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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
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<TITLE>SNESLineSearchSet</TITLE>
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<BODY BGCOLOR="FFFFFF">
<A NAME="SNESLineSearchSet"><H1>SNESLineSearchSet</H1></A>
Sets the line search routine to be used by the method <A HREF="../SNES/SNESLS.html#SNESLS">SNESLS</A>.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
PetscErrorCode PETSCSNES_DLLEXPORT SNESLineSearchSet(SNES snes,PetscErrorCode (*func)(SNES,void*,Vec,Vec,Vec,Vec,Vec,PetscReal,PetscReal,PetscReal*,PetscReal*,PetscTruth*),void *lsctx)
</PRE>
<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>snes </B></TD><TD>- nonlinear context obtained from <A HREF="../SNES/SNESCreate.html#SNESCreate">SNESCreate</A>()
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>lsctx </B></TD><TD>- optional user-defined context for use by line search
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>func </B></TD><TD>- pointer to int function
</TD></TR></TABLE>
<P>
Collective on <A HREF="../SNES/SNES.html#SNES">SNES</A>
<P>
<H3><FONT COLOR="#CC3333">Available Routines</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../SNES/SNESLineSearchCubic.html#SNESLineSearchCubic">SNESLineSearchCubic</A>() </B></TD><TD>- default line search
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../SNES/SNESLineSearchQuadratic.html#SNESLineSearchQuadratic">SNESLineSearchQuadratic</A>() </B></TD><TD>- quadratic line search
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../SNES/SNESLineSearchNo.html#SNESLineSearchNo">SNESLineSearchNo</A>() </B></TD><TD>- the full Newton step (actually not a line search)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../SNES/SNESLineSearchNoNorms.html#SNESLineSearchNoNorms">SNESLineSearchNoNorms</A>() </B></TD><TD>- the full Newton step (calculating no norms; faster in parallel)
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database Keys</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ls [cubic,quadratic,basic,basicnonorms] </B></TD><TD>- Selects line search
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ls_alpha <alpha> </B></TD><TD>- Sets alpha
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ls_maxstep <maxstep> </B></TD><TD>- Sets maximum step the line search will use (if the 2-norm(y) > maxstep then scale y to be y = (maxstep/2-norm(y)) *y)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ls_minlambda <minlambda> </B></TD><TD>- Sets the minimum lambda the line search will use minlambda / max_i ( y[i]/x[i] )
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Calling sequence of func</FONT></H3>
<PRE>
func (<A HREF="../SNES/SNES.html#SNES">SNES</A> snes,void *lsctx,<A HREF="../Vec/Vec.html#Vec">Vec</A> x,<A HREF="../Vec/Vec.html#Vec">Vec</A> f,<A HREF="../Vec/Vec.html#Vec">Vec</A> g,<A HREF="../Vec/Vec.html#Vec">Vec</A> y,<A HREF="../Vec/Vec.html#Vec">Vec</A> w,<A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> fnorm,<A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> xnorm,<A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> *ynorm,<A HREF="../Sys/PetscReal.html#PetscReal">PetscReal</A> *gnorm,<A HREF="../Sys/PetscTruth.html#PetscTruth">PetscTruth</A> *flag)
</PRE>
<P>
<H3><FONT COLOR="#CC3333">Input parameters for func</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>snes </B></TD><TD>- nonlinear context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>lsctx </B></TD><TD>- optional user-defined context for line search
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>x </B></TD><TD>- current iterate
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>f </B></TD><TD>- residual evaluated at x
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>y </B></TD><TD>- search direction
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>fnorm </B></TD><TD>- 2-norm of f
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output parameters for func</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>g </B></TD><TD>- residual evaluated at new iterate y
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>w </B></TD><TD>- new iterate
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>gnorm </B></TD><TD>- 2-norm of g
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ynorm </B></TD><TD>- 2-norm of search length
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>flag </B></TD><TD>- set to <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A> if the line search succeeds; <A HREF="../Sys/PETSC_FALSE.html#PETSC_FALSE">PETSC_FALSE</A> on failure.
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A>, nonlinear, set, line search, routine
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESLineSearchCubic.html#SNESLineSearchCubic">SNESLineSearchCubic</A>(), <A HREF="../SNES/SNESLineSearchQuadratic.html#SNESLineSearchQuadratic">SNESLineSearchQuadratic</A>(), <A HREF="../SNES/SNESLineSearchNo.html#SNESLineSearchNo">SNESLineSearchNo</A>(), <A HREF="../SNES/SNESLineSearchNoNorms.html#SNESLineSearchNoNorms">SNESLineSearchNoNorms</A>(),
<BR><A HREF="../SNES/SNESLineSearchSetPostCheck.html#SNESLineSearchSetPostCheck">SNESLineSearchSetPostCheck</A>(), <A HREF="../SNES/SNESLineSearchSetParams.html#SNESLineSearchSetParams">SNESLineSearchSetParams</A>(), <A HREF="../SNES/SNESLineSearchGetParams.html#SNESLineSearchGetParams">SNESLineSearchGetParams</A>(), <A HREF="../SNES/SNESLineSearchSetPreCheck.html#SNESLineSearchSetPreCheck">SNESLineSearchSetPreCheck</A>()
<P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/impls/ls/ls.c.html#SNESLineSearchSet">src/snes/impls/ls/ls.c</A>
<BR><A HREF="./index.html">Index of all SNES routines</A>
<BR><A HREF="../../index.html">Table of Contents for all manual pages</A>
<BR><A HREF="../singleindex.html">Index of all manual pages</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/snes/examples/tutorials/ex38.c.html">src/snes/examples/tutorials/ex38.c.html</A><BR>
<A HREF="../../../src/snes/examples/tutorials/ex1f.F.html">src/snes/examples/tutorials/ex1f.F.html</A><BR>
<A HREF="../../../src/snes/examples/tutorials/ex39f90.F.html">src/snes/examples/tutorials/ex39f90.F.html</A><BR>
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