Dear list, I would like to construct a large, sparse matrix M out of four submatrices.
(A B) (C D) These submatrices are obtained as results of MatMatMult multiplications of other sparse matrices. I have tried the following procedure for all four submatrices (here only for A) Mat A; MatGetLocalSubMatrix(M, rows1, cols1, MAT_INITIAL_MATRIX, &A); MatMatMult(A1, A2, MAT_INITIAL_MATRIX, PETSC_DEFAULT, &A); MatRestoreLocalSubMatrix(M, rows1, cols1, &A); These lines use appropriate ISs rows1 and cols1 which contain the first rows and columns of M that correspond to the submatrix A. This, however results in an empty matrix M. What am I doing wrong? If this is not the right approach, how can I do it better? Manually copying the values from the results of the multiplications into M takes forever, unfortunately.. Thanks for your help! Jan
