----- Original Message ----- From: owner-petsc-users at mcs.anl.gov <[email protected]> To: petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov> Sent: Tue Sep 23 21:38:31 2008 Subject: Extend preallocation
Dear Petsc users, I would like to compute the sparse projection matrix Q=Id - Pt*A*P. Pt*A*P is very well computed by MatMatMult ; then I would like to use MatShift in order to complete the computation. Unfortunately, Pt*A*P has lots of zeros on its diagonal, thus MatShift is very slow due to inapropriate preallocation. Since the initial preallocation of Pt*A*P is very good, I would to know if there is a method allowing to get the allocation data structure and to extend it in order to preallocate the diagonal terms. Best regards, Nicolas -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20080923/927c4a19/attachment.htm>
