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# MatCreateSeqAIJ
Creates a sparse matrix in `MATSEQAIJ` (compressed row) format (the default parallel PETSc format).  For good matrix assembly performance the user should preallocate the matrix storage by setting the parameter `nz` (or the array `nnz`). 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatCreateSeqAIJ(MPI_Comm comm, PetscInt m, PetscInt n, PetscInt nz, const PetscInt nnz[], Mat *A)
```
Collective


## Input Parameters

- ***comm -*** MPI communicator, set to `PETSC_COMM_SELF`
- ***m -*** number of rows
- ***n -*** number of columns
- ***nz -*** number of nonzeros per row (same for all rows)
- ***nnz -*** array containing the number of nonzeros in the various rows
(possibly different for each row) or NULL



## Output Parameter

- ***A -*** the matrix



## Options Database Keys

- ***-mat_no_inode  -*** Do not use inodes
- ***-mat_inode_limit <limit> -*** Sets inode limit (max limit=5)





## Notes
If `nnz` is given then `nz` is ignored

The `MATSEQAIJ` format, also called
compressed row storage, is fully compatible with standard Fortran
storage.  That is, the stored row and column indices can begin at
either one (as in Fortran) or zero.

Specify the preallocated storage with either `nz` or `nnz` (not both).
Set `nz` = `PETSC_DEFAULT` and `nnz` = `NULL` for PETSc to control dynamic memory
allocation.

By default, this format uses inodes (identical nodes) when possible, to
improve numerical efficiency of matrix-vector products and solves. We
search for consecutive rows with the same nonzero structure, thereby
reusing matrix information to achieve increased efficiency.


## See Also
 [](ch_matrices), `Mat`, [Sparse Matrix Creation](sec_matsparse), `MatCreate()`, `MatCreateAIJ()`, `MatSetValues()`, `MatSeqAIJSetColumnIndices()`, `MatCreateSeqAIJWithArrays()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/aij.c.html#MatCreateSeqAIJ">src/mat/impls/aij/seq/aij.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex13.c.html">src/ksp/ksp/tutorials/ex13.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex13f90.F90.html">src/ksp/ksp/tutorials/ex13f90.F90</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/ex76.c.html">src/ksp/ksp/tutorials/ex76.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/tutorials/ex1.c.html">src/ksp/pc/tutorials/ex1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/tutorials/ex2.c.html">src/ksp/pc/tutorials/ex2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/tutorials/ex12.c.html">src/mat/tutorials/ex12.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex59.c.html">src/snes/tutorials/ex59.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/complementarity/tutorials/minsurf1.c.html">src/tao/complementarity/tutorials/minsurf1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/eptorsion1.c.html">src/tao/unconstrained/tutorials/eptorsion1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/eptorsion3.c.html">src/tao/unconstrained/tutorials/eptorsion3.c</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/mat/impls/aij/seq/aij.c)


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