch[archtype][devid][ncore][nimpl].debug_path, 256, nimpl);
						}
					}
				}
			}
		}
	}
#endif

	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
	return 1;
}

static void get_model_path(struct starpu_perfmodel *model, char *path, size_t maxlen)
{
	_starpu_get_perf_model_dir_codelets(path, maxlen);
	strncat(path, model->symbol, maxlen);

	char hostname[65];
	_starpu_gethostname(hostname, sizeof(hostname));
	strncat(path, ".", maxlen);
	strncat(path, hostname, maxlen);
}

static void save_history_based_model(struct starpu_perfmodel *model)
{
	STARPU_ASSERT(model);
	STARPU_ASSERT(model->symbol);

	/* TODO checks */

	/* filename = $STARPU_PERF_MODEL_DIR/codelets/symbol.hostname */
	char path[256];
	get_model_path(model, path, 256);

	_STARPU_DEBUG("Opening performance model file %s for model %s\n", path, model->symbol);

	/* overwrite existing file, or create it */
	FILE *f;
	f = fopen(path, "w+");
	STARPU_ASSERT_MSG(f, "Could not save performance model %s\n", path);

	dump_model_file(f, model);

	fclose(f);
}

static void _starpu_dump_registered_models(void)
{
#ifndef STARPU_SIMGRID
	STARPU_PTHREAD_RWLOCK_WRLOCK(&registered_models_rwlock);

	struct _starpu_perfmodel_list *node;
	node = registered_models;

	_STARPU_DEBUG("DUMP MODELS !\n");

	while (node)
	{
		save_history_based_model(node->model);
		node = node->next;
	}

	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
#endif
}

void _starpu_initialize_registered_performance_models(void)
{
	registered_models = NULL;

	STARPU_PTHREAD_RWLOCK_INIT(&registered_models_rwlock, NULL);
}

void _starpu_deinitialize_performance_model(struct starpu_perfmodel *model)
{
	unsigned arch, devid, ncore, nimpl;

	if(model->is_init && model->per_arch != NULL)
	{
		for (arch = 0; arch < STARPU_NARCH; arch++)
		{
			if( model->per_arch[arch] != NULL)
			{
				for(devid=0; model->per_arch[arch][devid] != NULL; devid++)
				{
					for(ncore=0; model->per_arch[arch][devid][ncore] != NULL; ncore++)
					{
						for (nimpl = 0; nimpl < STARPU_MAXIMPLEMENTATIONS; nimpl++)
						{
							struct starpu_perfmodel_per_arch *archmodel = &model->per_arch[arch][devid][ncore][nimpl];
							struct starpu_perfmodel_history_list *list, *plist;
							struct starpu_perfmodel_history_table *entry, *tmp;

							HASH_ITER(hh, archmodel->history, entry, tmp)
							{
								HASH_DEL(archmodel->history, entry);
								free(entry);
							}
							archmodel->history = NULL;

							list = archmodel->list;
							while (list)
							{
								free(list->entry);
								plist = list;
								list = list->next;
								free(plist);
							}
							archmodel->list = NULL;
						}
						free(model->per_arch[arch][devid][ncore]);
						model->per_arch[arch][devid][ncore] = NULL;
					}
					free(model->per_arch[arch][devid]);
					model->per_arch[arch][devid] = NULL;
				}
				free(model->per_arch[arch]);
				model->per_arch[arch] = NULL;
			}
		}
		free(model->per_arch);
		model->per_arch = NULL;
	}

	model->is_init = 0;
	model->is_loaded = 0;
}

void _starpu_deinitialize_registered_performance_models(void)
{
	if (_starpu_get_calibrate_flag())
		_starpu_dump_registered_models();

	STARPU_PTHREAD_RWLOCK_WRLOCK(&registered_models_rwlock);

	struct _starpu_perfmodel_list *node, *pnode;
	node = registered_models;

	_STARPU_DEBUG("FREE MODELS !\n");

	while (node)
	{
		struct starpu_perfmodel *model = node->model;

		STARPU_PTHREAD_RWLOCK_WRLOCK(&model->model_rwlock);
		_starpu_deinitialize_performance_model(model);
		STARPU_PTHREAD_RWLOCK_UNLOCK(&model->model_rwlock);

		pnode = node;
		node = node->next;
		free(pnode);
	}
	registered_models = NULL;

	STARPU_PTHREAD_RWLOCK_UNLOCK(&registered_models_rwlock);
	STARPU_PTHREAD_RWLOCK_DESTROY(&registered_models_rwlock);
}

