Hi all,
I would like to extract a subvector of a distributed PetscVector using the
create_subvector routine. My example programs looks as follows:
#include <iostream>
#include <algorithm>
#include <math.h>
#include "libmesh/libmesh.h"
#include "libmesh/mesh.h"
#include "libmesh/mesh_generation.h"
#include "libmesh/linear_implicit_system.h"
#include "libmesh/equation_systems.h"
#include "libmesh/numeric_vector.h"
#include "libmesh/elem.h"
#include "libmesh/dof_map.h"
#include "libmesh/petsc_vector.h"
using namespace libMesh;
int main (int argc, char** argv)
{
LibMeshInit init (argc, argv);
Mesh mesh(init.comm());
MeshTools::Generation::build_square (mesh,10,10,-1., 1.,-1., 1., QUAD4);
mesh.print_info();
EquationSystems es(mesh);
const std::string system_name = "Poisson";
es.add_system<LinearImplicitSystem> (system_name);
es.get_system(system_name).add_variable("u", FIRST);
es.init();
es.print_info();
const DofMap & dof_map = es.get_system(system_name).get_dof_map();
UniquePtr< NumericVector< Number > > x =
es.get_system(system_name).solution->zero_clone();
PetscVector< Number > y( mesh.comm(), x->size() );
std::vector< dof_id_type > dof_indices;
std::set<dof_id_type> some_dof_set;
MeshBase::const_element_iterator el =
mesh.active_local_elements_begin();
const MeshBase::const_element_iterator end_el =
mesh.active_local_elements_end();
// create some dofs local to each processor
for ( ; el != end_el ; ++el)
{
const Elem * elem = *el;
dof_map.dof_indices (elem, dof_indices);
if ( elem->centroid()(0) < 0. )
some_dof_set.insert( dof_indices.begin(), dof_indices.end() );
}
// build a subvector local to each procoessor
std::vector< dof_id_type > some_dofs( some_dof_set.begin(),
some_dof_set.end() );
x->create_subvector( y, some_dofs );
std::cout << "PROC = " << mesh.comm().rank()
<< ": local size of some_dofs = " << some_dofs.size() << std::endl;
std::cout << "PROC = " << mesh.comm().rank()
<< ": global size of y = " << y.size() << std::endl;
std::cout << "PROC = " << mesh.comm().rank()
<< ": local size of y = " << y.local_size() << std::endl;
std::cout << "PROC = " << mesh.comm().rank()
<< ": (first,last) local index of y = ("
<< y.first_local_index() << ", " << y.last_local_index() << ")" <<
std::endl;
return 0;
}
The output that I get when running the program with
mpirun -np 2 ./ex_create_subvector-opt --keep-cout
is
elem_dimensions()={2}
spatial_dimension()=2
n_nodes()=121
n_local_nodes()=67
n_elem()=100
n_local_elem()=50
n_active_elem()=100
n_subdomains()=1
n_partitions()=2
n_processors()=2
n_threads()=1
processor_id()=0
Mesh Information:
elem_dimensions()={2}
spatial_dimension()=2
n_nodes()=121
n_local_nodes()=54
n_elem()=100
n_local_elem()=50
n_active_elem()=100
n_subdomains()=1
n_partitions()=2
n_processors()=2
n_threads()=1
processor_id()=1
EquationSystems
n_systems()=1
System #0, "Poisson"
Type "LinearImplicit"
Variables="u"
Finite Element Types="LAGRANGE", "JACOBI_20_00"
Infinite Element Mapping="CARTESIAN"
Approximation Orders="FIRST", "THIRD"
n_dofs()=121
n_local_dofs()=67
n_constrained_dofs()=0
n_local_constrained_dofs()=0
n_vectors()=1
n_matrices()=1
DofMap Sparsity
Average On-Processor Bandwidth <= 7.70248
Average Off-Processor Bandwidth <= 0.545455
Maximum On-Processor Bandwidth <= 11
Maximum Off-Processor Bandwidth <= 4
DofMap Constraints
Number of DoF Constraints = 0
Number of Node Constraints = 0
EquationSystems
n_systems()=1
System #0, "Poisson"
Type "LinearImplicit"
Variables="u"
Finite Element Types="LAGRANGE", "JACOBI_20_00"
Infinite Element Mapping="CARTESIAN"
Approximation Orders="FIRST", "THIRD"
n_dofs()=121
n_local_dofs()=54
n_constrained_dofs()=0
n_local_constrained_dofs()=0
n_vectors()=1
n_matrices()=1
DofMap Sparsity
Average On-Processor Bandwidth <= 7.70248
Average Off-Processor Bandwidth <= 0.545455
Maximum On-Processor Bandwidth <= 11
Maximum Off-Processor Bandwidth <= 4
DofMap Constraints
Number of DoF Constraints = 0
Number of Node Constraints = 0
PROC = 0: local size of some_dofs = 10
PROC = 0: global size of y = 121
PROC = 0: local size of y = 121
PROC = 0: (first,last) local index of y = (0, 121)
PROC = 1: local size of some_dofs = 62
PROC = 1: global size of y = 121
PROC = 1: local size of y = 121
PROC = 1: (first,last) local index of y = (0, 121)
Apparently, the vector y is not distributed correctly to the processors. Is
this a bug?
Best,
Jonas
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