Hi Gennadiy,
If you're wanting to print only "possibly" non-zero entries in the
sparse-matrix, you can check the underlying sparsity pattern and
determine whether the entry exists or not:
sparse_matrix.get_sparsity_pattern().exists(i,j)
This returns true if the entry is writable and false if the entry does
not exist (i.e. always zero).
Regards,
J-P
On Fri 26 Aug 2011 14:49:55 SAST, Markus Bürg wrote:
Hello Gennadiy,
unfortunately you have to check the value of the entries:
if (std::abs (sparse_matrix.el (i,j)) > 1e-15)
std::cout ...
Best Regards,
Markus
Am 26.08.11 14:02, schrieb Gennadiy Rishkin:
Hi
I'm trying to iterate over the nonzero entries in a matrix but the
code below gives all entries including zero entries. How do I obtain
the values and indexes of the nonzero entries?
The test system_matrix is from step-2 (no refinement):
6.667e-01 0.000e+00 0.000e+00 0.000e+00
0.000e+00 6.667e-01 0.000e+00 0.000e+00
0.000e+00 0.000e+00 6.667e-01 0.000e+00
0.000e+00 0.000e+00 0.000e+00 6.667e-01
for (unsigned int i = 0; i < 1 /*system_matrix.m()*/; ++i) {
std::cout << "Row " << i << " has " << sparsity_pattern.row_length(i)
<< " entries." << std::endl;
SparsityPattern::row_iterator rowBegin = sparsity_pattern.row_begin(i);
SparsityPattern::row_iterator rowEnd = sparsity_pattern.row_end(i);
for ( ; rowBegin != rowEnd; ++rowBegin) {
if ( sparsity_pattern.exists( i, sparsity_pattern.column_number(i,
*rowBegin) ) )
std::cout << *rowBegin << std::endl;
}
}
OUTPUT:
Row 0 has 4 entries.
0
1
2
3
Gennadiy
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