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<TITLE>SNESLineSearchQuadratic</TITLE>
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<A NAME="SNESLineSearchQuadratic"><H1>SNESLineSearchQuadratic</H1></A>
Performs a quadratic line search.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
PetscErrorCode PETSCSNES_DLLEXPORT SNESLineSearchQuadratic(SNES snes,void *lsctx,Vec x,Vec f,Vec g,Vec y,Vec w,PetscReal fnorm,PetscReal xnorm,PetscReal *ynorm,PetscReal *gnorm,PetscTruth *flag)
</PRE>
Collective on <A HREF="../SNES/SNES.html#SNES">SNES</A> and <A HREF="../Vec/Vec.html#Vec">Vec</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>snes </B></TD><TD>- the <A HREF="../SNES/SNES.html#SNES">SNES</A> context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>lsctx </B></TD><TD>- optional context for line search (not used here)
</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>w </B></TD><TD>- work vector
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>fnorm </B></TD><TD>- 2-norm of f
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>xnorm </B></TD><TD>- norm of x if known, otherwise 0
</TD></TR></TABLE>
<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>g </B></TD><TD>- residual evaluated at new iterate w
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>w </B></TD><TD>- new iterate (x + lambda*y)
</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>- <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A> if line search succeeds; <A HREF="../Sys/PETSC_FALSE.html#PETSC_FALSE">PETSC_FALSE</A> on failure.
</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 quadratic </B></TD><TD>- Activates <A HREF="../SNES/SNESLineSearchQuadratic.html#SNESLineSearchQuadratic">SNESLineSearchQuadratic</A>()
</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 the maximum stepsize 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">Notes</FONT></H3>
Use <A HREF="../SNES/SNESLineSearchSet.html#SNESLineSearchSet">SNESLineSearchSet</A>() to set this routine within the <A HREF="../SNES/SNESLS.html#SNESLS">SNESLS</A> method.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A>, nonlinear, quadratic, line search
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESLineSearchCubic.html#SNESLineSearchCubic">SNESLineSearchCubic</A>(), <A HREF="../SNES/SNESLineSearchNo.html#SNESLineSearchNo">SNESLineSearchNo</A>(), <A HREF="../SNES/SNESLineSearchSet.html#SNESLineSearchSet">SNESLineSearchSet</A>(), <A HREF="../SNES/SNESLineSearchNoNorms.html#SNESLineSearchNoNorms">SNESLineSearchNoNorms</A>()
<BR><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#SNESLineSearchQuadratic">src/snes/impls/ls/ls.c</A>
<BR><A HREF="./index.html">Index of all SNES routines</A>
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