CoordBase thorn, which implements the Coordinate spec

git-svn-id: http://svn.cactuscode.org/arrangements/CactusBase/CoordBase/trunk@2 0337457d-221f-4ee6-a5f0-14255d5370d8

10 files changed, 1450 insertions, 0 deletions

diff --git a/README b/README
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+Cactus Code Thorn CoordBase
+Authors    : Cactus Maintainers <cactusmaint@cactuscode.org>
+CVS info   : $Header$
+--------------------------------------------------------------------------
+
+Purpose of the thorn:
+
+Provides generic handling of coordinates for grid arrays.
diff --git a/doc/documentation.tex b/doc/documentation.tex
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+++ b/doc/documentation.tex
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+% *======================================================================*
+%  Cactus Thorn template for ThornGuide documentation
+%  Author: Ian Kelley
+%  Date: Sun Jun 02, 2002
+%  $Header$                                                             
+%  Thorn documentation in the latex file doc/documentation.tex 
+%  will be included in ThornGuides built with the Cactus make system.
+%  The scripts employed by the make system automatically include 
+%  pages about variables, parameters and scheduling parsed from the 
+%  relevent thorn CCL files.
+%  
+%  This template contains guidelines which help to assure that your     
+%  documentation will be correctly added to ThornGuides. More 
+%  information is available in the Cactus UsersGuide.
+%                                                    
+%  Guidelines:
+%   - Do not change anything before the line
+%       % BEGIN CACTUS THORNGUIDE",
+%     except for filling in the title, author, date etc. fields.
+%        - Each of these fields should only be on ONE line.
+%        - Author names should be sparated with a \\ or a comma
+%   - You can define your own macros are OK, but they must appear after
+%     the BEGIN CACTUS THORNGUIDE line, and must not redefine standard 
+%     latex commands.
+%   - To avoid name clashes with other thorns, 'labels', 'citations', 
+%     'references', and 'image' names should conform to the following 
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+%       ARRANGEMENT_THORN_LABEL
+%     For example, an image wave.eps in the arrangement CactusWave and 
+%     thorn WaveToyC should be renamed to CactusWave_WaveToyC_wave.eps
+%   - Graphics should only be included using the graphix package. 
+%     More specifically, with the "includegraphics" command. Do
+%     not specify any graphic file extensions in your .tex file. This 
+%     will allow us (later) to create a PDF version of the ThornGuide
+%     via pdflatex. |
+%   - References should be included with the latex "bibitem" command. 
+%   - use \begin{abstract}...\end{abstract} instead of \abstract{...}
+%   - For the benefit of our Perl scripts, and for future extensions, 
+%     please use simple latex.     
+%
+% *======================================================================* 
+% 
+% Example of including a graphic image:
+%    \begin{figure}[ht]
+% 	\begin{center}
+%    	   \includegraphics[width=6cm]{MyArrangement_MyThorn_MyFigure}
+% 	\end{center}
+% 	\caption{Illustration of this and that}
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+%
+% Example of including a reference
+%   \bibitem{MyArrangement_MyThorn_Author99}
+%   {J. Author, {\em The Title of the Book, Journal, or periodical}, 1 (1999), 
+%   1--16. {\tt http://www.nowhere.com/}}
+%
+% *======================================================================* 
+
+% If you are using CVS use this line to give version information
+% $Header$
+
+\documentclass{article}
+
+% Use the Cactus ThornGuide style file
+% (Automatically used from Cactus distribution, if you have a 
+%  thorn without the Cactus Flesh download this from the Cactus
+%  homepage at www.cactuscode.org)
+\usepackage{../../../../doc/latex/cactus}
+
+\begin{document}
+
+% The author of the documentation
+\author{Cactus Maintainers $<$\code{cactusmaint@cactuscode.org}$>$}
+
+% The title of the document (not necessarily the name of the Thorn)
+\title{Coordinate Base Thorn}
+
+% the date your document was last changed:
+\date{$ $Date$ $}
+
+\maketitle
+
+% Do not delete next line
+% START CACTUS THORNGUIDE
+
+% Add all definitions used in this documentation here:
+\def\WHAGH{CCTK\_WHAGH}
+\def\beforetable{\\[1mm]}
+
+\hyphenation{Coord}
+
+% Add an abstract for this thorn's documentation
+\begin{abstract}
+CoordBase provides a mechanism for registering coordinate systems, and
+maintaining a database of coordinate systems and their coordinates,
+using key-value tables.
+\end{abstract}
+
+
+\section{Introduction}
+
+Many applications which use Cactus will want to make use of coordinate
+systems.  The CoordBase thorn provides a method of registering
+coordinate systems and their properties.  Thorns which implement
+coordinate systems will register the systems they provide with
+CoordBase.  Since coordinate systems are composed of a collection of
+coordinates, the coordinates which comprise the systems are registered
+with CoordBase as well.  The data describing coordinate systems are
+held on Cactus key-value tables.  A schema for the format of these
+tables is provided in section
+\ref{CactusBase_CoordBase_coordinate_schema}.  Developers are free to
+compose and use their own schema, but are encouraged to use the one
+detailed here, as this will be the standard for all of the core Cactus
+thorns.
+
+CoordBase specifies an extensible set of coordinate properties.  The
+use of key-value tables to hold the these properties makes CoordBase
+flexible and configurable.  The coordinate values themselves can be
+specified in a number of ways, depending on the nature of the
+coordinate system.  This way symmetries of the coordinates on the
+computational grid can be exploited to minimize memory consumption.
+Via a function call, one can easily acertain what coordinate system is
+associated with any given grid variable, which is convenient for e.g.\
+I/O.  A method of registering default coordinates for all grid
+variables of a certain dimension makes it simple to specify which
+coordinate systems should be associated with which grid variables.
+
+The coordinate infrastructure provided by CoordBase will work
+seamlessly with AMR and multi-model codes.
+
+%extensible database of coordinate systems, coordinates, and their
+%properties
+
+Thorns which provide coordinates will inherit from CoordBase, and
+register both the coordinate systems they provide, and the default
+coordinate systems for the appropriate dimension of grid variables.
+In addition, one can associate a coordinate with any Cactus grid
+variable, within a thorn's interface.ccl.
+Coordinate systems specified in the interface.ccl override defaults
+for the dimension.
+
+The coordinate functions in the Cactus flesh are deprecated with the
+introduction of this thorn.  Please use the functions provided here in
+preference to those in the flesh.
+
+
+\section{Coordinate system symmetries}
+
+Since computations performed with Cactus are done on a discrete
+lattice, only a discrete set of coordinate values are used for any
+coordinate system.  The symmetries of how the coordinate values vary
+on the grid points make coordinates fall into three types:
+\emph{uniform}, \emph{nonuniform}, and \emph{warped}.  (At least these
+are the three cases that the CoordBase schema considers.)  A uniform
+coordinate varies from each of its neighbors by a constant.  i.e.\ its
+value can be determined from the index of the grid point from simply
+an origin and constant `delta'.  A nonuniform coordinate has a
+spatially varying `delta'.  For both uniform and nonuniform
+coordinates, the coordinate values do not vary along the other
+directions of the grid.  (e.g.\ the $x$ coordinate will be the same
+regardless of the `j' index of the grid point.)  Thus one could
+completely determine the coordinate values of a 3D system of
+nonuniform coordinates by providing three 1D arrays.  This later
+assumption is relaxed for a warped coordinate; a warped coordinate
+will vary across the entire grid.  Recall that `coordinate lines'
+(lines of constant coordinate value) cannot cross (because one n-tuple
+of coordinate values would specify muliple points in space), so this
+places a `bound' of sorts on the possible `warping' of the
+coordinates.
+
+The type of a coordinate system will be the same as that of its
+coordinates.  If there are different types of coordinates within the
+same system, then the coordinate system is \emph{mixed}.  Note that a
+warped coordinate system is the most general possible, so any
+coordinate system could be regarded as warped if one wishes.
+
+\subsection{Specifying coordinate values}
+
+As mentioned above, for a uniform coordinate system, it is sufficient
+to specify the origin and spacing for a uniform coordinate.  One may
+also specify a grid variable to hold the coordinate values, if
+desired.  See section \ref{CactusBase_CoordBase_coordinate_schema}.  A
+nonuniform coordinate can be specified with a 1D grid variable, if
+desired, or an nD variable.  A warped coordinate system will always
+need a nD grid variable.  FMR and AMR will need an nD grid
+variable to specify the coordinate values.  A mixed coordinate system
+can use some combination of the above, or simply an nD grid variable.
+
+
+\section{Coordinate Thorns}
+
+Generally coordinate thorns will allow the declaration of default
+coordinate systems for a dimension to be controled by parameters.
+
+If a thorn attempts to register a default for a dimension which
+already has a default registered, a level 1 warning will result, and
+the default will be overwritten with the new default.  Since the order
+of execution of the registration calls will in general not be
+specified, one must be careful when activating more than one coordinate thorn.
+
+Coordinate systems and defaults can be changed at any time throughout
+a run, as can coordinate properties.
