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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="PCFieldSplitSetGKBDelay"><H1>PCFieldSplitSetGKBDelay</H1></A>
Sets the delay in the lower bound error estimate in 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/PCFieldSplitSetGKBDelay.html#PCFieldSplitSetGKBDelay">PCFieldSplitSetGKBDelay</A>(<A HREF="../PC/PC.html#PC">PC</A> pc,<A HREF="../Sys/PetscInt.html#PetscInt">PetscInt</A> delay)
</PRE>
Collective on <A HREF="../PC/PC.html#PC">PC</A>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
The algorithm uses a lower bound estimate of the error in energy norm as stopping criterion. The lower bound of the error ||u-u^k||_H
is expressed as a truncated sum. The error at iteration k can only be measured at iteration (k + delay), and thus the algorithm needs
at least (delay + 1) iterations to stop. For more details on the generalized Golub-Kahan bidiagonalization method and its lower bound stopping criterion, please refer to
<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>delay </B></TD><TD>- the delay window in the lower bound estimate
</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_delay </B></TD><TD>- default is 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/PCFieldSplitSetGKBNu.html#PCFieldSplitSetGKBNu">PCFieldSplitSetGKBNu</A>(), <A HREF="../PC/PCFieldSplitSetGKBTol.html#PCFieldSplitSetGKBTol">PCFieldSplitSetGKBTol</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#PCFieldSplitSetGKBDelay">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#PCFieldSplitSetGKBDelay_FieldSplit">PCFieldSplitSetGKBDelay_FieldSplit in src/ksp/pc/impls/fieldsplit/fieldsplit.c</A><BR>
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