[petsc-users] PetscInt overflow

[Jan Grießer]

With more than 1 MPI process you mean i should use spectrum slicing in
divide the full problem in smaller subproblems?
The --with-64-bit-indices is not a possibility for me since i configured
petsc with mumps, which does not allow to use the 64-bit version (At least
this was the error message when i tried to configure PETSc )

Am Mi., 17. Okt. 2018 um 18:24 Uhr schrieb Jose E. Roman <jroman at dsic.upv.es
>:

> To use BVVECS just add the command-line option -bv_type vecs
> This causes to use a separate Vec for each column, instead of a single
> long Vec of size n*m. But it is considerably slower than the default.
>
> Anyway, for such large problems you should consider using more than 1 MPI
> process. In that case the error may disappear because the local size is
> smaller than 768000.
>
> Jose
>
>
> > El 17 oct 2018, a las 17:58, Matthew Knepley <knepley at gmail.com>
> escribió:
> >
> > On Wed, Oct 17, 2018 at 11:54 AM Jan Grießer <
> griesser.jan at googlemail.com> wrote:
> > Hi all,
> > i am using slepc4py and petsc4py to solve for the smallest real
> eigenvalues and eigenvectors. For my test cases with a matrix A of the size
> 30k x 30k solving for the smallest soutions works quite well, but when i
> increase the dimension of my system to around A = 768000 x 768000 or 3
> million x 3 million and ask for the smallest real 3000 (the number is
> increasing with increasing system size) eigenvalues and eigenvectors i get
> the output (for the 768000):
> >  The product 4001 times 768000 overflows the size of PetscInt; consider
> reducing the number of columns, or use BVVECS instead
> > i understand that the requested number of eigenvectors and eigenvalues
> is causing an overflow but i do not understand the solution of the problem
> which is stated in the error message. Can someone tell me what exactly
> BVVECS is and how i can use it? Or is there any other solution to my
> problem ?
> >
> > You can also reconfigure with 64-bit integers: --with-64-bit-indices
> >
> >   Thanks,
> >
> >     Matt
> >
> > Thank you very much in advance,
> > Jan
> >
> >
> >
> > --
> > What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> > -- Norbert Wiener
> >
> > https://www.cse.buffalo.edu/~knepley/
>
>
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