[petsc-users] MatGetRow_MPIAIJ error

[Jose E. Roman]

Mat objects in PETSc are parallel, meaning that the data structure is distributed. You should use MatGetOwnershipRange() so that each process accesses its local rows only. https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetOwnershipRange.html

This is very basic usage. You should read the manual and the online documentation including examples, and try hard to solve these issues before asking to the list.

Jose

> El 20 mar 2019, a las 8:52, Eda Oktay via petsc-users <petsc-users at mcs.anl.gov> escribió:
> 
> Hello,
> 
> I wrote a code computing element wise absolute value of a matrix. When I run the code sequentially, it works. However, when I try to use it in parallel with the same matrix, I get the following error:
> 
> [1]PETSC ERROR: Argument out of range
> [1]PETSC ERROR: Only local rows
> 
> The absolute value code is:
> 
> ierr = MatGetSize(A,&n,NULL);CHKERRQ(ierr);
> ierr = MatDuplicate(A,MAT_COPY_VALUES,AbsA);CHKERRQ(ierr);
>   
>   for (i=0; i<n; i++) {
>     ierr = MatGetRow(A,i,&nc,&aj,&aa);CHKERRQ(ierr);                               
> 
>     PetscMalloc1(nc,&absaa);
>     for (j=0; j<nc; j++){
>         absaa[j] = fabs(aa[j]);
>     }
>     
>     ierr = MatSetValues(*AbsA,1,&i,nc,aj,absaa,INSERT_VALUES);CHKERRQ(ierr);    
> ierr = MatRestoreRow(A,i,&nc,&aj,&aa);CHKERRQ(ierr);
>   }
> 
> I didn't understand how I fix this problem since I am new to PETSc.
> 
> Thanks
> 
> Eda