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<A NAME="VecStrideMax"><H1>VecStrideMax</H1></A>
Computes the maximum of subvector of a vector defined by a starting point and a stride and optionally its location.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscvec.h"
PetscErrorCode VecStrideMax(Vec v,PetscInt start,PetscInt *idex,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></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>index </B></TD><TD>- the location where the maximum occurred (pass <A HREF="../Sys/PETSC_NULL.html#PETSC_NULL">PETSC_NULL</A> if not required)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>nrm </B></TD><TD>- the max
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">C++ variants</FONT></H3><TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD> PetscReal VecStrideMax(Vec x,PetscInt i)<TD WIDTH=20></TD><TD>-></TD><TD WIDTH=20></TD><TD>VecStrideMax(x,i,PETSC_NULL,&r); return r;</TR></TD>
</TABLE>
<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 xa is the array representing the vector x, then this computes the max
of the array (xa[start],xa[start+stride],xa[start+2*stride], ....)
<P>
This is useful for computing, say the maximum of the pressure variable when
the pressure is stored (interlaced) with other variables, e.g., density, etc.
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/VecMax.html#VecMax">VecMax</A>(), <A HREF="../Vec/VecStrideNorm.html#VecStrideNorm">VecStrideNorm</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>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/vec/vec/utils/vinv.c.html#VecStrideMax">src/vec/vec/utils/vinv.c</A>
<BR><A HREF="./index.html">Index of all Vec routines</A>
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