petsc-3.4.2 2013-07-02

# MatTransposeMatMult

Performs Matrix-Matrix Multiplication C=A^T*B.

### Synopsis

    #include "petscmat.h"
    PetscErrorCode  MatTransposeMatMult(Mat A,Mat B,MatReuse scall,PetscReal fill,Mat *C)

Neighbor-wise Collective on Mat

### Input Parameters

| A | - the left matrix
| B | - the right matrix
| scall | - either MAT_INITIAL_MATRIX or MAT_REUSE_MATRIX
| fill | - expected fill as ratio of nnz(C)/(nnz(A) + nnz(B)), use PETSC_DEFAULT if not known

### Output Parameters

C -the product matrix

### Notes

C will be created if MAT_INITIAL_MATRIX and must be destroyed by the user with MatDestroy().

MAT_REUSE_MATRIX can only be used if the matrices A and B have the same nonzero pattern as in the previous call

To determine the correct fill value, run with -info and search for the string "Fill ratio" to see the value actually needed.

This routine is currently implemented for pairs of AIJ matrices and pairs of SeqDense matrices and classes which inherit from SeqAIJ. C will be of same type as the input matrices.

### See Also

MatTransposeMatMultSymbolic(), MatTransposeMatMultNumeric(), MatMatMult(), MatMatTransposeMult(), MatPtAP()

Level:intermediate
Location: src/mat/interface/matrix.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages

### Examples

src/ksp/ksp/examples/tutorials/ex10.c.html