As per my proposal in

   http://www.cactuscode.org/pipermail/developers/2005-March/000815.html
add a new parameter  copy_ID_after_MoL_PostStep  to control precisely
*when* in CCTK_POSTINITIAL  MoL_FillAllLevels  is scheduled
if  initial_data_is_crap  is set.

The default (MoL_FillAllLevels is scheduled *before* MoL_PostStep)
matches the previous behavior, so there's no change required to par
files unless you want the new behavior (MoL_FillAllLevels is scheduled
*after* MoL_PostStep).


git-svn-id: http://svn.cactuscode.org/arrangements/CactusNumerical/MoL/trunk@87 578cdeb0-5ea1-4b81-8215-5a3b8777ee0b

1 files changed, 25 insertions, 2 deletions

diff --git a/doc/documentation.tex b/doc/documentation.tex
index b8ca497..928c337 100644
--- a/doc/documentation.tex
+++ b/doc/documentation.tex
@@ -248,8 +248,31 @@ are using mesh refinement, and in particular {\tt Carpet}. With mesh
 refinement it may be necessary to disable prolongation in intermediate
 steps of MoL. This occurs when evolving systems containing second
 spatial derivatives. This is done by default in MoL. If your system is
-purely first order in space and time you may wish to set this to {\tt
-  "no"}.
+purely first order in space and time you may wish to set this to {\tt "no"}.
+
+Ideally, initial data thorns should always set initial data at all time
+levels.  However, sometimes initial data thorns fail to do this.  In
+this case you can do one of three things:
+\begin{itemize}
+\item	Fix the initial data thorn.  This is the best solution.
+\item	If you're using Carpet, it has some facilities to take
+	forward/backward time steps to initialize multiple time
+	levels.  See the Carpet parameters
+	\verb|init_each_timelevel| and
+	\verb|init_3_timelevels| for details.
+\item	Finally, if you set (the MoL parameter) \verb|initial_data_is_crap|,
+	MoL will copy the current time level to all the past time
+	levels.  \textbf{Note that this copies the \underline{same}
+	data to each past time level; this will be wrong if your
+	spacetime is time-dependent!}
+
+	If enabled, the copy happens in the \verb|CCTK_POSTINITIAL|
+	schedule bin.  By default this happens \emph{before}
+	the \verb|MoL_PostStep| schedule group; the parameter
+	\verb|copy_ID_after_MoL_PostStep| can be used to change
+	this to \emph{after} \verb|MoL_PostStep|.
+\end{itemize}
+
 
 \subsection{Thorn writers}
 \label{CactusBase_MoL_sec:writeruse}