# MatMultTranspose
Computes matrix transpose times a vector y = A^T * x. 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatMultTranspose(Mat mat, Vec x, Vec y)
```
Neighbor-wise Collective


## Input Parameters

- ***mat -*** the matrix
- ***x   -*** the vector to be multiplied



## Output Parameters

- ***y -*** the result





## Notes
The vectors `x` and `y` cannot be the same.  I.e., one cannot
call `MatMultTranspose`(A,y,y).

For complex numbers this does NOT compute the Hermitian (complex conjugate) transpose multiple,
use `MatMultHermitianTranspose()`


## See Also
 `Mat`, `MatMult()`, `MatMultAdd()`, `MatMultTransposeAdd()`, `MatMultHermitianTranspose()`, `MatTranspose()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/interface/matrix.c.html#MatMultTranspose">src/mat/interface/matrix.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/tutorials/ex2.c.html">src/mat/tutorials/ex2.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/swarm/tutorials/ex1.c.html">src/dm/impls/swarm/tutorials/ex1.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/swarm/tutorials/ex1f90.F90.html">src/dm/impls/swarm/tutorials/ex1f90.F90.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex53.c.html">src/ksp/ksp/tutorials/ex53.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex72.c.html">src/ksp/ksp/tutorials/ex72.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex73.c.html">src/ksp/ksp/tutorials/ex73.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex36.c.html">src/snes/tutorials/ex36.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/constrained/tutorials/tomographyADMM.c.html">src/tao/constrained/tutorials/tomographyADMM.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/pde_constrained/tutorials/elliptic.c.html">src/tao/pde_constrained/tutorials/elliptic.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/pde_constrained/tutorials/hyperbolic.c.html">src/tao/pde_constrained/tutorials/hyperbolic.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/tutorials/ex4.c.html">src/tao/tutorials/ex4.c.html</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/da/usfft/matusfft.c.html#MatMultTranspose_SeqUSFFT">MatMultTranspose_SeqUSFFT in src/dm/impls/da/usfft/matusfft.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/h2opus/pch2opus.c.html#MatMultTranspose_MAmI">MatMultTranspose_MAmI in src/ksp/pc/impls/h2opus/pch2opus.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/h2opus/pch2opus.c.html#MatMultTranspose_Hyper">MatMultTranspose_Hyper in src/ksp/pc/impls/h2opus/pch2opus.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/h2opus/pch2opus.c.html#MatMultTranspose_NS">MatMultTranspose_NS in src/ksp/pc/impls/h2opus/pch2opus.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/mpi/kokkos/mpiaijkok.kokkos.cxx.html#MatMultTranspose_MPIAIJKokkos">MatMultTranspose_MPIAIJKokkos in src/mat/impls/aij/mpi/kokkos/mpiaijkok.kokkos.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/mpi/mpiaij.c.html#MatMultTranspose_MPIAIJ">MatMultTranspose_MPIAIJ in src/mat/impls/aij/mpi/mpiaij.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/mpi/mpicusparse/mpiaijcusparse.cu.html#MatMultTranspose_MPIAIJCUSPARSE">MatMultTranspose_MPIAIJCUSPARSE in src/mat/impls/aij/mpi/mpicusparse/mpiaijcusparse.cu</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/mpi/mpihipsparse/mpiaijhipsparse.hip.c.html#MatMultTranspose_MPIAIJHIPSPARSE">MatMultTranspose_MPIAIJHIPSPARSE in src/mat/impls/aij/mpi/mpihipsparse/mpiaijhipsparse.hip.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/aij.c.html#MatMultTranspose_SeqAIJ">MatMultTranspose_SeqAIJ in src/mat/impls/aij/seq/aij.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/aijmkl/aijmkl.c.html#MatMultTranspose_SeqAIJMKL">MatMultTranspose_SeqAIJMKL in src/mat/impls/aij/seq/aijmkl/aijmkl.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/aijsell/aijsell.c.html#MatMultTranspose_SeqAIJSELL">MatMultTranspose_SeqAIJSELL in src/mat/impls/aij/seq/aijsell/aijsell.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/kokkos/aijkok.kokkos.cxx.html#MatMultTranspose_SeqAIJKokkos">MatMultTranspose_SeqAIJKokkos in src/mat/impls/aij/seq/kokkos/aijkok.kokkos.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/seqcusparse/aijcusparse.cu.html#MatMultTranspose_SeqAIJCUSPARSE">MatMultTranspose_SeqAIJCUSPARSE in src/mat/impls/aij/seq/seqcusparse/aijcusparse.cu</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/seqhipsparse/aijhipsparse.hip.c.html#MatMultTranspose_SeqAIJHIPSPARSE">MatMultTranspose_SeqAIJHIPSPARSE in src/mat/impls/aij/seq/seqhipsparse/aijhipsparse.hip.