[petsc-users] Calculate only the diagonal elements for matrix matrix multiplications

[ehsan sadrfaridpour]

Hi,
I need the diagonal elements from result of multiplying matrix A, B
together.
I can get by multiplying the 2 matrices and then call MatGetDiagonal.
However, I only need the values on the diagonal and the rest of the
elements are useless for me.
As the size of matrices increase, I am afraid it affect the performance.

So, I am looking for another method that only calculates the diagonal of
multiplication and not the rest of elements.
If there is not such a method for matrix, how can I use the vector's
operations to reach the same results?


Best,
Ehsan
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