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<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
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<A NAME="PCHYPRE"><H1>PCHYPRE</H1></A>
Allows you to use the matrix element based preconditioners in the LLNL package hypre
<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>-pc_hypre_type </B></TD><TD>- One of pilut, parasails, boomeramg, ams, ads
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Too many others to list, run with </B></TD><TD>- pc_type hypre -pc_hypre_type XXX -help to see options for the XXX
preconditioner
</TD></TR></TABLE>
<P>
<P>
Notes: Apart from pc_hypre_type (for which there is <A HREF="../PC/PCHYPRESetType.html#PCHYPRESetType">PCHYPRESetType</A>()),
the many hypre options can ONLY be set via the options database (e.g. the command line
or with <A HREF="../Sys/PetscOptionsSetValue.html#PetscOptionsSetValue">PetscOptionsSetValue</A>(), there are no functions to set them)
<P>
The options -pc_hypre_boomeramg_max_iter and -pc_hypre_boomeramg_rtol refer to the number of iterations
(V-cycles) and tolerance that boomeramg does EACH time it is called. So for example, if
-pc_hypre_boomeramg_max_iter is set to 2 then 2-V-cycles are being used to define the preconditioner
(-pc_hypre_boomeramg_rtol should be set to 0.0 - the default - to strictly use a fixed number of
iterations per hypre call). -ksp_max_it and -ksp_rtol STILL determine the total number of iterations
and tolerance for the Krylov solver. For example, if -pc_hypre_boomeramg_max_iter is 2 and -ksp_max_it is 10
then AT MOST twenty V-cycles of boomeramg will be called.
<P>
Note that the option -pc_hypre_boomeramg_relax_type_all defaults to symmetric relaxation
(symmetric-SOR/Jacobi), which is required for Krylov solvers like CG that expect symmetry.
Otherwise, you may want to use -pc_hypre_boomeramg_relax_type_all SOR/Jacobi.
If you wish to use BoomerAMG WITHOUT a Krylov method use -ksp_type richardson NOT -ksp_type preonly
and use -ksp_max_it to control the number of V-cycles.
(see the PETSc FAQ.html at the PETSc website under the Documentation tab).
<P>
2007-02-03 Using HYPRE-1.11.1b, the routine HYPRE_BoomerAMGSolveT and the option
-pc_hypre_parasails_reuse were failing with SIGSEGV. Dalcin L.
<P>
<A HREF="../Mat/MatSetNearNullSpace.html#MatSetNearNullSpace">MatSetNearNullSpace</A>() - if you provide a near null space to your matrix it is ignored by hypre UNLESS you also use
<H3><FONT COLOR="#CC3333">the two options</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_hypre_boomeramg_nodal_coarsen <n> </B></TD><TD>- where n is from 1 to 6 (see HYPRE_BOOMERAMGSetNodal())
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_hypre_boomeramg_vec_interp_variant <v> where v is from 1 to 3 (see HYPRE_BoomerAMGSetInterpVecVariant())</B></TD><TD>-
Depending on the linear system you may see the same or different convergence depending on the values you use.
</TD></TR></TABLE>
<P>
See <A HREF="../PC/PCPFMG.html#PCPFMG">PCPFMG</A> for access to the hypre Struct PFMG solver
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCCreate.html#PCCreate">PCCreate</A>(), <A HREF="../PC/PCSetType.html#PCSetType">PCSetType</A>(), <A HREF="../PC/PCType.html#PCType">PCType</A> (for list of available types), <A HREF="../PC/PC.html#PC">PC</A>,
<BR><A HREF="../PC/PCHYPRESetType.html#PCHYPRESetType">PCHYPRESetType</A>(), <A HREF="../PC/PCPFMG.html#PCPFMG">PCPFMG</A>
<P>
<P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/pc/impls/hypre/hypre.c.html#PCHYPRE">src/ksp/pc/impls/hypre/hypre.c</A>
<BR><A HREF="./index.html">Index of all PC routines</A>
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