[petsc-users] Problem with MatMPIAIJSetPreallocation

[Matthew Thomas]

Hello,



When I use MatMPIAIJSetPreallocation I get an argument out of range error, as below,



[15]PETSC ERROR: Argument out of range

[15]PETSC ERROR: New nonzero at (8,421) caused a malloc. Use MatSetOption(A, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE) to turn off this check



However, when I run the code again with identical parameters without MatMPIAIJSetPreallocation, there is no non-zero at the location that caused the error (8, 421). Using -mat_view I can see that row 8 only contains a single value at column 8, which is expected and what I have allocated for.


I have also checked that every time I call MatSetValues that this location is not being set.


I am very confident my dnnz and onnz arrays have been set correctly, do you have any idea why this new non-zero is created?


I am using Petsc version 3.22.1 and Slepc version 3.22.1 with fortran.


This issue does not occur with small number of processors, (1-8), however, this error is consistent when I use >8 processors.


Thanks,

Matt
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