[petsc-users] PetscInt overflow

[Smith, Barry F.]

> On Oct 19, 2018, at 7:56 AM, Zhang, Junchao <jczhang at mcs.anl.gov> wrote:
> 
> 
> On Fri, Oct 19, 2018 at 4:02 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 )
>  
> MUMPS 5.1.2 manual chapter 2.4.2 says it supports "Selective 64-bit integer feature" and "full 64-bit integer version" as well. 

    They use to achieve this by compiling with special Fortran flags to promote integers to 64 bit; this is too fragile for our taste so we never hooked PETSc up wit it. If they have a dependable way of using 64 bit integers we should add that to our mumps.py and test it.

   Barry

> 
> 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/
>