[petsc-users] Large MATMPIAIJ - 32bit integer overflow in nz value

[Matthew Knepley]

On Wed, May 17, 2023 at 9:02 AM Fleischli Benno HSLU T&A <
benno.fleischli at hslu.ch> wrote:

> Dear PETSc developers
>
> I am creating a very large parallel sparse matrix (MATMPIAIJ) with PETSc.
> I write this matrix to disk.
> The number of non-zeros exceeds the maximum number a 32-bit integer can
> hold.
> When I read the matrix from disk i get an error because there was an
> overflow in the nz number.
> (see petsc-3.18.4/src/mat/impls/aij/seq/aij.c:4977)
>
> Obviously I could compile PETSc with 64bit integers
> (--with-64-bit-indices).
> But I wanted to ask if there is another way. Because the total number of
> nonzeros nz is the only numer that exceeds the 32bit limit.
> It would not be efficient to use 64bit integers everywhere just because of
> this single number.
>

Integers tend to be a small part of the overall storage. How much does it
increase the maximum overall storage for your problem?

  Thanks,

     Matt


> This how I configured PETSc:
>
> ./configure --download-fblaslapack --download-hpddm --download-hypre
> --with-debugging=0
> COPTFLAGS='-O3 -march=native -mtune=native' CXXOPTFLAGS='-O3 -march=native
> -mtune=native'
> FOPTFLAGS='-O3 -march=native -mtune=native' --with-scalar-type=real
> (--with-mpi-dir=/home/benno/Libraries/openMPI)
>
>
>
> Kind Regards
>
> Benno
>
>
>
> ________________________________
>
>
> *Hochschule Luzern Technik & Architektur*
> Institute for Mechanical Engineering and Energy Technology
>
> Competence Center Fluid Mechanics and Numerical Methods
>
>
> *Benno Fleischli*
> MSc in Mechanical Engineering / BSc in Electrical Engineering
>
> Wissenschaftlicher Mitarbeiter
>
> benno.fleischli at hslu.ch
> <https://webmail.hslu.ch/owa/redir.aspx?C=rM5K5xPd_kKJmyojcJXaG18BaXM9wM8IqSslYJQen5H6HtdiNS2KtWNFL89yfRdRtW-Oa6xCXTk.&URL=mailto%3akatrina.kemp%40hslu.ch>
>
>

-- 
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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