On 04/12/2014 06:10 PM, Barry Smith wrote:
Patrick,
Currently it is supported for MatSetValues_SeqAIJ() and
MatSetValues_MPIAIJ(). It is not handled for BAIJ and SBAIJ, the code while
crash with segv in those cases (since we don’t check for a valid v pointer
before use :-). But support could easily be added for BAIJ and SBAIJ with
just a few lines of code.
MatSetValuesBlocked() does not have this kind of support and adding it
would be cumbersome.
So I guess the question is does this “feature” add useful functionality
that makes the slightly more complex code worthwhile? Or is it an oddball thing
that should be removed? As the cool kids would say “what is the use case for
this feature?”.
I’m fine with adding support for BAIJ and SBAIJ and documenting it but
then I am also fine with removing it though I suspect it is used somewhere in
PETSc and thus that code would need to be located and changed if it is removed.
Hi Barry,
I was writing (new) code which do the firsts MatSetValues after the
MatXAIJSetPreallocation. We have to do this because the "real"
non-zeros will be added later by a mix of ADD_VALUES and
INSERT_VALUES... which would prevent us to "lock" the matrix
(MatSetOption(aMatricePETSc, MAT_NEW_NONZERO_LOCATION_ERR, PETSC_TRUE)
because this option must be passed after the first MatAssemblyEnd()...
but all the non-zeros are "triggered" only after this "mixed" assembly...
In other words, we have to do a "fake" assembly with all "0" to cover
all non-zeros that will be in fact added later... So we have to create
many "fake" elementary matrices to pass for assembly... that is why
Patrick was asking if the feature was supported... It would save us from
creating the fake matrices... Or maybe there is a better solution?...
Thanks,
Eric
Barry
On Apr 11, 2014, at 12:51 PM, Patrick Lacasse <[email protected]>
wrote:
Hi,
I see that implementation of MatSetValues handles a special case when one
passes a null pointer v=0.
In this case, it is considered that all values are 0.
But the documentation doesn't seems to talk about it :
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSetValues.html
Is it a feature that we can use?
Should it be added to the doc?
Patrick Lacasse
