[petsc-users] info about MatPreallocateInitialize/Finalize

[Barletta, Ivano]

Dear all

How does MatPreallocateInitialize/Finalize work?

I don't see any reference for examples in the
online manual, soI've browsed the source code
to see whetherthe routine is used and how

As far as I understood it works this way:

    call MatPreallocateInitialize(comm, rows, cols, d_nz,o_nz,ierr)

    ! do something to calculate d_nz and o_nz

    call MatXXXSetPreallocation
    call MatPreallocateFinalize

It is not that clear the way d_nz and o_nz are
computed. Do I need to provide them myself?
(in that case what would be the point of using
MatPreallocateInitialize/Finalize?)

Thanks
Ivano
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