> On Jun 30, 2016, at 2:40 PM, Hassan Raiesi > <hassan.rai...@aero.bombardier.com> wrote: > > Hello, > > We are using PETSC in our CFD code, and noticed that using > “MatCreateMPIAIJWithSplitArrays” is almost 60% faster for large problem size > (i.e DOF > 725M, using GAMG each time-step only takes 5sec, compared to 8.3 > sec when assembling the matrix one row at a time using matsetvaluesblocked() > as recommended). > > The problem is that the memory usage goes up after each call to > MatCreateMPIAIJWithSplitArrays to update the matrix values. As > MatCreateMPIAIJWithSplitArrays is not supposed to copy the values, do we need > to call it each time to update the values? We tried to just update the values > of the diagonal and off-diagonal part of the arrays passed to > “MatCreateMPIAIJWithSplitArrays”, (the sparsity structure is fixed) but it > looks like that the values are not updated, what is the proper way to update > the values of the matrix created by MatCreateMPIAIJWithSplitArrays?
Since you have direct access to the two numeric arrays passed to MatCreateMPIAIJWithSplitArrays() you can simply change the values in those locations AND THEN immediately CALL MatAssemblyBegin/MatAssemblyEnd() on the matrix; this will increase the the PETSc object state value for the matrix so the matrix routines (and preconditioner) will know you changed the matrix values. If you don't call the MatAssemblyBegin/MatAssemblyEnd() the preconditioner will think the matrix has not been changed so just use its old values as you observed. Barry Of course if you change any nonzero locations in the matrix you need to destroy the matrix and call MatCreateMPIAIJWithSplitArrays() again. > > > Thank you > > Hassan Raiesi, > Advanced Aerodynamics Department > Bombardier Aerospace > > hassan.rai...@aero.bombardier.com > > 2351 boul. Alfred-Nobel (BAN1) > Ville Saint-Laurent, Québec, H4S 2A9 > > > > Tél. > 514-855-5001 # 62204 > > > > <image001.png> > > > CONFIDENTIALITY NOTICE - This communication may contain privileged or > confidential information. > If you are not the intended recipient or received this communication by > error, please notify the sender > and delete the message without copying, forwarding and/or disclosing it.
