[petsc-users] Need to update matrix in every loop

[sheng liu]

Hello:
    I have a large sparse symmetric matrix ( about 1000000x1000000), and I
need about 10 eigenvalues near 0. The problem is: I need to run the same
program about 1000 times, each time I need to change the diagonal matrix
elements ( and they are generated randomly). Is there a fast way to
implement this problem? Thank you!