#include "petscmat.h" PetscErrorCode MatCreateSubMatrix(Mat mat,IS isrow,IS iscol,MatReuse cll,Mat *newmat)Collective on Mat
| mat | - the original matrix | |
| isrow | - parallel IS containing the rows this processor should obtain | |
| iscol | - parallel IS containing all columns you wish to keep. Each process should list the columns that will be in IT's "diagonal part" in the new matrix. | |
| cll | - either MAT_INITIAL_MATRIX or MAT_REUSE_MATRIX |
| newmat | - the new submatrix, of the same type as the old |
Some matrix types place restrictions on the row and column indices, such as that they be sorted or that they be equal to each other.
The index sets may not have duplicate entries.
The first time this is called you should use a cll of MAT_INITIAL_MATRIX, the MatCreateSubMatrix() routine will create the newmat for you. Any additional calls to this routine with a mat of the same nonzero structure and with a call of MAT_REUSE_MATRIX will reuse the matrix generated the first time. You should call MatDestroy() on newmat when you are finished using it.
The communicator of the newly obtained matrix is ALWAYS the same as the communicator of the input matrix.
If iscol is NULL then all columns are obtained (not supported in Fortran).
1 2 0 | 0 3 0 | 0 4
Proc0 0 5 6 | 7 0 0 | 8 0
9 0 10 | 11 0 0 | 12 0
-------------------------------------
13 0 14 | 15 16 17 | 0 0
Proc1 0 18 0 | 19 20 21 | 0 0
0 0 0 | 22 23 0 | 24 0
-------------------------------------
Proc2 25 26 27 | 0 0 28 | 29 0
30 0 0 | 31 32 33 | 0 34
Suppose isrow = [0 1 | 4 | 6 7] and iscol = [1 2 | 3 4 5 | 6]. The resulting submatrix is
2 0 | 0 3 0 | 0
Proc0 5 6 | 7 0 0 | 8
-------------------------------
Proc1 18 0 | 19 20 21 | 0
-------------------------------
Proc2 26 27 | 0 0 28 | 29
0 0 | 31 32 33 | 0