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# 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 Parameter
- ***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
[](ch_matrices), `Mat`, `MatMult()`, `MatMultAdd()`, `MatMultTransposeAdd()`, `MatMultHermitianTranspose()`, `MatTranspose()`
## Level
beginner
## Location
src/mat/interface/matrix.c
## Examples
src/dm/impls/swarm/tutorials/ex1.c
src/dm/impls/swarm/tutorials/ex1f90.F90
src/ksp/ksp/tutorials/ex53.c
src/ksp/ksp/tutorials/ex72.c
src/ksp/ksp/tutorials/ex73.c
src/mat/tutorials/ex2.c
src/snes/tutorials/ex36.c
src/tao/constrained/tutorials/tomographyADMM.c
src/tao/pde_constrained/tutorials/elliptic.c
src/tao/pde_constrained/tutorials/hyperbolic.c
src/tao/tutorials/ex4.c
## Implementations
MatMultTranspose_SeqUSFFT in src/dm/impls/da/usfft/matusfft.c
MatMultTranspose_MAmI in src/ksp/pc/impls/h2opus/pch2opus.c
MatMultTranspose_Hyper in src/ksp/pc/impls/h2opus/pch2opus.c
MatMultTranspose_NS in src/ksp/pc/impls/h2opus/pch2opus.c
MatMultTranspose_MPIAIJKokkos in src/mat/impls/aij/mpi/kokkos/mpiaijkok.kokkos.cxx
MatMultTranspose_MPIAIJ in src/mat/impls/aij/mpi/mpiaij.c
MatMultTranspose_MPIAIJCUSPARSE in src/mat/impls/aij/mpi/mpicusparse/mpiaijcusparse.cu
MatMultTranspose_MPIAIJHIPSPARSE in src/mat/impls/aij/mpi/mpihipsparse/mpiaijhipsparse.hip.c
MatMultTranspose_SeqAIJ in src/mat/impls/aij/seq/aij.c
MatMultTranspose_SeqAIJMKL in src/mat/impls/aij/seq/aijmkl/aijmkl.c
MatMultTranspose_SeqAIJSELL in src/mat/impls/aij/seq/aijsell/aijsell.c
MatMultTranspose_SeqAIJKokkos in src/mat/impls/aij/seq/kokkos/aijkok.kokkos.cxx
MatMultTranspose_SeqAIJCUSPARSE in src/mat/impls/aij/seq/seqcusparse/aijcusparse.cu
MatMultTranspose_SeqAIJHIPSPARSE in src/mat/impls/aij/seq/seqhipsparse/aijhipsparse.hip.c
MatMultTranspose_MPIBAIJ in src/mat/impls/baij/mpi/mpibaij.c
MatMultTranspose_SeqBAIJ in src/mat/impls/baij/seq/baij2.c
MatMultTranspose_BlockMat in src/mat/impls/blockmat/seq/blockmat.c
MatMultTranspose_ConstantDiagonal in src/mat/impls/cdiagonal/cdiagonal.c
MatMultTranspose_Composite in src/mat/impls/composite/mcomposite.c
MatMultTranspose_SeqCUFFT in src/mat/impls/cufft/cufft.cu
MatMultTranspose_MPIDense in src/mat/impls/dense/mpi/mpidense.c
MatMultTranspose_SeqDense in src/mat/impls/dense/seq/dense.c
MatMultTranspose_Elemental in src/mat/impls/elemental/matelem.cxx
MatMultTranspose_SeqFFTW in src/mat/impls/fft/fftw/fftw.c
MatMultTranspose_MPIFFTW in src/mat/impls/fft/fftw/fftw.c
MatMultTranspose_H2OPUS in src/mat/impls/h2opus/cuda/math2opus.cu
MatMultTranspose_Htool in src/mat/impls/htool/htool.cxx
MatMultTranspose_HYPRE in src/mat/impls/hypre/mhypre.c
MatMultTranspose_IS in src/mat/impls/is/matis.c
MatMultTranspose_LRC in src/mat/impls/lrc/lrc.c
MatMultTranspose_Nest in src/mat/impls/nest/matnest.c
MatMultTranspose_Normal in src/mat/impls/normal/normm.c
MatMultTranspose_ScaLAPACK in src/mat/impls/scalapack/matscalapack.c
MatMultTranspose_Scatter in src/mat/impls/scatter/mscatter.c
MatMultTranspose_MPISELL in src/mat/impls/sell/mpi/mpisell.c
MatMultTranspose_SeqSELL in src/mat/impls/sell/seq/sell.c
MatMultTranspose_Shell in src/mat/impls/shell/shell.c
MatMultTranspose_CF in src/mat/impls/shell/shellcnv.c
MatMultTranspose_SubMatrix in src/mat/impls/submat/submat.c
MatMultTranspose_Transpose in src/mat/impls/transpose/transm.c
---
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