[petsc-users] PetscInt overflow

[Matthew Knepley]

On Fri, Oct 19, 2018 at 5:01 AM Jan Grießer <griesser.jan at googlemail.com>
wrote:

> 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 )
>

I believe you can replace MUMPS with SuperLU_dist for 64-bit ints.

   Matt


> 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/
>>
>>

-- 
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/ <http://www.cse.buffalo.edu/~knepley/>
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