petsc-3.9.4 2018-09-11

VecNorm

Computes the vector norm.

Synopsis

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

Collective on Vec

Input Parameters

	x	- the vector
	type	- one of NORM_1, NORM_2, NORM_INFINITY. Also available NORM_1_AND_2, which computes both norms and stores them in a two element array.

Output Parameter

val -the norm

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 absolutely 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

Level

intermediate

VecNorm

Synopsis

Input Parameters

Output Parameter

Notes

Performance Issues

See Also

Level

Location

Examples

Implementations