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<div id="version" align=right><b>slepc-3.22.2 2024-12-02</b></div>
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<H1>MatNormEstimate</H1>
Estimate the 2-norm of a matrix.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
#include "slepcsys.h"
<A HREF="https://petsc.org/release/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../sys/MatNormEstimate.html#MatNormEstimate">MatNormEstimate</A>(<A HREF="https://petsc.org/release/manualpages/Mat/Mat.html#Mat">Mat</A> A,<A HREF="https://petsc.org/release/manualpages/Vec/Vec.html#Vec">Vec</A> vrn,<A HREF="https://petsc.org/release/manualpages/Vec/Vec.html#Vec">Vec</A> w,<A HREF="https://petsc.org/release/manualpages/Sys/PetscReal.html#PetscReal">PetscReal</A> *nrm)
</PRE>
Collective
<P>
<H3><FONT COLOR="#883300">Input Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>A </B></TD><TD> - the matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>vrn </B></TD><TD> - random vector with normally distributed entries (can be NULL)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>w </B></TD><TD> - workspace vector (can be NULL)
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Output Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>nrm </B></TD><TD> - the norm estimate
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
Does not need access to the matrix entries, just performs a matrix-vector product.
Based on work by I. Ipsen and coworkers https://ipsen.math.ncsu.edu/ps/slides_ima.pdf
<P>
The input vector vrn must have unit 2-norm.
If vrn is NULL, then it is created internally and filled with <A HREF="../sys/VecSetRandomNormal.html#VecSetRandomNormal">VecSetRandomNormal</A>().
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../sys/VecSetRandomNormal.html#VecSetRandomNormal">VecSetRandomNormal</A>()
<BR><P><B></B><H3><FONT COLOR="#883300">Level</FONT></H3>developer<BR>
<H3><FONT COLOR="#883300">Location</FONT></H3>
</B><A HREF="../../../src/sys/mat/matutil.c.html#MatNormEstimate">src/sys/mat/matutil.c</A>
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