petsc-3.7.5 2017-01-01

VecDot

Computes the vector dot product.

Synopsis

#include "petscvec.h"   
PetscErrorCode  VecDot(Vec x,Vec y,PetscScalar *val)

Collective on Vec

Input Parameters

x, y -the vectors

Output Parameter

val -the dot product

Performance Issues

   per-processor memory bandwidth

   interprocessor latency

   work load inbalance that causes certain processes to arrive much earlier than others

Notes for Users of Complex Numbers

For complex vectors, VecDot() computes

    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

    val = (x,y) = y^T x,

where y^T denotes the transpose of y.

Examples