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/baij/mpi/mpibaij.c.html#MatMultTranspose_MPIBAIJ">MatMultTranspose_MPIBAIJ in src/mat/impls/baij/mpi/mpibaij.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/baij/seq/baij2.c.html#MatMultTranspose_SeqBAIJ">MatMultTranspose_SeqBAIJ in src/mat/impls/baij/seq/baij2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/blockmat/seq/blockmat.c.html#MatMultTranspose_BlockMat">MatMultTranspose_BlockMat in src/mat/impls/blockmat/seq/blockmat.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/cdiagonal/cdiagonal.c.html#MatMultTranspose_ConstantDiagonal">MatMultTranspose_ConstantDiagonal in src/mat/impls/cdiagonal/cdiagonal.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/composite/mcomposite.c.html#MatMultTranspose_Composite">MatMultTranspose_Composite in src/mat/impls/composite/mcomposite.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/cufft/cufft.cu.html#MatMultTranspose_SeqCUFFT">MatMultTranspose_SeqCUFFT in src/mat/impls/cufft/cufft.cu</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/mpi/mpidense.c.html#MatMultTranspose_MPIDense">MatMultTranspose_MPIDense in src/mat/impls/dense/mpi/mpidense.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/seq/cuda/densecuda.cu.html#MatMultTranspose_SeqDenseCUDA">MatMultTranspose_SeqDenseCUDA in src/mat/impls/dense/seq/cuda/densecuda.cu</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/seq/dense.c.html#MatMultTranspose_SeqDense">MatMultTranspose_SeqDense in src/mat/impls/dense/seq/dense.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/seq/hip/densehip.hip.c.html#MatMultTranspose_SeqDenseHIP">MatMultTranspose_SeqDenseHIP in src/mat/impls/dense/seq/hip/densehip.hip.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/elemental/matelem.cxx.html#MatMultTranspose_Elemental">MatMultTranspose_Elemental in src/mat/impls/elemental/matelem.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/fft/fftw/fftw.c.html#MatMultTranspose_SeqFFTW">MatMultTranspose_SeqFFTW in src/mat/impls/fft/fftw/fftw.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/fft/fftw/fftw.c.html#MatMultTranspose_MPIFFTW">MatMultTranspose_MPIFFTW in src/mat/impls/fft/fftw/fftw.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/h2opus/cuda/math2opus.cu.html#MatMultTranspose_H2OPUS">MatMultTranspose_H2OPUS in src/mat/impls/h2opus/cuda/math2opus.cu</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/htool/htool.cxx.html#MatMultTranspose_Htool">MatMultTranspose_Htool in src/mat/impls/htool/htool.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/hypre/mhypre.c.html#MatMultTranspose_HYPRE">MatMultTranspose_HYPRE in src/mat/impls/hypre/mhypre.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/is/matis.c.html#MatMultTranspose_IS">MatMultTranspose_IS in src/mat/impls/is/matis.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/lrc/lrc.c.html#MatMultTranspose_LRC">MatMultTranspose_LRC in src/mat/impls/lrc/lrc.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/nest/matnest.c.html#MatMultTranspose_Nest">MatMultTranspose_Nest in src/mat/impls/nest/matnest.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/normal/normm.c.html#MatMultTranspose_Normal">MatMultTranspose_Normal in src/mat/impls/normal/normm.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/scalapack/matscalapack.c.html#MatMultTranspose_ScaLAPACK">MatMultTranspose_ScaLAPACK in src/mat/impls/scalapack/matscalapack.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/scatter/mscatter.c.html#MatMultTranspose_Scatter">MatMultTranspose_Scatter in src/mat/impls/scatter/mscatter.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/sell/mpi/mpisell.c.html#MatMultTranspose_MPISELL">MatMultTranspose_MPISELL in src/mat/impls/sell/mpi/mpisell.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/sell/seq/sell.c.html#MatMultTranspose_SeqSELL">MatMultTranspose_SeqSELL in src/mat/impls/sell/seq/sell.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/shell/shell.c.html#MatMultTranspose_Shell">MatMultTranspose_Shell in src/mat/impls/shell/shell.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/shell/shellcnv.c.html#MatMultTranspose_CF">MatMultTranspose_CF in src/mat/impls/shell/shellcnv.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/submat/submat.c.html#MatMultTranspose_SubMatrix">MatMultTranspose_SubMatrix in src/mat/impls/submat/submat.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/transpose/transm.c.html#MatMultTranspose_Transpose">MatMultTranspose_Transpose in src/mat/impls/transpose/transm.c</A><BR>


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


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