new flag STARPU_EXECUTE_ON_WORKER to specify the worker which will execute the task (thanks to Xavier Lacoste for providing the patch)

ChangeLog

@@ -1,7 +1,7 @@
 # StarPU --- Runtime system for heterogeneous multicore architectures.
 #
 # Copyright (C) 2009-2013  Université de Bordeaux 1
-# Copyright (C) 2010, 2011, 2012, 2013  Centre National de la Recherche Scientifique
+# Copyright (C) 2010, 2011, 2012, 2013, 2014  Centre National de la Recherche Scientifique
 #
 # 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
@@ -61,6 +61,8 @@ Small features:
     history-based calibrator.
   * Tasks can now have a name (via the field const char *name of
     struct starpu_task)
+  * New STARPU_EXECUTE_ON_WORKER flag to specify the worker on which
+    to execute the task.
 
 Changes:
   * Fix of the livelock issue discovered while executing applications

doc/doxygen/chapters/api/insert_task.doxy

@@ -1,7 +1,7 @@
 /*
  * This file is part of the StarPU Handbook.
  * Copyright (C) 2009--2011  Universit@'e de Bordeaux 1
- * Copyright (C) 2010, 2011, 2012, 2013  Centre National de la Recherche Scientifique
+ * Copyright (C) 2010, 2011, 2012, 2013, 2014  Centre National de la Recherche Scientifique
  * Copyright (C) 2011, 2012 Institut National de Recherche en Informatique et Automatique
  * See the file version.doxy for copying conditions.
  */
@@ -23,6 +23,9 @@ The arguments following the codelet can be of the following types:
 ::STARPU_REDUX an access mode followed by a data handle;
 <li> ::STARPU_DATA_ARRAY followed by an array of data handles and its
 number of elements;
+<li> ::STARPU_EXECUTE_ON_WORKER followed by an integer value
+specifying the worker on which to execute the task (as specified by
+starpu_task::execute_on_a_specific_worker)
 <li> the specific values ::STARPU_VALUE, ::STARPU_CALLBACK,
 ::STARPU_CALLBACK_ARG, ::STARPU_CALLBACK_WITH_ARG, ::STARPU_PRIORITY,
 ::STARPU_TAG, ::STARPU_FLOPS, ::STARPU_SCHED_CTX followed by the
@@ -71,6 +74,12 @@ be followed by a integer defining a priority level
 \ingroup API_Insert_Task
 TODO
 
+\def STARPU_EXECUTE_ON_WORKER
+\ingroup API_Insert_Task
+this macro is used when calling starpu_task_insert(), and must be
+followed by an integer value specifying the worker on which to execute
+the task (as specified by starpu_task::execute_on_a_specific_worker)
+
 \def STARPU_TAG
 \ingroup API_Insert_Task
 this macro is used when calling starpu_task_insert(), and must be followed by a tag.

include/starpu_task_util.h

@@ -1,7 +1,8 @@
 /* StarPU --- Runtime system for heterogeneous multicore architectures.
  *
  * Copyright (C) 2010-2013  Université de Bordeaux 1
- * Copyright (C) 2010, 2011, 2012, 2013  Centre National de la Recherche Scientifique
+ * Copyright (C) 2010-2013  Centre National de la Recherche Scientifique
+ * Copyright (C) 2014       INRIA
  *
  * 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
@@ -45,6 +46,7 @@ void starpu_create_sync_task(starpu_tag_t sync_tag, unsigned ndeps, starpu_tag_t
 #define STARPU_SCHED_CTX	 (12<<16)
 #define STARPU_PROLOGUE_CALLBACK   (13<<16)
 #define STARPU_PROLOGUE_CALLBACK_ARG (14<<16)
+#define STARPU_EXECUTE_ON_WORKER (15<<16)
 
 struct starpu_task *starpu_task_build(struct starpu_codelet *cl, ...);
 int starpu_task_insert(struct starpu_codelet *cl, ...);

