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@@ -191,6 +191,63 @@ StarPU provides various interfaces and filters for matrices, vectors, etc.,
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but applications can also write their own data interfaces and filters, see
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<c>examples/interface</c> and <c>examples/filters/custom_mf</c> for an example.
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+\section MultipleView Multiple views
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+
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+Partitioning is synchronous, which can be a problem for dynamic applications.
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+Another way is to register several views on the same piece of data.
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+<c>fmultiple_manual</c> is a complete example using this technique.
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+
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+In short, we first register the same matrix several times:
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+
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+\code{.c}
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+starpu_matrix_data_register(&handle, STARPU_MAIN_RAM, (uintptr_t)matrix, NX, NX, NY, sizeof(matrix[0]));
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+
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+for (i = 0; i < PARTS; i++)
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+ starpu_matrix_data_register(&vert_handle[i], STARPU_MAIN_RAM, (uintptr_t)&matrix[0][i*(NX/PARTS)], NX, NX/PARTS, NY, sizeof(matrix[0][0]));
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+\endcode
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+
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+Since StarPU is not aware that the two handles are actually pointing to the same
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+data, we have a danger of inadvertently submitting tasks to both views, which
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+will bring a mess since StarPU will not guarantee any coherency between the two
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+views. To make sure we don't do this, we invalidate the view that we will not
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+use:
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+
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+\code{.c}
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+for (i = 0; i < PARTS; i++)
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+ starpu_data_invalidate(vert_handle[i]);
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+\endcode
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+
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+Then we can safely work on <c>handle</c>.
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+
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+When we want to switch to the vertical slice view, all we need to do is bring
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+coherency between them by running an empty task on the home node of the data:
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+
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+\code{.c}
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+void empty(void *buffers[] STARPU_ATTRIBUTE_UNUSED, void *cl_arg STARPU_ATTRIBUTE_UNUSED)
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+{ }
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+struct starpu_codelet cl_switch =
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+{
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+ .cpu_funcs = {empty},
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+ .nbuffers = STARPU_VARIABLE_NBUFFERS,
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+};
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+
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+ret = starpu_task_insert(&cl_switch, STARPU_RW, handle,
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+ STARPU_W, vert_handle[0],
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+ STARPU_W, vert_handle[1],
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+ 0);
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+\endcode
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+
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+The execution of the <c>switch</c> task will get back the matrix data into the
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+main memory, and thus the vertical slices will get the updated value there.
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+
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+Again, we prefer to make sure that we don't accidentally access the matrix through the whole-matrix handle:
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+
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+\code{.c}
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+starpu_data_invalidate_submit(handle);
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+\end
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+
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+And now we can start using vertical slices, etc.
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+
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\section DataReduction Data Reduction
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In various cases, some piece of data is used to accumulate intermediate
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