/*
 * XXX: We should probably factorize the beginning of the _starpu_load_*_model
 * functions. This is a bit tricky though, because we must be sure to unlock
 * registered_models_rwlock at the right place.
 */
void _starpu_load_per_arch_based_model(struct starpu_perfmodel *model)
{
	starpu_perfmodel_init(model);
}

void _starpu_load_common_based_model(struct starpu_perfmodel *model)
{
	starpu_perfmodel_init(model);
}

/* We first try to grab the global lock in read mode to check whether the model
 * was loaded or not (this is very likely to have been already loaded). If the
 * model was not loaded yet, we take the lock in write mode, and if the model
 * is still not loaded once we have the lock, we do load it.  */
void _starpu_load_history_based_model(struct starpu_perfmodel *model, unsigned scan_history)
{
	starpu_perfmodel_init(model);

	STARPU_PTHREAD_RWLOCK_WRLOCK(&model->model_rwlock);

	if(!model->is_loaded)
	{
		/* make sure the performance model directory exists (or create it) */
		_starpu_create_sampling_directory_if_needed();

		char path[256];
		get_model_path(model, path, 256);

		_STARPU_DEBUG("Opening performance model file %s for model %s ...\n", path, model->symbol);

		unsigned calibrate_flag = _starpu_get_calibrate_flag();
		model->benchmarking = calibrate_flag;

		/* try to open an existing file and load it */
		int res;
		res = access(path, F_OK);
		if (res == 0)
		{
			if (calibrate_flag == 2)
			{
				/* The user specified that the performance model should
				 * be overwritten, so we don't load the existing file !
				 * */
				_STARPU_DEBUG("Overwrite existing file\n");
			}
			else
			{
				/* We load the available file */
				_STARPU_DEBUG("File exists\n");
				FILE *f;
				f = fopen(path, "r");
				STARPU_ASSERT(f);

				parse_model_file(f, model, scan_history);

				fclose(f);
			}
		}
		else
		{
			_STARPU_DEBUG("File does not exists\n");
		}

		_STARPU_DEBUG("Performance model file %s for model %s is loaded\n", path, model->symbol);

		model->is_loaded = 1;
	}
	STARPU_PTHREAD_RWLOCK_UNLOCK(&model->model_rwlock);

}

void starpu_perfmodel_directory(FILE *output)
{
	char perf_model_dir[256];
	_starpu_get_perf_model_dir_codelets(perf_model_dir, 256);
	fprintf(output, "directory: <%s>\n", perf_model_dir);
}

/* This function is intended to be used by external tools that should read
 * the performance model files */
int starpu_perfmodel_list(FILE *output)
{
        char path[256];
        DIR *dp;
        struct dirent *ep;

	char perf_model_dir_codelets[256];
	_starpu_get_perf_model_dir_codelets(perf_model_dir_codelets, 256);

        strncpy(path, perf_model_dir_codelets, 256);
        dp = opendir(path);
        if (dp != NULL)
	{
                while ((ep = readdir(dp)))
		{
                        if (strcmp(ep->d_name, ".") && strcmp(ep->d_name, ".."))
                                fprintf(output, "file: <%s>\n", ep->d_name);
                }
                closedir (dp);
        }
        else
	{
		_STARPU_DISP("Could not open the perfmodel directory <%s>: %s\n", path, strerror(errno));
        }
	return 0;
}

/* This function is intended to be used by external tools that should read the
 * performance model files */
/* TODO: write an clear function, to free symbol and history */
int starpu_perfmodel_load_symbol(const char *symbol, struct starpu_perfmodel *model)
{
	model->symbol = strdup(symbol);

	/* where is the file if it exists ? */
	char path[256];
	get_model_path(model, path, 256);

	//	_STARPU_DEBUG("get_model_path -> %s\n", path);

	/* does it exist ? */
	int res;
	res = access(path, F_OK);
	if (res)
	{
		const char *dot = strrchr(symbol, '.');
		if (dot)
		{
			char *symbol2 = strdup(symbol);
			symbol2[dot-symbol] = '\0';
			int ret;
			_STARPU_DISP("note: loading history from %s instead of %s\n", symbol2, symbol);
			ret = starpu_perfmodel_load_symbol(symbol2,model);
			free(symbol2);
			return ret;
		}
		_STARPU_DISP("There is no performance model for symbol %s\n", symbol);
		return 1;
	}

	FILE *f = fopen(path, "r");
	STARPU_ASSERT(f);

	starpu_perfmodel_init_with_file(f, model);
	rewind(f);

	parse_model_file(f, model, 1);

