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# MATCOMPOSITE
A matrix defined by the sum (or product) of one or more matrices. The matrices need to have a correct size and parallel layout for the sum or product to be valid. 


## Note
To use the product of the matrices call `MatCompositeSetType`(mat,`MAT_COMPOSITE_MULTIPLICATIVE`);


## See Also
 [](ch_matrices), `Mat`, `MatCreateComposite()`, `MatCompositeSetScalings()`, `MatCompositeAddMat()`, `MatSetType()`, `MatCompositeSetType()`, `MatCompositeGetType()`,
`MatCompositeSetMatStructure()`, `MatCompositeGetMatStructure()`, `MatCompositeMerge()`, `MatCompositeSetMergeType()`, `MatCompositeGetNumberMat()`, `MatCompositeGetMat()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/composite/mcomposite.c.html#MATCOMPOSITE">src/mat/impls/composite/mcomposite.c</A>


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


[Index of all Mat routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)