[petsc-users] On the edge of 2^31 unknowns

[hong at aspiritech.org]

Eric:
The nonscalable implementation is robust, and faster for small to medium
size problems, thus we set it as the default. You can switch with
option '-matmatmult_via
scalable', which requires estimate of nonzeros A*B.
The estimate was buggy, not well-tested. If you encounter any problem, let
us know.

Hong

On Mon, Jun 20, 2016 at 10:49 PM, Eric Chamberland <
Eric.Chamberland at giref.ulaval.ca> wrote:

>
>
> Le 2016-06-20 23:37, Barry Smith a écrit :
>
>> On Jun 20, 2016, at 10:32 PM, Eric Chamberland <
>>> Eric.Chamberland at giref.ulaval.ca> wrote:
>>>
>>> ok, but what about -matmatmult_via scalable?
>>>
>>    Both should work. It just may be one is faster or slower than the
>> other depending on the problem size.
>>
> ok, digging further, I found this into blaming the code:
>
> 0fc8cf34 (Hong Zhang       2013-06-27 14:04:58 -0500  696) /* same as
> MatMatMultSymbolic_MPIAIJ_MPIAIJ_nonscalable(), except using LLCondensed to
> avoid O(BN) memory requirement */
>
> But the commit comment says:
> ...
>     rename MatMatMultSymbolic_MPIAIJ_MPIAIJ ->
> MatMatMultSymbolic_MPIAIJ_MPIAIJ_nonscalable (non-default)
>
> But it *is* the default...  since another commit:
>
> commit 0d3441ae8a080c728abf17e90308c510e39e951b
> Author: Hong Zhang <hzhang at mcs.anl.gov>
> Date:   Mon Aug 24 16:40:35 2015 -0500
>
>     add MatPtAPxxx_MPIAIJ_MPIAIJ_new
>
> which changed the behaviour programmed in 0fc8cf34.  Is it normal?
>
> Eric
>
>
>
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