petsc-3.7.1 2016-05-15
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VecNorm

Computes the vector norm.

Synopsis

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

Input Parameters

x - the vector Many br
type - one of NORM_1, NORM_2, NORM_INFINITY. Also available Many brNORM_1_AND_2, which computes both norms and stores them Many brin a two element array. Many br

Output Parameter

val -the norm Many br

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 Many brnorm of the absolutely values of the complex entries. In PETSc 3.6 and earlier releases it returned the 1 norm of Many brthe 1 norm of the complex entries (what is returned by the BLAS routine asum()). Both are valid norms but most Many brpeople expect the former. Many br

Many br

Performance Issues

   per-processor memory bandwidth
   interprocessor latency
   work load inbalance that causes certain processes to arrive much earlier than others

See Also

VecDot(), VecTDot(), VecNorm(), VecDotBegin(), VecDotEnd(), VecNormAvailable(),
VecNormBegin(), VecNormEnd() Many br

Level:intermediate
Location:
src/vec/vec/interface/rvector.c
Index of all Vec routines
Table of Contents for all manual pages
Index of all manual pages

Examples

src/vec/vec/examples/tutorials/ex1.c.html
src/vec/vec/examples/tutorials/ex11.c.html
src/vec/vec/examples/tutorials/ex1f.F.html
src/vec/vec/examples/tutorials/ex1f90.F.html
src/vec/vec/examples/tutorials/ex11f.F.html
src/vec/vec/examples/tutorials/ex20f90.F90.html
src/mat/examples/tutorials/ex2.c.html
src/mat/examples/tutorials/ex9.c.html
src/dm/examples/tutorials/ex10.c.html
src/ksp/ksp/examples/tutorials/ex1.c.html
src/ksp/ksp/examples/tutorials/ex2.c.html