[petsc-users] Memory allocation failed

[Jed Brown]

On Wed, Aug 31, 2011 at 07:52, Dominik Szczerba <dominik at itis.ethz.ch>wrote:

> I am getting the below cited error for a big linear problem. Would
> that mean int overflow and indicate the need for
> --with-64-bit-indices?
>

Yes, likely.


> Obviously it will elevate the memory
> requirements, but will it also reduce the performance?
>

Try it. Performance for sparse linear algebra is mostly limited by memory
already. Using 64-bit indices increases the cost per nonzero in AIJ format,
sizeof(PetscScalar)+sizeof(PetscInt), typically from 12 to 16 bytes. If you
use BAIJ, the 64-bit indices will make much less difference.
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