[petsc-users] Memory usage scaling with number of processors

[Matthew Thomas via petsc-users]

Hello, I am using petsc and slepc to solve an eigenvalue problem for sparse matrices. When I run my code with double the number of processors, the memory usage also doubles. I am able to reproduce this behaviour with ex1 of slepc’s hands on

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Hello,

I am using petsc and slepc to solve an eigenvalue problem for sparse matrices. When I run my code with double the number of processors, the memory usage also doubles.

I am able to reproduce this behaviour with ex1 of slepc’s hands on exercises.

The issue is occurring with petsc not with slepc as this still occurs when I remove the solve step and just create and assemble the petsc matrix.

With n=100000, this uses ~1Gb with 8 processors, but ~5Gb with 40 processors. 

This was done with petsc 3.21.3, on linux compiled with Intel using Intel-MPI

Is this the expected behaviour? If not, how can I bug fix this?


Thanks,
Matt