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# VecMDot
Computes multiple vector dot products. 
## Synopsis
```
#include "petscvec.h"   
PetscErrorCode VecMDot(Vec x, PetscInt nv, const Vec y[], PetscScalar val[])
```
Collective


## Input Parameters

- ***x -*** one vector
- ***nv -*** number of vectors
- ***y -*** array of vectors.



## Output Parameter

- ***val -*** array of the dot products (does not allocate the array)





## Notes for Users of Complex Numbers
For complex vectors, `VecMDot()` computes
```none
val = (x,y) = y^H x,
```
where y^H denotes the conjugate transpose of y.

Use `VecMTDot()` for the indefinite form
```none
val = (x,y) = y^T x,
```
where y^T denotes the transpose of y.


## See Also
 [](ch_vectors), `Vec`, `VecMTDot()`, `VecDot()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/interface/rvector.c.html#VecMDot">src/vec/vec/interface/rvector.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/tutorials/ex1.c.html">src/vec/vec/tutorials/ex1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/tutorials/ex1f.F90.html">src/vec/vec/tutorials/ex1f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/tutorials/ex1f90.F90.html">src/vec/vec/tutorials/ex1f90.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/tutorials/ex20f90.F90.html">src/vec/vec/tutorials/ex20f90.F90</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/mpi/kokkos/mpikok.kokkos.cxx.html#VecMDot_MPIKokkos">VecMDot_MPIKokkos in src/vec/vec/impls/mpi/kokkos/mpikok.kokkos.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/mpi/mpiviennacl/mpiviennacl.cxx.html#VecMDot_MPIViennaCL">VecMDot_MPIViennaCL in src/vec/vec/impls/mpi/mpiviennacl/mpiviennacl.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/mpi/pvec2.c.html#VecMDot_MPI">VecMDot_MPI in src/vec/vec/impls/mpi/pvec2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/nest/vecnest.c.html#VecMDot_Nest">VecMDot_Nest in src/vec/vec/impls/nest/vecnest.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/seq/dvec2.c.html#VecMDot_Seq">VecMDot_Seq in src/vec/vec/impls/seq/dvec2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/seq/dvec2.c.html#VecMDot_Seq">VecMDot_Seq in src/vec/vec/impls/seq/dvec2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/seq/kokkos/veckok.kokkos.cxx.html#VecMDot_SeqKokkos">VecMDot_SeqKokkos in src/vec/vec/impls/seq/kokkos/veckok.kokkos.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/seq/seqviennacl/vecviennacl.cxx.html#VecMDot_SeqViennaCL">VecMDot_SeqViennaCL in src/vec/vec/impls/seq/seqviennacl/vecviennacl.cxx</A><BR>


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


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