[petsc-users] MatMPIAIJSetPreallocation question

[Xiangdong]

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?

Thank you.

Best,
Xiangdong
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