:orphan:
# DMCreateMassMatrix
Gets the mass matrix between two `DM` objects, M_ij = \int \phi_i \psi_j where the \phi are Galerkin basis functions for a a Galerkin finite element model on the `DM` 
## Synopsis
```
#include "petscdm.h"          
#include "petscdmlabel.h"     
#include "petscds.h"     
PetscErrorCode DMCreateMassMatrix(DM dmc, DM dmf, Mat *mat)
```
Collective


## Input Parameters

- ***dmc -*** the target `DM` object
- ***dmf -*** the source `DM` object



## Output Parameter

- ***mat -*** the mass matrix





## Notes
For `DMPLEX` the finite element model for the `DM` must have been already provided.

if `dmc` is `dmf` then x^t M x is an approximation to the L2 norm of the vector x which is obtained by `DMCreateGlobalVector()`


## See Also
 [](ch_dmbase), `DM`, `DMCreateMassMatrixLumped()`, `DMCreateMatrix()`, `DMCreateMassMatrix()`, `DMRefine()`, `DMCoarsen()`, `DMCreateRestriction()`, `DMCreateInterpolation()`, `DMCreateInjection()`

## Level
developer

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

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/swarm/tutorials/ex1.c.html">src/dm/impls/swarm/tutorials/ex1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/swarm/tutorials/ex1f90.F90.html">src/dm/impls/swarm/tutorials/ex1f90.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex36.c.html">src/snes/tutorials/ex36.c</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/plex.c.html#DMCreateMassMatrix_Plex">DMCreateMassMatrix_Plex in src/dm/impls/plex/plex.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/swarm/swarm.c.html#DMCreateMassMatrix_Swarm">DMCreateMassMatrix_Swarm in src/dm/impls/swarm/swarm.c</A><BR>


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