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# MatMatMatMult
Performs matrix-matrix-matrix multiplication D=A*B*C. 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatMatMatMult(Mat A, Mat B, Mat C, MatReuse scall, PetscReal fill, Mat *D)
```
Neighbor-wise Collective


## Input Parameters

- ***A -*** the left matrix
- ***B -*** the middle matrix
- ***C -*** the right matrix
- ***scall -*** either `MAT_INITIAL_MATRIX` or `MAT_REUSE_MATRIX`
- ***fill -*** expected fill as ratio of nnz(D)/(nnz(A) + nnz(B)+nnz(C)), use `PETSC_DEFAULT` if you do not have a good estimate
if the result is a dense matrix this is irrelevant



## Output Parameter

- ***D -*** the product matrix





## Notes
Unless scall is `MAT_REUSE_MATRIX` D will be created.

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

This routine is shorthand for using `MatProductCreate()` with the `MatProductType` of `MATPRODUCT_ABC`

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

If you have many matrices with the same non-zero structure to multiply, you
should use `MAT_REUSE_MATRIX` in all calls but the first


## See Also
 [](ch_matrices), `Mat`, `MatProductCreate()`, `MATPRODUCT_ABC`, `MatMatMult`, `MatPtAP()`, `MatMatTransposeMult()`, `MatTransposeMatMult()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/interface/matrix.c.html#MatMatMatMult">src/mat/interface/matrix.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/mat/interface/matrix.c)


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