[petsc-users] MAT_NEW_NONZERO_LOCATION_ERR

[Zhang, Hong]

Thibaut :
Sorry, I did not explain it clearly. You call
MatSetOption(A,MAT_NEW_NONZERO_LOCATION_ERR,PETSC_TRUE);
AFTER matrix is assembled. Then no more new zero is allowed to add/insert. For example, I add following in
petsc/src/ksp/ksp/examples/tutorials/ex1.c:

   ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
   ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

+  ierr = MatSetOption(A,MAT_NEW_NONZERO_LOCATION_ERR,PETSC_TRUE);CHKERRQ(ierr);
+  i    = 0; col[0] = 2;
+  ierr = MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);CHKERRQ(ierr);
+  ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
+  ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
+
Then the code crashes with
0]PETSC ERROR: Argument out of range
[0]PETSC ERROR: Inserting a new nonzero at (0,2) in the matrix.

Adding entries to the tridiagonal works.
Hong

Well, try and create a small SEQAIJ/MPIAIJ matrix and preallocate memory for the diagonal.

When I try to call MatSetValues to fill the diagonal, on the first row I get

[0]PETSC ERROR: Argument out of range
[0]PETSC ERROR: Inserting a new nonzero at (0,0) in the matrix

Which is within my preallocated non-zero structure.

This is why I'm confused.

Thibaut


On 08/10/2019 15:31, Zhang, Hong wrote:
Thibaut:
Hi,

Just out of curiosity, I'm a bit confused by the parameter option
MAT_NEW_NONZERO_LOCATION_ERR.

It triggers an error if you try to insert/add a value in the non-zero
structure, regardless of the matrix preallocation status. In what case
would such an option be useful?

 It triggers an error if you try to insert/add a NEW value outside of your preallocated non-zero structure.
Hong

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