[petsc-users] randomness from MATSOLVERPACKAGE

Hui Zhang mike.hui.zhang at hotmail.com
Wed May 30 09:48:56 CDT 2012

On May 30, 2012, at 4:40 PM, Jed Brown wrote:

> On Wed, May 30, 2012 at 9:37 AM, Hui Zhang <mike.hui.zhang at hotmail.com> wrote:
>> How is the matrix assembled?
> In a deterministic way.
> Do you use ADD_VALUES with off-process entries? If so, the message order may be different. You can also add -vecscatter_reproduce to make VecScatter with ADD_VALUES process the messages in a static order instead of in the order they arrive (somewhat slower).

Thanks for details. For the moment, it seems not necessary for me.

>> How different?
> Not very much. The last residual can vary in its trailing digits, e.g. from 6.5819e-7 to 6.5820e-7
> This looks fine.

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