	STARPU_ASSERT(fclose(f) == 0);

	return 0;
}

int starpu_perfmodel_unload_model(struct starpu_perfmodel *model)
{
	free((char *)model->symbol);
	_starpu_deinitialize_performance_model(model);
	return 0;
}

char* starpu_perfmodel_get_archtype_name(enum starpu_worker_archtype archtype)
{
	switch(archtype)
	{
		case(STARPU_CPU_WORKER):
			return "cpu";
			break;
		case(STARPU_CUDA_WORKER):
			return "cuda";
			break;
		case(STARPU_OPENCL_WORKER):
			return "opencl";
			break;
		case(STARPU_MIC_WORKER):
			return "mic";
			break;
		case(STARPU_SCC_WORKER):
			return "scc";
			break;
		default:
			STARPU_ABORT();
			break;
	}
}

void starpu_perfmodel_get_arch_name(struct starpu_perfmodel_arch* arch, char *archname, size_t maxlen,unsigned nimpl)
{
	snprintf(archname, maxlen, "%s%d_parallel%d_impl%u",
			starpu_perfmodel_get_archtype_name(arch->type),
			arch->devid,
			arch->ncore + 1,
			nimpl);
}

void starpu_perfmodel_debugfilepath(struct starpu_perfmodel *model,
				    struct starpu_perfmodel_arch* arch, char *path, size_t maxlen, unsigned nimpl)
{
	char archname[32];
	starpu_perfmodel_get_arch_name(arch, archname, 32, nimpl);

	STARPU_ASSERT(path);

	get_model_debug_path(model, archname, path, maxlen);
}

double _starpu_regression_based_job_expected_perf(struct starpu_perfmodel *model, struct starpu_perfmodel_arch* arch, struct _starpu_job *j, unsigned nimpl)
{
	double exp = NAN;
	size_t size = _starpu_job_get_data_size(model, arch, nimpl, j);
	struct starpu_perfmodel_regression_model *regmodel;

	regmodel = &model->per_arch[arch->type][arch->devid][arch->ncore][nimpl].regression;

	if (regmodel->valid && size >= regmodel->minx * 0.9 && size <= regmodel->maxx * 1.1)
                exp = regmodel->alpha*pow((double)size, regmodel->beta);

	return exp;
}

double _starpu_non_linear_regression_based_job_expected_perf(struct starpu_perfmodel *model, struct starpu_perfmodel_arch* arch, struct _starpu_job *j,unsigned nimpl)
{
	double exp = NAN;
	size_t size = _starpu_job_get_data_size(model, arch, nimpl, j);
	struct starpu_perfmodel_regression_model *regmodel;

	regmodel = &model->per_arch[arch->type][arch->devid][arch->ncore][nimpl].regression;

	if (regmodel->nl_valid && size >= regmodel->minx * 0.9 && size <= regmodel->maxx * 1.1)
		exp = regmodel->a*pow((double)size, regmodel->b) + regmodel->c;
	else
	{
		uint32_t key = _starpu_compute_buffers_footprint(model, arch, nimpl, j);
		struct starpu_perfmodel_per_arch *per_arch_model = &model->per_arch[arch->type][arch->devid][arch->ncore][nimpl];
		struct starpu_perfmodel_history_table *history;
		struct starpu_perfmodel_history_table *entry;

		STARPU_PTHREAD_RWLOCK_RDLOCK(&model->model_rwlock);
		history = per_arch_model->history;
		HASH_FIND_UINT32_T(history, &key, entry);
		STARPU_PTHREAD_RWLOCK_UNLOCK(&model->model_rwlock);

		/* Here helgrind would shout that this is unprotected access.
		 * We do not care about racing access to the mean, we only want
		 * a good-enough estimation */

		if (entry && entry->history_entry && entry->history_entry->nsample >= _STARPU_CALIBRATION_MINIMUM)
			exp = entry->history_entry->mean;

		STARPU_HG_DISABLE_CHECKING(model->benchmarking);
		if (isnan(exp) && !model->benchmarking)
		{
			char archname[32];

			starpu_perfmodel_get_arch_name(arch, archname, sizeof(archname), nimpl);
			_STARPU_DISP("Warning: model %s is not calibrated enough for %s, forcing calibration for this run. Use the STARPU_CALIBRATE environment variable to control this.\n", model->symbol, archname);
			_starpu_set_calibrate_flag(1);
			model->benchmarking = 1;
		}
	}

	return exp;
}

double _starpu_history_based_job_expected_perf(struct starpu_perfmodel *model, struct starpu_perfmodel_arch* arch, struct _starpu_job *j,unsigned nimpl)
{
	double exp = NAN;
	struct starpu_perfmodel_per_arch *per_arch_model;
	struct starpu_perfmodel_history_entry *entry;
	struct starpu_perfmodel_history_table *history, *elt;

	uint32_t key = _starpu_compute_buffers_footprint(model, arch, nimpl, j);

	per_arch_model = &model->per_arch[arch->type][arch->devid][arch->ncore][nimpl];

