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<div id="version" align=right><b>petsc-3.10.3 2018-12-18</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-3.10.3 v3.10.3 docs/manualpages/KSP/KSPLSQRGetNorms.html "><small>Report Typos and Errors</small></a></div>
<A NAME="KSPLSQRGetNorms"><H1>KSPLSQRGetNorms</H1></A>
Get norm estimates that LSQR computes internally during <A HREF="../KSP/KSPSolve.html#KSPSolve">KSPSolve</A>().
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscksp.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../KSP/KSPLSQRGetNorms.html#KSPLSQRGetNorms">KSPLSQRGetNorms</A>(<A HREF="../KSP/KSP.html#KSP">KSP</A> ksp,<A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> *arnorm, <A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> *anorm)
</PRE>
Not Collective
<P>
<H3><FONT COLOR="#CC3333">Input Parameters</FONT></H3>
<DT><B>ksp </B> -iterative context
<br>
<P>
<H3><FONT COLOR="#CC3333">Output Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>arnorm </B></TD><TD>- good estimate of norm((A*inv(Pmat))'*r), where r = A*x - b, used in specific stopping criterion
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>anorm </B></TD><TD>- poor estimate of norm(A*inv(Pmat),'fro') used in specific stopping criterion
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
Output parameters are meaningful only after <A HREF="../KSP/KSPSolve.html#KSPSolve">KSPSolve</A>().
These are the same quantities as normar and norma in MATLAB's lsqr(), whose output lsvec is a vector of normar / norma for all iterations.
If -ksp_lsqr_exact_mat_norm is set or <A HREF="../KSP/KSPLSQRSetExactMatNorm.html#KSPLSQRSetExactMatNorm">KSPLSQRSetExactMatNorm</A>(ksp, <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A>) called, then anorm is exact Frobenius norm.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../KSP/KSP.html#KSP">KSP</A>, <A HREF="../KSP/KSPLSQR.html#KSPLSQR">KSPLSQR</A>
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../KSP/KSPSolve.html#KSPSolve">KSPSolve</A>(), <A HREF="../KSP/KSPLSQR.html#KSPLSQR">KSPLSQR</A>, <A HREF="../KSP/KSPLSQRSetExactMatNorm.html#KSPLSQRSetExactMatNorm">KSPLSQRSetExactMatNorm</A>()
<BR><P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>intermediate<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/ksp/ksp/impls/lsqr/lsqr.c.html#KSPLSQRGetNorms">src/ksp/ksp/impls/lsqr/lsqr.c</A>
<BR><A HREF="./index.html">Index of all KSP routines</A>
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