:orphan:
# VecDot
Computes the vector dot product. 
## Synopsis
```
#include "petscvec.h"   
PetscErrorCode VecDot(Vec x, Vec y, PetscScalar *val)
```
Collective


## Input Parameters

- ***x -*** first vector
- ***y -*** second vector



## Output Parameter

- ***val -*** the dot product



## Performance Issues
```none
    per-processor memory bandwidth
    interprocessor latency
    work load imbalance that causes certain processes to arrive much earlier than others
```





## Notes for Users of Complex Numbers
For complex vectors, `VecDot()` computes
```none
val = (x,y) = y^H x,
```
where y^H denotes the conjugate transpose of y. Note that this corresponds to the usual "mathematicians" complex
inner product where the SECOND argument gets the complex conjugate. Since the `BLASdot()` complex conjugates the first
first argument we call the `BLASdot()` with the arguments reversed.

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


## See Also
 [](ch_vectors), `Vec`, `VecMDot()`, `VecTDot()`, `VecNorm()`, `VecDotBegin()`, `VecDotEnd()`, `VecDotRealPart()`

## Level
intermediate

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

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex49.c.html">src/ksp/ksp/tutorials/ex49.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex15.c.html">src/snes/tutorials/ex15.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex69.c.html">src/snes/tutorials/ex69.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/bound/tutorials/jbearing2.c.html">src/tao/bound/tutorials/jbearing2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/constrained/tutorials/maros.c.html">src/tao/constrained/tutorials/maros.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/constrained/tutorials/tomographyADMM.c.html">src/tao/constrained/tutorials/tomographyADMM.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/leastsquares/tutorials/tomography.c.html">src/tao/leastsquares/tutorials/tomography.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/pde_constrained/tutorials/elliptic.c.html">src/tao/pde_constrained/tutorials/elliptic.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/pde_constrained/tutorials/hyperbolic.c.html">src/tao/pde_constrained/tutorials/hyperbolic.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/pde_constrained/tutorials/parabolic.c.html">src/tao/pde_constrained/tutorials/parabolic.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/tutorials/ex3.c.html">src/tao/tutorials/ex3.c</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/mpi/kokkos/mpikok.kokkos.cxx.html#VecDot_MPIKokkos">VecDot_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#VecDot_MPIViennaCL">VecDot_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#VecDot_MPI">VecDot_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#VecDot_Nest">VecDot_Nest in src/vec/vec/impls/nest/vecnest.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/seq/bvec1.c.html#VecDot_Seq">VecDot_Seq in src/vec/vec/impls/seq/bvec1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/impls/seq/kokkos/veckok.kokkos.cxx.html#VecDot_SeqKokkos">VecDot_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#VecDot_SeqViennaCL">VecDot_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)