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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
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<HEAD> <link rel="canonical" href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecNorm.html" />
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<TITLE>VecNorm</TITLE>
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<div id="version" align=right><b>petsc-3.14.5 2021-03-03</b></div>
<div id="bugreport" align=right><a href="mailto:petsc-maint@mcs.anl.gov?subject=Typo or Error in Documentation &body=Please describe the typo or error in the documentation: petsc-3.14.5 v3.14.5 docs/manualpages/Vec/VecNorm.html "><small>Report Typos and Errors</small></a></div>
<A NAME="VecNorm"><H1>VecNorm</H1></A>
Computes the vector norm.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscvec.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../Vec/VecNorm.html#VecNorm">VecNorm</A>(<A HREF="../Vec/Vec.html#Vec">Vec</A> x,<A HREF="../Vec/NormType.html#NormType">NormType</A> type,<A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> *val)
</PRE>
Collective on <A HREF="../Vec/Vec.html#Vec">Vec</A>
<P>
<H3><FONT COLOR="#CC3333">Input Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>x </B></TD><TD>- the vector
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>type </B></TD><TD>- one of <A HREF="../Vec/NORM_1.html#NORM_1">NORM_1</A>, <A HREF="../Vec/NORM_2.html#NORM_2">NORM_2</A>, <A HREF="../Vec/NORM_INFINITY.html#NORM_INFINITY">NORM_INFINITY</A>. Also available
<A HREF="../Vec/NORM_1_AND_2.html#NORM_1_AND_2">NORM_1_AND_2</A>, which computes both norms and stores them
in a two element array.
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>val </B></TD><TD>- the norm
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
<pre>
<A HREF="../Vec/NORM_1.html#NORM_1">NORM_1</A> denotes sum_i |x_i|
</pre>
<pre>
<A HREF="../Vec/NORM_2.html#NORM_2">NORM_2</A> denotes sqrt(sum_i |x_i|^2)
</pre>
<pre>
<A HREF="../Vec/NORM_INFINITY.html#NORM_INFINITY">NORM_INFINITY</A> denotes max_i |x_i|
</pre>
<P>
For complex numbers <A HREF="../Vec/NORM_1.html#NORM_1">NORM_1</A> 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.
<P>
<P>
<H3><FONT COLOR="#CC3333">Performance Issues</FONT></H3>
<pre>
per-processor memory bandwidth
</pre>
<pre>
interprocessor latency
</pre>
<pre>
work load inbalance that causes certain processes to arrive much earlier than others
</pre>
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Vec/VecDot.html#VecDot">VecDot</A>(), <A HREF="../Vec/VecTDot.html#VecTDot">VecTDot</A>(), <A HREF="../Vec/VecNorm.html#VecNorm">VecNorm</A>(), <A HREF="../Vec/VecDotBegin.html#VecDotBegin">VecDotBegin</A>(), <A HREF="../Vec/VecDotEnd.html#VecDotEnd">VecDotEnd</A>(), <A HREF="../Vec/VecNormAvailable.html#VecNormAvailable">VecNormAvailable</A>(),
<BR><A HREF="../Vec/VecNormBegin.html#VecNormBegin">VecNormBegin</A>(), <A HREF="../Vec/VecNormEnd.html#VecNormEnd">VecNormEnd</A>()
<P>
<P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>intermediate<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/vec/vec/interface/rvector.c.html#VecNorm">src/vec/vec/interface/rvector.c</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/vec/vec/tutorials/ex1.c.html">src/vec/vec/tutorials/ex1.c.html</A><BR>
<A HREF="../../../src/vec/vec/tutorials/ex11.c.html">src/vec/vec/tutorials/ex11.c.html</A><BR>
<A HREF="../../../src/vec/vec/tutorials/performance.c.html">src/vec/vec/tutorials/performance.c.html</A><BR>
<A HREF="../../../src/vec/vec/tutorials/ex1f.F90.html">src/vec/vec/tutorials/ex1f.F90.html</A><BR>
<A HREF="../../../src/vec/vec/tutorials/ex1f90.F90.html">src/vec/vec/tutorials/ex1f90.F90.html</A><BR>
<A HREF="../../../src/vec/vec/tutorials/ex11f.F.html">src/vec/vec/tutorials/ex11f.F.html</A><BR>
<A HREF="../../../src/vec/vec/tutorials/ex11f90.F90.html">src/vec/vec/tutorials/ex11f90.F90.html</A><BR>
<A HREF="../../../src/vec/vec/tutorials/ex20f90.F90.html">src/vec/vec/tutorials/ex20f90.F90.html</A><BR>
<A HREF="../../../src/mat/tutorials/ex2.c.html">src/mat/tutorials/ex2.c.html</A><BR>
<A HREF="../../../src/mat/tutorials/ex9.c.html">src/mat/tutorials/ex9.c.html</A><BR>
<A HREF="../../../src/dm/impls/stag/tutorials/ex1.c.html">src/dm/impls/stag/tutorials/ex1.c.html</A><BR>
<P><H3><FONT COLOR="CC3333">Implementations</FONT></H3><A HREF="../../../src/vec/vec/impls/mpi/kokkos/mpikok.kokkos.cxx.html#VecNorm_MPIKokkos">VecNorm_MPIKokkos in src/vec/vec/impls/mpi/kokkos/mpikok.kokkos.cxx</A><BR>
<A HREF="../../../src/vec/vec/impls/mpi/mpicuda/mpicuda.cu.html#VecNorm_MPICUDA">VecNorm_MPICUDA in src/vec/vec/impls/mpi/mpicuda/mpicuda.cu</A><BR>
<A HREF="../../../src/vec/vec/impls/mpi/mpiviennacl/mpiviennacl.cxx.html#VecNorm_MPIViennaCL">VecNorm_MPIViennaCL in src/vec/vec/impls/mpi/mpiviennacl/mpiviennacl.cxx</A><BR>
<A HREF="../../../src/vec/vec/impls/mpi/pvec2.c.html#VecNorm_MPI">VecNorm_MPI in src/vec/vec/impls/mpi/pvec2.c</A><BR>
<A HREF="../../../src/vec/vec/impls/nest/vecnest.c.html#VecNorm_Nest">VecNorm_Nest in src/vec/vec/impls/nest/vecnest.c</A><BR>
<A HREF="../../../src/vec/vec/impls/seq/bvec2.c.html#VecNorm_Seq">VecNorm_Seq in src/vec/vec/impls/seq/bvec2.c</A><BR>
<A HREF="../../../src/vec/vec/impls/seq/kokkos/veckok.kokkos.cxx.html#VecNorm_SeqKokkos">VecNorm_SeqKokkos in src/vec/vec/impls/seq/kokkos/veckok.kokkos.cxx</A><BR>
<A HREF="../../../src/vec/vec/impls/seq/seqcuda/veccuda2.cu.html#VecNorm_SeqCUDA">VecNorm_SeqCUDA in src/vec/vec/impls/seq/seqcuda/veccuda2.cu</A><BR>
<A HREF="../../../src/vec/vec/impls/seq/seqviennacl/vecviennacl.cxx.html#VecNorm_SeqViennaCL">VecNorm_SeqViennaCL in src/vec/vec/impls/seq/seqviennacl/vecviennacl.cxx</A><BR>
<BR><A HREF="./index.html">Index of all Vec routines</A>
<BR><A HREF="../../index.html">Table of Contents for all manual pages</A>
<BR><A HREF="../singleindex.html">Index of all manual pages</A>
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