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# MatTranspose

Computes the transpose of a matrix, either in-place or out-of-place.

## Synopsis

    #include "petscmat.h"
    PetscErrorCode MatTranspose(Mat mat, MatReuse reuse, Mat *B)

Collective

## Input Parameters

- mat - the matrix to transpose

- reuse - either `MAT_INITIAL_MATRIX`, `MAT_REUSE_MATRIX`, or `MAT_INPLACE_MATRIX`

## Output Parameter

- B - the transpose of the matrix

## Notes

If you use `MAT_INPLACE_MATRIX` then you must pass in `&mat` for `B`

`MAT_REUSE_MATRIX` uses the `B` matrix obtained from a previous call to this function with `MAT_INITIAL_MATRIX` to store the transpose. If you already have a matrix to contain the transpose, call `MatTransposeSetPrecursor(mat, B)` before calling this routine.

If the nonzero structure of `mat` changed from the previous call to this function with the same matrices an error will be generated for some matrix types.

Consider using `MatCreateTranspose()` instead if you only need a matrix that behaves like the transpose but don’t need the storage to be changed. For example, the result of `MatCreateTranspose()` will compute the transpose of the given matrix times a vector for matrix-vector products computed with `MatMult()`.

If `mat` is unchanged from the last call this function returns immediately without recomputing the result

If you only need the symbolic transpose of a matrix, and not the numerical values, use `MatTransposeSymbolic()`

## See Also

Matrices, `Mat`, `MatTransposeSetPrecursor()`, `MatMultTranspose()`, `MatMultTransposeAdd()`, `MatIsTranspose()`, `MatReuse`, `MAT_INITIAL_MATRIX`, `MAT_REUSE_MATRIX`, `MAT_INPLACE_MATRIX`, `MatTransposeSymbolic()`, `MatCreateTranspose()`

## Level

intermediate

## Location

src/mat/interface/matrix.c

## Examples

src/ksp/ksp/tutorials/ex65.c
src/ksp/pc/tutorials/ex4.c
src/ksp/ksp/tutorials/ex74.c
src/ksp/ksp/tutorials/ex87.c
src/tao/pde_constrained/tutorials/hyperbolic.c
src/tao/pde_constrained/tutorials/parabolic.c
src/ksp/ksp/tutorials/ex43.c
src/snes/tutorials/ex70.c

## Implementations

MatTranspose_MPIAIJ() in src/mat/impls/aij/mpi/mpiaij.c
MatTranspose_SeqAIJKokkos() in src/mat/impls/aij/seq/kokkos/aijkok.kokkos.cxx
MatTranspose_SeqAIJ() in src/mat/impls/aij/seq/symtranspose.c
MatTranspose_MPIBAIJ() in src/mat/impls/baij/mpi/mpibaij.c
MatTranspose_SeqBAIJ() in src/mat/impls/baij/seq/baij.c
MatTranspose_ConstantDiagonal() in src/mat/impls/cdiagonal/cdiagonal.c
MatTranspose_MPIDense() in src/mat/impls/dense/mpi/mpidense.c
MatTranspose_SeqDense() in src/mat/impls/dense/seq/dense.c
MatTranspose_Diagonal() in src/mat/impls/diagonal/diagonal.c
MatTranspose_Elemental() in src/mat/impls/elemental/matelem.cxx
MatTranspose_Htool() in src/mat/impls/htool/htool.cxx
MatTranspose_IS() in src/mat/impls/is/matis.c
MatTranspose_Nest() in src/mat/impls/nest/matnest.c
MatTranspose_MPISBAIJ() in src/mat/impls/sbaij/mpi/mpisbaij.c
MatTranspose_SeqSBAIJ() in src/mat/impls/sbaij/seq/sbaij.c
MatTranspose_ScaLAPACK() in src/mat/impls/scalapack/matscalapack.c

Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages