More documentation.

git-svn-id: https://svn.cct.lsu.edu/repos/numrel/LSUThorns/SummationByParts/trunk@25 f69c4107-0314-4c4f-9ad4-17e986b73f4a

1 files changed, 48 insertions, 4 deletions

diff --git a/doc/documentation.tex b/doc/documentation.tex
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--- a/doc/documentation.tex
+++ b/doc/documentation.tex
@@ -193,12 +193,53 @@ restricted full norm 6-5 operator has been implemented. This was calculated
 using a Mathematica script kindly provided by Jos\'{e} M.
 Mart\'{\i}n-Garc\'{\i}a.
 
+For the restricted full norm 6-5 SBP operators a compatible dissipation
+operator has been implemented as well based on \cite{msn04}.
 \section{Using This Thorn}
-
+The basic functionality of calculating finite difference approximations are
+performed by a set of aliased functions. In this way things are kept flexible
+in the sense that different thorns each can provide their own way of
+calculating derivatives but if they use the same calling interface the
+user can switch between different derivative schemes by simply activating
+the appropriate finite differencing thorn.
+
+There are currently two different calling interfaces corresponding to different
+levels of flexibility. In the first case the fact that derivatives are
+approximated by finite differencing is completely hidden for the user. Using
+this interface the same physics thorn could in principle be used with a
+finite difference driver, a finite elements driver or a spectral driver. There
+is however a price to pay for this flexibility due to the fact that the
+operations are performed on whole grid functions at a time so that storage
+for the derivatives has to be provided. This can significantly increase the
+amount of memery required for the evolution. The alternative interface
+returns instead the finite difference coefficients and allows the user to
+calculate derivatives on a pointwise basis. This can significantly save
+memory but limits the physics thorn to use finite differences.
 \subsection{Obtaining This Thorn}
-
+The thorn is currently still in development and so is not generally available.
+Access can be requested by contacting the thorn maintainer.
 \subsection{Basic Usage}
-
+In order to use the derivative routines the appropriate declarations have 
+to be added to your thorns interface.ccl file. To use the interface that
+works on whole grid functions you have to add:
+\begin{verbatim}
+SUBROUTINE Diff_gv ( CCTK_POINTER_TO_CONST IN cctkGH, \
+                     CCTK_INT IN dir, \
+                     CCTK_REAL IN ARRAY var, \
+                     CCTK_REAL OUT ARRAY dvar )
+USES FUNCTION Diff_gv
+\end{verbatim}
+To use the interface that returns the finite difference coefficients you have 
+to add:
+\begin{verbatim}
+SUBROUTINE Diff_coeff ( CCTK_POINTER_TO_CONST IN cctkGH, \
+                        CCTK_INT IN dir, \
+                        CCTK_INT IN nsize, \
+                        CCTK_INT OUT ARRAY imin, \
+                        CCTK_INT OUT ARRAY imax, \
+                        CCTK_REAL OUT ARRAY q, \
+                        CCTK_INT IN table_handle )
+\end{verbatim}
 \subsection{Special Behaviour}
 
 \subsection{Interaction With Other Thorns}
@@ -217,8 +258,11 @@ Mart\'{\i}n-Garc\'{\i}a.
 
 
 \begin{thebibliography}{9}
-\bibitem{strand93} Bo Strand, 1994, Journal of Computational Physics, 110, 47-67
+\bibitem{strand93} Bo Strand, 1994, Journal of Computational Physics, 110,
+47--67.
 \bibitem{lrt05} Luis Lehner, Oscar Reula and Manuel Tiglio, in preparation.
+\bibitem{msn04} Ken Mattsson, Magnus Sv\"{a}rd and Jan Nordstr\"{o}m, 2004,
+Journal of Scientific Computing, 21, 57--79.
 
 \end{thebibliography}