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<div id="version" align=right><b>petsc-3.10.3 2018-12-18</b></div>
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<A NAME="PCDiagonalScaleLeft"><H1>PCDiagonalScaleLeft</H1></A>
Scales a vector by the left scaling as needed by certain time-stepping codes.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscksp.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../PC/PCDiagonalScaleLeft.html#PCDiagonalScaleLeft">PCDiagonalScaleLeft</A>(<A HREF="../PC/PC.html#PC">PC</A> pc,<A HREF="../Vec/Vec.html#Vec">Vec</A> in,<A HREF="../Vec/Vec.html#Vec">Vec</A> out)
</PRE>
Logically Collective on <A HREF="../PC/PC.html#PC">PC</A>
<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>in </B></TD><TD>- input vector
+ out - scaled vector (maybe the same as in)
</TD></TR>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
The system solved via the Krylov method is
<pre>
D M A D^{-1} y = D M b for left preconditioning or
</pre>
<pre>
D A M D^{-1} z = D b for right preconditioning
</pre>
<P>
<A HREF="../PC/PCDiagonalScaleLeft.html#PCDiagonalScaleLeft">PCDiagonalScaleLeft</A>() scales a vector by D. <A HREF="../PC/PCDiagonalScaleRight.html#PCDiagonalScaleRight">PCDiagonalScaleRight</A>() scales a vector by D^{-1}.
<P>
If diagonal scaling is turned off and in is not out then in is copied to out
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../PC/PC.html#PC">PC</A>
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCCreate.html#PCCreate">PCCreate</A>(), <A HREF="../PC/PCSetUp.html#PCSetUp">PCSetUp</A>(), PCDiagonalScaleSet(), <A HREF="../PC/PCDiagonalScaleRight.html#PCDiagonalScaleRight">PCDiagonalScaleRight</A>(), PCDiagonalScale()
<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/interface/precon.c.html#PCDiagonalScaleLeft">src/ksp/pc/interface/precon.c</A>
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