Hi there,
I am trying to build a parallel PETSc sparse matrix by building a local
sparsity pattern and subsequently distributing the pattern to all processes so
I then have the full sparsity pattern for the PETSc sparse matrix (I read this
needs to be done but please correct me if I am wrong). When I try to reinit the
PETSc sparse matrix I get a segfault so I am hunting down the problem.
My understanding for “distribute_sparsity_pattern” is it sends local sparsity
patterns to all other processes and saves the full global pattern in the
dynamic sparsity pattern you passed in. So I figured that after I call this
function, my local number of rows should be the global number of rows but the
number of rows is the same as before I called this function (i.e. the actual
local number of rows) so I think I am not using this function correctly and my
PETSc sparse matrix doesn’t have the global dynamic sparsity pattern I think it
must have, which results in a segfault.
NOTE: The matrix is a square matrix with rows and columns of size “nbas *
nchannels” and the rows are divided amongst the processes.
Here is the code for distributing my locally built sparsity pattern dsp:
IndexSet local_owned( nbas * nchannels * nbas * nchannels ); \\ allocate global
sized index set
local_owned.add_range( LocalStart(), LocalEnd() ); \\ start of local row first
column and end of last local row at last column
SparsityTools::distribute_sparsity_pattern( dsp, local_owned, comm, local_owned
);
Here is the code for initializing my PETSc sparse matrix:
std::vector<size_type> local_rows_per_process( num_procs); // allocate a vector
of length number of process
std::vector<size_type> local_columns_per_process( num_procs, nbas * nchannels);
// columns are full length and rows are divided by num_procs
for(int i=0; i < num_procs; ++i )
{
local_rows_per_process[ i ] = i * local_rows; // Saw this in a test but
initially thought this should just all be local_rows for each i
}
Matrix.reinit( comm, dsp, local_rows_per_process, local_columns_per_process,
my_proc);
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