	STARPU_PTHREAD_RWLOCK_RDLOCK(&model->model_rwlock);
	history = per_arch_model->history;
	HASH_FIND_UINT32_T(history, &key, elt);
	entry = (elt == NULL) ? NULL : elt->history_entry;
	STARPU_PTHREAD_RWLOCK_UNLOCK(&model->model_rwlock);

	/* Here helgrind would shout that this is unprotected access.
	 * We do not care about racing access to the mean, we only want
	 * a good-enough estimation */

	if (entry && entry->nsample >= _STARPU_CALIBRATION_MINIMUM)
		/* TODO: report differently if we've scheduled really enough
		 * of that task and the scheduler should perhaps put it aside */
		/* Calibrated enough */
		exp = entry->mean;

	STARPU_HG_DISABLE_CHECKING(model->benchmarking);
	if (isnan(exp) && !model->benchmarking)
	{
		char archname[32];

		starpu_perfmodel_get_arch_name(arch, archname, sizeof(archname), nimpl);
		_STARPU_DISP("Warning: model %s is not calibrated enough for %s, forcing calibration for this run. Use the STARPU_CALIBRATE environment variable to control this.\n", model->symbol, archname);
		_starpu_set_calibrate_flag(1);
		model->benchmarking = 1;
	}

	return exp;
}

double starpu_permodel_history_based_expected_perf(struct starpu_perfmodel *model, struct starpu_perfmodel_arch * arch, uint32_t footprint)
{
	struct _starpu_job j =
		{
			.footprint = footprint,
			.footprint_is_computed = 1,
		};
	return _starpu_history_based_job_expected_perf(model, arch, &j, j.nimpl);
}

void _starpu_update_perfmodel_history(struct _starpu_job *j, struct starpu_perfmodel *model, struct starpu_perfmodel_arch* arch, unsigned cpuid STARPU_ATTRIBUTE_UNUSED, double measured, unsigned nimpl)
{
	if (model)
	{
		STARPU_PTHREAD_RWLOCK_WRLOCK(&model->model_rwlock);

		struct starpu_perfmodel_per_arch *per_arch_model = &model->per_arch[arch->type][arch->devid][arch->ncore][nimpl];

		if (model->type == STARPU_HISTORY_BASED || model->type == STARPU_NL_REGRESSION_BASED)
		{
			struct starpu_perfmodel_history_entry *entry;
			struct starpu_perfmodel_history_table *elt;
			struct starpu_perfmodel_history_list **list;
			uint32_t key = _starpu_compute_buffers_footprint(model, arch, nimpl, j);

			list = &per_arch_model->list;

			HASH_FIND_UINT32_T(per_arch_model->history, &key, elt);
			entry = (elt == NULL) ? NULL : elt->history_entry;

			if (!entry)
			{
				/* this is the first entry with such a footprint */
				entry = (struct starpu_perfmodel_history_entry *) malloc(sizeof(struct starpu_perfmodel_history_entry));
				STARPU_ASSERT(entry);

				/* Tell  helgrind that we do not care about
				 * racing access to the sampling, we only want a
				 * good-enough estimation */
				STARPU_HG_DISABLE_CHECKING(entry->nsample);
				STARPU_HG_DISABLE_CHECKING(entry->mean);

				entry->mean = measured;
				entry->sum = measured;

				entry->deviation = 0.0;
				entry->sum2 = measured*measured;

				entry->size = _starpu_job_get_data_size(model, arch, nimpl, j);
				entry->flops = j->task->flops;

				entry->footprint = key;
				entry->nsample = 1;
				entry->nerror = 0;

				insert_history_entry(entry, list, &per_arch_model->history);
			}
			else
			{
				/* There is already an entry with the same footprint */

				double local_deviation = measured/entry->mean;
				int historymaxerror = starpu_get_env_number_default("STARPU_HISTORY_MAX_ERROR", STARPU_HISTORYMAXERROR);
				
				if (entry->nsample &&
					(100 * local_deviation > (100 + historymaxerror)
					 || (100 / local_deviation > (100 + historymaxerror))))
				{
					entry->nerror++;

