:orphan:
# MatSetValue
Set a single entry into a matrix. This value may be cached, so `MatAssemblyBegin()` and `MatAssemblyEnd()`
MUST be called after all calls to `MatSetValue()` have been completed.


## Synopsis
```
#include <petscmat.h>
PetscErrorCode MatSetValue(Mat m,PetscInt i,PetscInt j,PetscScalar va,InsertMode mode)
```
Not Collective


## Input Parameters

- ***m -*** the matrix
- ***i -*** the row location of the entry
- ***j -*** the column location of the entry
- ***va -*** the value to insert
- ***mode -*** either `INSERT_VALUES` or `ADD_VALUES`





## Note
For efficiency one should use `MatSetValues()` and set several values simultaneously.


## See Also
 [](ch_matrices), `Mat`, `MatAssemblyBegin()`, `MatAssemblyEnd`, `InsertMode`, `MatGetValue()`, `MatSetValues()`,
`MatSetValueLocal()`, `MatSetValuesLocal()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscmat.h.html#MatSetValue">include/petscmat.h</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex21.c.html">src/ksp/ksp/tutorials/ex21.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex27.c.html">src/ksp/ksp/tutorials/ex27.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex4.c.html">src/ksp/ksp/tutorials/ex4.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex44f.F90.html">src/ksp/ksp/tutorials/ex44f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex59.c.html">src/ksp/ksp/tutorials/ex59.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex61f.F90.html">src/ksp/ksp/tutorials/ex61f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex73.c.html">src/ksp/ksp/tutorials/ex73.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex76.c.html">src/ksp/ksp/tutorials/ex76.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/tutorials/ex4.c.html">src/mat/tutorials/ex4.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/tutorials/ex4f.F90.html">src/mat/tutorials/ex4f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex47cu.cu.html">src/snes/tutorials/ex47cu.cu</A><BR>


---
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