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<div id="version" align=right><b>petsc-3.14.5 2021-03-03</b></div>
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<A NAME="PCFieldSplitSetGKBTol"><H1>PCFieldSplitSetGKBTol</H1></A>
Sets the solver tolerance for the generalized Golub-Kahan bidiagonalization preconditioner.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscpc.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../PC/PCFieldSplitSetGKBTol.html#PCFieldSplitSetGKBTol">PCFieldSplitSetGKBTol</A>(<A HREF="../PC/PC.html#PC">PC</A> pc,<A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> tolerance)
</PRE>
Collective on <A HREF="../PC/PC.html#PC">PC</A>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
The generalized GKB algorithm uses a lower bound estimate of the error in energy norm as stopping criterion.
It stops once the lower bound estimate undershoots the required solver tolerance. Although the actual error might be bigger than
this estimate, the stopping criterion is satisfactory in practical cases [A13].
<P>
[Ar13] Generalized Golub-Kahan bidiagonalization and stopping criteria, SIAM J. Matrix Anal. Appl., Vol. 34, No. 2, pp. 571-592, 2013.
<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>pc </B></TD><TD>- the preconditioner context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>tolerance </B></TD><TD>- the solver tolerance
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_fieldsplit_gkb_tol </B></TD><TD>- default is 1e-5
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCFIELDSPLIT.html#PCFIELDSPLIT">PCFIELDSPLIT</A>, <A HREF="../PC/PCFieldSplitSetGKBDelay.html#PCFieldSplitSetGKBDelay">PCFieldSplitSetGKBDelay</A>(), <A HREF="../PC/PCFieldSplitSetGKBNu.html#PCFieldSplitSetGKBNu">PCFieldSplitSetGKBNu</A>(), <A HREF="../PC/PCFieldSplitSetGKBMaxit.html#PCFieldSplitSetGKBMaxit">PCFieldSplitSetGKBMaxit</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/pc/impls/fieldsplit/fieldsplit.c.html#PCFieldSplitSetGKBTol">src/ksp/pc/impls/fieldsplit/fieldsplit.c</A>
<P><H3><FONT COLOR="CC3333">Implementations</FONT></H3><A HREF="../../../src/ksp/pc/impls/fieldsplit/fieldsplit.c.html#PCFieldSplitSetGKBTol_FieldSplit">PCFieldSplitSetGKBTol_FieldSplit in src/ksp/pc/impls/fieldsplit/fieldsplit.c</A><BR>
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