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# PCHPDDMSetDeflationMat
Sets the deflation space used to assemble a coarser operator.
## Synopsis
```
#include "petscpc.h"
PetscErrorCode PCHPDDMSetDeflationMat(PC pc, IS is, Mat U)
```
## Input Parameters
- ***pc -*** preconditioner context
- ***is -*** index set of the local deflation matrix
- ***U -*** deflation sequential matrix stored as a `MATSEQDENSE`
## See Also
`PCHPDDM`, `PCDeflationSetSpace()`, `PCMGSetRestriction()`
## Level
advanced
## Location
src/ksp/pc/impls/hpddm/pchpddm.cxx
## Implementations
PCHPDDMSetDeflationMat_HPDDM in src/ksp/pc/impls/hpddm/pchpddm.cxx
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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ksp/pc/impls/hpddm/pchpddm.cxx)
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