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<TITLE>VecStrideNorm</TITLE>
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<A NAME="VecStrideNorm"><H1>VecStrideNorm</H1></A>
Computes the norm of subvector of a vector defined by a starting point and a stride.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscvec.h"
int VecStrideNorm(Vec v,int start,NormType ntype,PetscReal *nrm)
</PRE>
Collective on <A HREF="../Vec/Vec.html#Vec">Vec</A>
<P>
<H3><FONT COLOR="#CC3333">Input Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>v </B></TD><TD>- the vector
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>start </B></TD><TD>- starting point of the subvector (defined by a stride)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ntype </B></TD><TD>- type of norm, one of NORM_1, NORM_2, NORM_INFINITY
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameter</FONT></H3>
<DT><B>norm </B> -the norm
<br>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
One must call <A HREF="../Vec/VecSetBlockSize.html#VecSetBlockSize">VecSetBlockSize</A>() before this routine to set the stride
information, or use a vector created from a multicomponent <A HREF="../DA/DA.html#DA">DA</A>.
<P>
If x is the array representing the vector x then this computes the norm
of the array (x[start],x[start+stride],x[start+2*stride], ....)
<P>
This is useful for computing, say the norm of the pressure variable when
the pressure is stored (interlaced) with other variables, say density etc.
<P>
This will only work if the desire subvector is a stride subvector
<P>
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Vec/VecNorm.html#VecNorm">VecNorm</A>(), <A HREF="../Vec/VecStrideGather.html#VecStrideGather">VecStrideGather</A>(), <A HREF="../Vec/VecStrideScatter.html#VecStrideScatter">VecStrideScatter</A>(), <A HREF="../Vec/VecStrideMin.html#VecStrideMin">VecStrideMin</A>(), <A HREF="../Vec/VecStrideMax.html#VecStrideMax">VecStrideMax</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/vec/utils/vinv.c.html#VecStrideNorm">src/vec/utils/vinv.c</A>
<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>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/vec/examples/tutorials/ex11.c.html">src/vec/examples/tutorials/ex11.c.html</A><BR>
<A HREF="../../../src/vec/examples/tutorials/ex11f.F.html">src/vec/examples/tutorials/ex11f.F.html</A><BR>
<A HREF="../../../src/snes/examples/tutorials/ex22.c.html">src/snes/examples/tutorials/ex22.c.html</A><BR>
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