mpi/src/starpu_mpi_task_insert.c

@@ -1,7 +1,8 @@
 /* StarPU --- Runtime system for heterogeneous multicore architectures.
  *
- * Copyright (C) 2011, 2012, 2013  Centre National de la Recherche Scientifique
+ * Copyright (C) 2011, 2012, 2013, 2014  Centre National de la Recherche Scientifique
  * Copyright (C) 2011-2013  Université de Bordeaux 1
+ * Copyright (C) 2014 INRIA
  *
  * 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
@@ -395,6 +396,12 @@ int _starpu_mpi_task_decode_v(struct starpu_codelet *codelet, int me, int nb_nod
 			STARPU_ASSERT_MSG(*xrank <= nb_nodes, "Node %d to execute codelet is not a valid node (%d)", *xrank, nb_nodes);
 			*do_execute = 1;
 		}
+		else if (arg_type==STARPU_EXECUTE_ON_WORKER)
+		{
+			// the flag is decoded and set later when
+			// calling function _starpu_task_insert_create()
+			va_arg(varg_list_copy, int);
+		}
 		else if (arg_type==STARPU_R || arg_type==STARPU_W || arg_type==STARPU_RW || arg_type==STARPU_SCRATCH || arg_type==STARPU_REDUX)
 		{
 			starpu_data_handle_t data = va_arg(varg_list_copy, starpu_data_handle_t);
@@ -585,6 +592,12 @@ int _starpu_mpi_task_build_v(MPI_Comm comm, struct starpu_codelet *codelet, stru
 		{
 			va_arg(varg_list_copy, starpu_data_handle_t);
 		}
+		else if (arg_type==STARPU_EXECUTE_ON_WORKER)
+		{
+			// the flag is decoded and set later when
+			// calling function _starpu_task_insert_create()
+			va_arg(varg_list_copy, int);
+		}
 		else if (arg_type==STARPU_HYPERVISOR_TAG)
 		{
 			(void)va_arg(varg_list_copy, int);
@@ -702,6 +715,10 @@ int _starpu_mpi_task_postbuild_v(MPI_Comm comm, struct starpu_codelet *codelet,
 		{
 			va_arg(varg_list_copy, starpu_data_handle_t);
 		}
+		else if (arg_type==STARPU_EXECUTE_ON_WORKER)
+		{
+			va_arg(varg_list_copy, int);
+		}
 		else if (arg_type==STARPU_HYPERVISOR_TAG)
 		{
 			(void)va_arg(varg_list_copy, int);

src/util/starpu_task_insert_utils.c

@@ -1,7 +1,7 @@
 /* StarPU --- Runtime system for heterogeneous multicore architectures.
  *
  * Copyright (C) 2011, 2012, 2013  Centre National de la Recherche Scientifique
- * Copyright (C) 2011  INRIA
+ * Copyright (C) 2011, 2014        INRIA
  *
  * 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
@@ -103,6 +103,10 @@ size_t _starpu_task_insert_get_arg_size(va_list varg_list)
 		{
 			(void)va_arg(varg_list, starpu_data_handle_t);
 		}
+		else if (arg_type==STARPU_EXECUTE_ON_WORKER)
+		{
+			va_arg(varg_list, int);
+		}
 		else if (arg_type==STARPU_SCHED_CTX)
 		{
 			(void)va_arg(varg_list, unsigned);
@@ -202,6 +206,10 @@ int _starpu_codelet_pack_args(void **arg_buffer, size_t arg_buffer_size, va_list
 		{
 			(void)va_arg(varg_list, starpu_data_handle_t);
 		}
+		else if (arg_type==STARPU_EXECUTE_ON_WORKER)
+		{
+			va_arg(varg_list, int);
+		}
 		else if (arg_type==STARPU_SCHED_CTX)
 		{
 			(void)va_arg(varg_list, unsigned);
@@ -346,6 +354,12 @@ void _starpu_task_insert_create(void *arg_buffer, size_t arg_buffer_size, struct
 		{
 			(void)va_arg(varg_list, starpu_data_handle_t);
 		}
+		else if (arg_type==STARPU_EXECUTE_ON_WORKER)
+		{
+			(*task)->workerid = va_arg(varg_list, int);
+			if ((*task)->workerid  != -1)
+				(*task)->execute_on_a_specific_worker = 1;
+		}
 		else if (arg_type==STARPU_SCHED_CTX)
 		{
 			unsigned sched_ctx = va_arg(varg_list, unsigned);