Hi Barry, Thanks for your response. So these extra allocated memory is just a waste of memory, but no harm for other mat related computation. Is it correct?
Thank you. Xiangdong On Fri, Aug 4, 2017 at 4:52 PM, Barry Smith <bsm...@mcs.anl.gov> wrote: > > > On Aug 4, 2017, at 2:52 PM, Xiangdong <epsco...@gmail.com> wrote: > > > > Hello everyone, > > > > I have a quick questions on the MatMPIAIJSetPreallocation. If we do not > pass the exact number of nonzeros for o_nnz and d_nnz, (for example, > MAT_INFO_NZ_ALLOCATED is 50% more than MAT_INFO_NZ_USED), will the > performance of MatMult be affected? What effect will these allocated but > unused memory cause? > > It is not a big deal to have extra memory, it won't slow things down. > If you under estimate it can slow things down a lot. > > > > > Thank you. > > > > Best, > > Xiangdong > >
