regression_based: make sure we reuse our buffers

Otherwise the prefetch would preallocate all buffers in advance.

tests/perfmodels/regression_based_check.c

@@ -73,7 +73,7 @@ static struct starpu_codelet memset_cl =
 	.cpu_funcs_name = {"memset_cpu"},
 	.model = &model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static struct starpu_codelet nl_memset_cl =
@@ -82,7 +82,7 @@ static struct starpu_codelet nl_memset_cl =
 	.cpu_funcs_name = {"memset_cpu"},
 	.model = &nl_model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static void test_memset(int nelems, struct starpu_codelet *codelet)

tests/perfmodels/regression_based_energy.c

@@ -109,7 +109,7 @@ static struct starpu_codelet memset_cl =
 	.cpu_funcs_name = {"memset0_cpu", "memset_cpu"},
 	.model = &model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static struct starpu_codelet nl_memset_cl =
@@ -119,7 +119,7 @@ static struct starpu_codelet nl_memset_cl =
 	.model = &nl_model,
 	.energy_model = &nl_energy_model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static void test_memset(int nelems, struct starpu_codelet *codelet)

tests/perfmodels/regression_based_gpu.c

@@ -106,7 +106,7 @@ static struct starpu_codelet memset_cl =
 	.cpu_funcs_name = {"memset0_cpu", "memset_cpu"},
 	.model = &model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static struct starpu_codelet nl_memset_cl =
@@ -123,7 +123,7 @@ static struct starpu_codelet nl_memset_cl =
 	.cpu_funcs_name = {"memset0_cpu", "memset_cpu"},
 	.model = &nl_model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static void test_memset(int nelems, struct starpu_codelet *codelet)

tests/perfmodels/regression_based_memset.c

@@ -116,7 +116,7 @@ static struct starpu_codelet memset_cl =
 	.model = &model,
 	.energy_model = &energy_model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static struct starpu_codelet nl_memset_cl =
@@ -134,7 +134,7 @@ static struct starpu_codelet nl_memset_cl =
 	.model = &nl_model,
 	.energy_model = &nl_energy_model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static void test_memset(int nelems, struct starpu_codelet *codelet)

tests/perfmodels/regression_based_multiimpl.c

@@ -108,7 +108,7 @@ static struct starpu_codelet memset_cl =
 	.cpu_funcs_name = {"memset0_cpu", "memset_cpu"},
 	.model = &model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static struct starpu_codelet nl_memset_cl =
@@ -118,7 +118,7 @@ static struct starpu_codelet nl_memset_cl =
 	.model = &nl_model,
 	.energy_model = &nl_energy_model,
 	.nbuffers = 1,
-	.modes = {STARPU_W}
+	.modes = {STARPU_SCRATCH}
 };
 
 static void test_memset(int nelems, struct starpu_codelet *codelet)