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# PetscLayout
defines layout of vectors and matrices (that is the "global" numbering of vector and matrix entries) across MPI processes (which rows are owned by which processes) 
## Synopsis
```
typedef struct _n_PetscLayout *PetscLayout;
```



## Notes
PETSc vectors (`Vec`) have a global number associated with each vector entry. The first MPI process that shares the vector owns the first `n0` entries of the vector,
the second MPI process the next `n1` entries, etc. A `PetscLayout` is a way of managing this information, for example the number of locally owned entries is provided
by `PetscLayoutGetLocalSize()` and the range of indices for a given MPI process is provided by `PetscLayoutGetRange()`.

Each PETSc `Vec` contains a `PetscLayout` object which can be obtained with `VecGetLayout()`. For convenience `Vec` provides an API to access the layout information directly,
for example with `VecGetLocalSize()` and `VecGetOwnershipRange()`.

Similarly PETSc matrices have layouts, these are discussed in [](ch_matrices).


## See Also
 `PetscLayoutCreate()`, `PetscLayoutDestroy()`, `PetscLayoutGetRange()`, `PetscLayoutGetLocalSize()`, `PetscLayoutGetSize()`,
`PetscLayoutGetBlockSize()`, `PetscLayoutGetRanges()`, `PetscLayoutFindOwner()`,  `PetscLayoutFindOwnerIndex()`,
`VecGetLayout()`, `VecGetLocalSize()`, `VecGetOwnershipRange()`

## Level
developer

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscistypes.h.html#PetscLayout">include/petscistypes.h</A>


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