[petsc-users] Off-diagonal matrix-vector product y=(A-diag(A))x

[Ingo Gaertner]

Does PETSc include an efficient implementation for the operation
y=(A-diag(A))x or y_i=\sum_{j!=i}A_{ij}x_j on a sparse matrix A?

In words, I need a matrix-vector product after the matrix diagonal has been
set to zero. For efficiency reasons I can't copy and modify the matrix or
first calculate the full product and then subtract the diagonal
contribution.

Thanks
Ingo
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