Path: blob/main/example/cmesh/t8_cmesh_create_partitioned.cxx
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/*
This file is part of t8code.
t8code is a C library to manage a collection (a forest) of multiple
connected adaptive space-trees of general element types in parallel.
Copyright (C) 2015 the developers
t8code is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
t8code 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with t8code; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <t8_vtk/t8_vtk_writer.h>
/* Create a coarse mesh that is partitioned across two processes
* (if mpisize >= 2).
*
* To keep the example short, we only create the connectivity and
* do not equip this cmesh with coordinates.
* See the other examples or the t8_cmesh_new_function in t8_cmesh.cxx
* for coordinate handling.
*/
void
t8_cmesh_create_partitioned (sc_MPI_Comm comm)
{
int mpisize, mpirank;
t8_cmesh_t cmesh;
t8_cmesh_init (&cmesh);
/* We create this coarse mesh (numbers are tree numbers):
*
* x ----- x - x
* | |1 /|
* | 0 | / |
* | |/ 2|
* x ----- x - x
* | 5 / | |
* | / 4 | 3 |
* | / | |
* x ----- x - x
*
* If the number of calling processes is > 1, then the coarse mesh
* is created partitioned. In the partition process 0 gets trees 0, 1, 2
* and process 1 gets trees 3, 4, 5. The other process get no trees.
* Thus process 0 has ghost trees 3 and 5. Process 1 has ghost trees 0 and 2.
*
* The tree corners are set as follows:
*
* quads: 2 -- 3 triangles: 1-2 2
* | | |/ /|
* 0 -- 1 0 0-1
*
*/
/* Get the number of processes */
sc_MPI_Comm_size (comm, &mpisize);
/* Get this processes rank */
sc_MPI_Comm_rank (comm, &mpirank);
if (mpisize > 1) {
/* We have more than 1 process. Create the cmesh partitioned */
if (mpirank == 0) {
/* Set the classes of the owned trees */
t8_cmesh_set_tree_class (cmesh, 0, T8_ECLASS_QUAD);
t8_cmesh_set_tree_class (cmesh, 1, T8_ECLASS_TRIANGLE);
t8_cmesh_set_tree_class (cmesh, 2, T8_ECLASS_TRIANGLE);
/* Set the classes of the ghost trees */
t8_cmesh_set_tree_class (cmesh, 3, T8_ECLASS_QUAD);
t8_cmesh_set_tree_class (cmesh, 5, T8_ECLASS_TRIANGLE);
/* Set the face-to-face connections of the owned trees */
t8_cmesh_set_join (cmesh, 0, 1, 1, 2, 0); /* tree 0 - tree 1 */
t8_cmesh_set_join (cmesh, 1, 2, 1, 1, 0); /* tree 1 - tree 2 */
/* Set the face-to-face connections between owned and ghost trees */
t8_cmesh_set_join (cmesh, 0, 5, 2, 0, 0); /* tree 0 - tree 5 */
t8_cmesh_set_join (cmesh, 2, 3, 2, 3, 0); /* tree 2 - tree 3 */
/* Tell the cmesh that it is partitioned and trees 0 to 3 are local */
t8_cmesh_set_partition_range (cmesh, 3, 0, 2);
}
else if (mpirank == 1) {
/* Set the classes of the owned trees */
t8_cmesh_set_tree_class (cmesh, 3, T8_ECLASS_QUAD);
t8_cmesh_set_tree_class (cmesh, 4, T8_ECLASS_TRIANGLE);
t8_cmesh_set_tree_class (cmesh, 5, T8_ECLASS_TRIANGLE);
/* Set the classes of the ghost trees */
t8_cmesh_set_tree_class (cmesh, 0, T8_ECLASS_QUAD);
t8_cmesh_set_tree_class (cmesh, 2, T8_ECLASS_TRIANGLE);
/* Set the face-to-face connections of the owned trees */
t8_cmesh_set_join (cmesh, 3, 4, 0, 0, 0); /* tree 3 - tree 4 */
t8_cmesh_set_join (cmesh, 4, 5, 1, 1, 0); /* tree 4 - tree 5 */
/* Set the face-to-face connections between owned and ghost trees */
t8_cmesh_set_join (cmesh, 5, 0, 0, 2, 0); /* tree 5 - tree 0 */
t8_cmesh_set_join (cmesh, 3, 2, 3, 2, 0); /* tree 3 - tree 2 */
/* Tell the cmesh that it is partitioned and trees 4 to 6 are local */
t8_cmesh_set_partition_range (cmesh, 3, 3, 5);
}
else {
/* mpirank is > 2 */
/* Tell the cmesh that it is partitioned and it has not trees */
t8_cmesh_set_partition_range (cmesh, 3, 6, 5);
/* Tell the cmesh that its 2-dimensional.
* Since we have no trees here, we cannot deduce this from context */
t8_cmesh_set_dimension (cmesh, 2);
}
}
else {
/* we have exactly 1 process and just build the cmesh with all tree */
/* Set the classes of the trees */
t8_cmesh_set_tree_class (cmesh, 0, T8_ECLASS_QUAD);
t8_cmesh_set_tree_class (cmesh, 1, T8_ECLASS_TRIANGLE);
t8_cmesh_set_tree_class (cmesh, 2, T8_ECLASS_TRIANGLE);
t8_cmesh_set_tree_class (cmesh, 3, T8_ECLASS_QUAD);
t8_cmesh_set_tree_class (cmesh, 4, T8_ECLASS_TRIANGLE);
t8_cmesh_set_tree_class (cmesh, 5, T8_ECLASS_TRIANGLE);
/* Set the face connections */
/* Set the face-to-face connections of the owned trees */
t8_cmesh_set_join (cmesh, 0, 1, 1, 2, 0); /* tree 0 - tree 1 */
t8_cmesh_set_join (cmesh, 0, 5, 2, 0, 0); /* tree 0 - tree 5 */
t8_cmesh_set_join (cmesh, 1, 2, 1, 1, 0); /* tree 1 - tree 2 */
t8_cmesh_set_join (cmesh, 2, 3, 2, 3, 0); /* tree 2 - tree 3 */
t8_cmesh_set_join (cmesh, 3, 4, 0, 0, 0); /* tree 3 - tree 4 */
t8_cmesh_set_join (cmesh, 4, 5, 1, 1, 0); /* tree 4 - tree 5 */
}
/* Create the cmesh */
t8_cmesh_commit (cmesh, comm);
/* Clean-up */
t8_cmesh_destroy (&cmesh);
}
int
main (int argc, char **argv)
{
int mpiret;
mpiret = sc_MPI_Init (&argc, &argv);
SC_CHECK_MPI (mpiret);
sc_init (sc_MPI_COMM_WORLD, 1, 1, NULL, SC_LP_ESSENTIAL);
t8_init (SC_LP_DEFAULT);
t8_global_essentialf (
"This program creates a coarse mesh that is partitioned across the processes.\n The coarse mesh consists of six "
"trees.\nTrees 0,1,2 are assigned to process 0.\nTrees 3,4,5 to process 1.\n The remaining processes do not have "
"any trees.\n If called with only 1 process, the coarse mesh is not partitioned.\n");
t8_cmesh_create_partitioned (sc_MPI_COMM_WORLD);
sc_finalize ();
mpiret = sc_MPI_Finalize ();
SC_CHECK_MPI (mpiret);
return 0;
}