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# MatSetPreallocationCOO

set preallocation for matrices using a coordinate format of the entries with global indices

## Synopsis

    #include "petscmat.h"
    PetscErrorCode MatSetPreallocationCOO(Mat A, PetscCount ncoo, PetscInt coo_i[], PetscInt coo_j[])

Collective

## Input Parameters

- A - matrix being preallocated

- ncoo - number of entries

- coo_i - row indices

- coo_j - column indices

## Notes

The indices within `coo_i` and `coo_j` may be modified within this function. The caller should not rely on them having any specific value after this function returns. The arrays can be freed or reused immediately after this function returns.

Entries can be repeated, see `MatSetValuesCOO()`. Entries with negative row or column indices are allowed but will be ignored. The corresponding entries in `MatSetValuesCOO()` will be ignored too. Remote entries are allowed and will be properly added or inserted to the matrix, unless the matrix option `MAT_IGNORE_OFF_PROC_ENTRIES` is set, in which case remote entries are ignored, or `MAT_NO_OFF_PROC_ENTRIES` is set, in which case an error will be generated.

If you just want to create a sequential AIJ matrix (`MATSEQAIJ`), and your matrix entries in COO format are unique, you can also use `MatCreateSeqAIJFromTriple()`. But that is not recommended for iterative applications.

## See Also

Matrices, `Mat`, `MatSetValuesCOO()`, `MatSeqAIJSetPreallocation()`, `MatMPIAIJSetPreallocation()`, `MatSeqBAIJSetPreallocation()`, `MatMPIBAIJSetPreallocation()`, `MatSeqSBAIJSetPreallocation()`, `MatMPISBAIJSetPreallocation()`, `MatSetPreallocationCOOLocal()`, `DMSetMatrixPreallocateSkip()`, `MatCreateSeqAIJFromTriple()`

## Level

beginner

## Location

src/mat/utils/gcreate.c

## Examples

src/ksp/ksp/tutorials/ex88f.F90
src/ksp/ksp/tutorials/ex83f.F90
src/ksp/ksp/tutorials/bench_kspsolve.c
src/mat/tutorials/ex18.c
src/snes/tutorials/ex55k.kokkos.cxx

## Implementations

MatSetPreallocationCOO_MPIAIJKokkos() in src/mat/impls/aij/mpi/kokkos/mpiaijkok.kokkos.cxx
MatSetPreallocationCOO_MPIAIJ() in src/mat/impls/aij/mpi/mpiaij.c
MatSetPreallocationCOO_MPIAIJCUSPARSE() in src/mat/impls/aij/mpi/mpicusparse/mpiaijcusparse.cu
MatSetPreallocationCOO_MPIAIJHIPSPARSE() in src/mat/impls/aij/mpi/mpihipsparse/mpiaijhipsparse.hip.c
MatSetPreallocationCOO_SeqAIJ() in src/mat/impls/aij/seq/aij.c
MatSetPreallocationCOO_SeqAIJKokkos() in src/mat/impls/aij/seq/kokkos/aijkok.kokkos.cxx
MatSetPreallocationCOO_SeqAIJCUSPARSE() in src/mat/impls/aij/seq/seqcusparse/aijcusparse.cu
MatSetPreallocationCOO_SeqAIJHIPSPARSE() in src/mat/impls/aij/seq/seqhipsparse/aijhipsparse.hip.c
MatSetPreallocationCOO_HYPRE() in src/mat/impls/hypre/mhypre.c
MatSetPreallocationCOO_IS() in src/mat/impls/is/matis.c

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Index of all manual pages