:orphan:
# DMSetMatrixPreallocateOnly
When `DMCreateMatrix()` is called the matrix will be properly preallocated but the nonzero structure and zero values will not be set. 
## Synopsis
```
#include "petscdm.h"          
#include "petscdmlabel.h"     
#include "petscds.h"     
PetscErrorCode DMSetMatrixPreallocateOnly(DM dm, PetscBool only)
```
Logically Collective


## Input Parameters

- ***dm -*** the `DM`
- ***only -*** `PETSC_TRUE` if only want preallocation



## Options Database Key

- ***-dm_preallocate_only -*** Only preallocate the matrix for `DMCreateMatrix()`, `DMCreateMassMatrix()`, but do not fill it with zeros





## See Also
 [](ch_dmbase), `DM`, `DMCreateMatrix()`, `DMCreateMassMatrix()`, `DMSetMatrixStructureOnly()`, `DMSetMatrixPreallocateSkip()`

## Level
developer

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/interface/dm.c.html#DMSetMatrixPreallocateOnly">src/dm/interface/dm.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/stag/tutorials/ex8.c.html">src/dm/impls/stag/tutorials/ex8.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/burgers_spectral.c.html">src/tao/unconstrained/tutorials/burgers_spectral.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/spectraladjointassimilation.c.html">src/tao/unconstrained/tutorials/spectraladjointassimilation.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/tutorials/ex50.c.html">src/ts/tutorials/ex50.c</A><BR>


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