					/* More errors than measurements, we're most probably completely wrong, we flush out all the entries */
					if (entry->nerror >= entry->nsample)
					{
						char archname[32];
						starpu_perfmodel_get_arch_name(arch, archname, sizeof(archname), nimpl);
						_STARPU_DISP("Too big deviation for model %s on %s: %f vs average %f, %u such errors against %u samples (%+f%%), flushing the performance model. Use the STARPU_HISTORY_MAX_ERROR environement variable to control the threshold (currently %d%%)\n", model->symbol, archname, measured, entry->mean, entry->nerror, entry->nsample, measured * 100. / entry->mean - 100, historymaxerror);
						entry->sum = 0.0;
						entry->sum2 = 0.0;
						entry->nsample = 0;
						entry->nerror = 0;
						entry->mean = 0.0;
						entry->deviation = 0.0;
					}
				}
				else
				{
					entry->sum += measured;
					entry->sum2 += measured*measured;
					entry->nsample++;

					unsigned n = entry->nsample;
					entry->mean = entry->sum / n;
					entry->deviation = sqrt((entry->sum2 - (entry->sum*entry->sum)/n)/n);
				}

				if (j->task->flops != 0.)
				{
					if (entry->flops == 0.)
						entry->flops = j->task->flops;
					else if (entry->flops != j->task->flops)
						/* Incoherent flops! forget about trying to record flops */
						entry->flops = NAN;
				}
			}

			STARPU_ASSERT(entry);
		}

		if (model->type == STARPU_REGRESSION_BASED || model->type == STARPU_NL_REGRESSION_BASED)
		{
			struct starpu_perfmodel_regression_model *reg_model;
			reg_model = &per_arch_model->regression;

			/* update the regression model */
			size_t job_size = _starpu_job_get_data_size(model, arch, nimpl, j);
			double logy, logx;
			logx = log((double)job_size);
			logy = log(measured);

			reg_model->sumlnx += logx;
			reg_model->sumlnx2 += logx*logx;
			reg_model->sumlny += logy;
			reg_model->sumlnxlny += logx*logy;
			if (reg_model->minx == 0 || job_size < reg_model->minx)
				reg_model->minx = job_size;
			if (reg_model->maxx == 0 || job_size > reg_model->maxx)
				reg_model->maxx = job_size;
			reg_model->nsample++;

			if (VALID_REGRESSION(reg_model))
			{
				unsigned n = reg_model->nsample;

				double num = (n*reg_model->sumlnxlny - reg_model->sumlnx*reg_model->sumlny);
				double denom = (n*reg_model->sumlnx2 - reg_model->sumlnx*reg_model->sumlnx);

				reg_model->beta = num/denom;
				reg_model->alpha = exp((reg_model->sumlny - reg_model->beta*reg_model->sumlnx)/n);
				reg_model->valid = 1;
			}
		}

#ifdef STARPU_MODEL_DEBUG
		struct starpu_task *task = j->task;
		FILE *f = fopen(per_arch_model->debug_path, "a+");
		if (f == NULL)
		{
			_STARPU_DISP("Error <%s> when opening file <%s>\n", strerror(errno), per_arch_model->debug_path);
			STARPU_ABORT();
		}

		if (!j->footprint_is_computed)
			(void) _starpu_compute_buffers_footprint(model, arch, nimpl, j);

		STARPU_ASSERT(j->footprint_is_computed);

		fprintf(f, "0x%x\t%lu\t%f\t%f\t%f\t%d\t\t", j->footprint, (unsigned long) _starpu_job_get_data_size(model, arch, nimpl, j), measured, task->predicted, task->predicted_transfer, cpuid);
		unsigned i;

		for (i = 0; i < task->cl->nbuffers; i++)
		{
			starpu_data_handle_t handle = STARPU_TASK_GET_HANDLE(task, i);

			STARPU_ASSERT(handle->ops);
			STARPU_ASSERT(handle->ops->display);
			handle->ops->display(handle, f);
		}
		fprintf(f, "\n");
		fclose(f);
#endif
		STARPU_PTHREAD_RWLOCK_UNLOCK(&model->model_rwlock);
	}
}

void starpu_perfmodel_update_history(struct starpu_perfmodel *model, struct starpu_task *task, struct starpu_perfmodel_arch * arch, unsigned cpuid, unsigned nimpl, double measured)
{
	struct _starpu_job *job = _starpu_get_job_associated_to_task(task);

#ifdef STARPU_SIMGRID
	STARPU_ASSERT_MSG(0, "We are not supposed to update history when simulating execution");
#endif

	_starpu_load_perfmodel(model);
	/* Record measurement */
	_starpu_update_perfmodel_history(job, model, arch, cpuid, measured, nimpl);
	/* and save perfmodel on termination */
	_starpu_set_calibrate_flag(1);
}