[petsc-users] difference on MATLAB backslash and PETSc/external solvers

[Umut Tabak]

On 04/15/2011 08:00 PM, Barry Smith wrote:
>     What do you mean in the debug mode?  To do any fair comparisons of times you should have ./configure PETSc with --with-debugging=0
>
>    
Dear Barry, Thx.
Ok, this is what I meant.
>     Reason of what?
>
>    
The difference...
>     Different solvers will give different solution times, this is perfectly normal. In fact sometimes for different matrices different solvers will actually be best for different matrices?
>
>     Are you asking why UMFPack in Matlab does much faster (it seems) than the one used by PETSc? The likely answer is that the Matlab folks tweak the hell out of it to get good performance and when Tim Davis says "UMFPACK is in Matlab" actually means he gave something to Matlab and they improved it.
ok, fine, this answers my question.
>   It is unlikely that Matlab just uses the downloadable open source UMFPACK that PETSc uses.
>