[petsc-users] Mixed 32-bit and 64-bit indices

Jed Brown jed at 59A2.org
Mon Nov 8 04:22:25 CST 2010

On Mon, Nov 8, 2010 at 09:05, Daniel Langr <daniel.langr at gmail.com> wrote:

> is there any way to use 32-bit integers for indexing rows/columns and
> 64-bit integers for indexing nonzeros at the same time in PETSc? I have a
> matrix with 4,559,168,066 nonzeros but only 448,797 rows/columns. For a
> general CSR scheme, the memory savings are almost 25% when using 32-bit
> integers compared to 64-bit for indexing columns, which is really a lot of
> memory.

Are you running in serial?  As long as the local part of any matrix has less
than 2B entries (which would cost more than 24 GiB to store) and the global
problem has dimension less than 2B, you should be fine using 32-bit indices.

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