examples: add a filter example to show how to submit a task accessing in read mode a data which has been asynchronously partitioned

examples/Makefile.am

@@ -225,6 +225,7 @@ STARPU_EXAMPLES +=				\
 	cpp/incrementer_cpp			\
 	cpp/add_vectors				\
 	cpp/add_vectors_interface		\
+	filters/fread				\
 	filters/fvector				\
 	filters/fblock				\
 	filters/fmatrix				\

examples/filters/fread.c

@@ -0,0 +1,128 @@
+/* StarPU --- Runtime system for heterogeneous multicore architectures.
+ *
+ * Copyright (C) 2020       Université de Bordeaux, CNRS (LaBRI UMR 5800), 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
+ * 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 <starpu.h>
+
+#define NX    20
+#define PARTS 2
+
+#define FPRINTF(ofile, fmt, ...) do { if (!getenv("STARPU_SSILENT")) {fprintf(ofile, fmt, ## __VA_ARGS__); }} while(0)
+
+void display_func(void *buffers[], void *cl_arg)
+{
+        unsigned i;
+
+        /* length of the vector */
+        unsigned n = STARPU_VECTOR_GET_NX(buffers[0]);
+        /* local copy of the vector pointer */
+        int *val = (int *)STARPU_VECTOR_GET_PTR(buffers[0]);
+
+	FPRINTF(stderr, "vector with n=%u : ", n);
+        for (i = 0; i < n; i++)
+		FPRINTF(stderr, "%5d ", val[i]);
+	FPRINTF(stderr, "\n");
+}
+
+void cpu_func(void *buffers[], void *cl_arg)
+{
+        unsigned i;
+
+        /* length of the vector */
+        unsigned n = STARPU_VECTOR_GET_NX(buffers[0]);
+        /* local copy of the vector pointer */
+        int *val = (int *)STARPU_VECTOR_GET_PTR(buffers[0]);
+
+	FPRINTF(stderr, "computing on vector with n=%u\n", n);
+        for (i = 0; i < n; i++)
+                val[i] *= 2;
+}
+
+int main(void)
+{
+	int i;
+        int vector[NX];
+        starpu_data_handle_t handle;
+	starpu_data_handle_t subhandles[PARTS];
+	int ret;
+
+        struct starpu_codelet cl =
+	{
+                .cpu_funcs = {cpu_func},
+                .cpu_funcs_name = {"cpu_func"},
+                .nbuffers = 1,
+		.modes = {STARPU_RW},
+		.name = "vector_scal"
+        };
+        struct starpu_codelet print_cl =
+	{
+                .cpu_funcs = {display_func},
+                .cpu_funcs_name = {"display_func"},
+                .nbuffers = 1,
+		.modes = {STARPU_R},
+		.name = "vector_display"
+        };
+
+        for(i=0 ; i<NX ; i++) vector[i] = i;
+
+	ret = starpu_init(NULL);
+	if (ret == -ENODEV)
+		exit(77);
+	STARPU_CHECK_RETURN_VALUE(ret, "starpu_init");
+
+	/* Declare data to StarPU */
+	starpu_vector_data_register(&handle, STARPU_MAIN_RAM, (uintptr_t)vector, NX, sizeof(vector[0]));
+
+        /* Partition the vector in PARTS sub-vectors */
+	struct starpu_data_filter f =
+	{
+		.filter_func = starpu_vector_filter_block,
+		.nchildren = PARTS
+	};
+	starpu_data_partition_plan(handle, &f, subhandles);
+
+	ret = starpu_task_insert(&print_cl,
+				 STARPU_R, handle,
+				 0);
+	if (ret == -ENODEV) goto enodev;
+	STARPU_CHECK_RETURN_VALUE(ret, "starpu_task_submit");
+
+        /* Submit a task on each sub-vector */
+	for (i=0; i<PARTS; i++)
+	{
+		ret = starpu_task_insert(&cl,
+					 STARPU_RW, subhandles[i],
+					 0);
+		if (ret == -ENODEV) goto enodev;
+		STARPU_CHECK_RETURN_VALUE(ret, "starpu_task_submit");
+	}
+
+	ret = starpu_task_insert(&print_cl,
+				 STARPU_R, handle,
+				 0);
+	if (ret == -ENODEV) goto enodev;
+	STARPU_CHECK_RETURN_VALUE(ret, "starpu_task_submit");
+
+	starpu_data_partition_clean(handle, PARTS, subhandles);
+        starpu_data_unregister(handle);
+	starpu_shutdown();
+
+	return 0;
+
+enodev:
+	FPRINTF(stderr, "WARNING: No one can execute this task\n");
+	starpu_shutdown();
+	return 77;
+}