VecNorm

Synopsis

#include "petscvec.h"   
PetscErrorCode  VecNorm(Vec x,NormType type,PetscReal *val)

Input Parameters

Output Parameter

Notes

    NORM_1 denotes sum_i |x_i|

    NORM_2 denotes sqrt(sum_i |x_i|^2)

    NORM_INFINITY denotes max_i |x_i|

For complex numbers NORM_1 will return the traditional 1 norm of the 2 norm of the complex numbers; that is the 1 norm of the absolute values of the complex entries. In PETSc 3.6 and earlier releases it returned the 1 norm of the 1 norm of the complex entries (what is returned by the BLAS routine asum()). Both are valid norms but most people expect the former.

Performance Issues

   per-processor memory bandwidth

   interprocessor latency

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

See Also

Level

Location

Examples

Implementations