+In general these are set at \WHAGH\ and CCTK\_BASEGRID, respectively.
+
+The coordinate thorns are responsible for filling out the portions of
+the coordinate and coordinate system tables that are not written by
+the registration routines.  See sections
+\ref{CactusBase_CoordBase_system_tables} and
+\ref{CactusBase_CoordBase_coord_tables}.
+
+\section{Application thorns}
+
+Application thorns should check at CCTK\_PARAMCHECK to see if the correct
+coordinate system is being used for each relevant grid variable.
+While the old flesh API is still being used you may want to make this
+merely a warning.
+Use Coord\_GroupSystem() to find the coordinate system for groups (see
+section \ref{CactusBase_CoordBase_APIs}).
+
+
+\section{Coordinate APIs}
+\label{CactusBase_CoordBase_APIs}
+
+\begin{verbatim}
+int systemhandle = Coord_SystemRegister(const cGH *GH,
+                                        int dim, 
+                                        const char *systemname)
+\end{verbatim}
+registers a coordinate system, along with its
+dimension, with the CoordBase thorn.  This will create a coordinate
+system table, and return the handle of the table for success, or a
+negative error code upon error.  The possible errors are:\beforetable
+\begin{tabular}{ll}
+COORDERROR\_INVALIDDIM   & invalid dimension passed in\\
+COORDERROR\_INVALIDNAME  & invalid name passed in\\
+COORDERROR\_TABLEERROR   & error from key-value or hash tables in flesh\\
+COORDERROR\_SYSTEMEXISTS & coordinate system of this name already exists\\
+\end{tabular}
+\\These error codes are defined in CoordBase.h.  CoordBase holds the
+table handles on a GH extension, under the name ``CoordBase''.
+
+\begin{verbatim}
+int systemhandle = Coord_SystemHandle(const cGH *GH,
+                                      const char *systemname)
+\end{verbatim}
+returns the handle for a given coordinate system, or 
+negative on error:\beforetable
+\begin{tabular}{ll}
+   COORDERROR\_TABLEERROR &  error from hash table\\
+   COORDERROR\_NOSYSTEM   &  no coordinate system of this name is registered\\
+\end{tabular}
+
+\begin{verbatim}
+int coordhandle = Coord_CoordRegister(const cGH *GH, 
+                                      int systemhandle, 
+                                      int direction,
+                                      const char *coordname)
+\end{verbatim}
+registers a coordinate within a coordinate system, in the specified
+`direction'.  (Direction in this context means the index in the
+coordinate basis, which ranges from 1 to the dimension of the system.)
+Coord\_CoordRegister() returns the coordinate handle, or negative for an 
+error:\beforetable
+\begin{tabular}{ll}
+COORDERROR\_INVALIDDIM       & invalid `direction'\\
+COORDERROR\_INVALIDHANDLE    & invalid handle passed in / coordinate system
+                               does not exist\\
+COORDERROR\_TABLEERROR       & error from hash or key-value tables in flesh\\
+COORDERROR\_COORDINATEEXISTS & coordinate already exists for this `direction'\\
+COORDERROR\_DUPLICATENAME    & coordinate of this name already exists in this
+                               system\\
+\end{tabular}
+
+\begin{verbatim}
+int coordhandle = Coord_CoordHandle(const cGH *GH,
+                                    const char *coordname,
+                                    const char *systemname)
+\end{verbatim}
+returns the coordinate handle for a given coordinatate in a coordinate system,
+or negative on error:\beforetable
+\begin{tabular}{ll}
+COORDERROR\_NOSYSTEM    & no coordinate system of this name is registered\\
+COORDERROR\_TABLEERROR  & error from hash table\\
+COORDERROR\_NOSUCHCOORD & no coordinate of the name is registered for this 
+                         system\\
+\end{tabular}
+
+\begin{verbatim}
+int systemhandle = Coord_GroupSystem(const cGH *GH, 
+                                     const char *groupname)
+\end{verbatim}
+returns the handle for the coordinate system associated with a group of grid 
+variables, or negative on error.
+This can either be the default for coordinate systems of this
+dimension, or the coordinate system that is specified in the
+interface.ccl.  Coordinate systems specified in interface.ccl will
+override any defaults.  The possible error codes are:\beforetable
+\begin{tabular}{ll}
+COORDERROR\_INVALIDGROUPNAME & no such group exists\\
+COORDERROR\_NOCOORDSYS       & no coordinate system is associated with the
+                               group
+\end{tabular}
+
+\begin{verbatim}
+int systemhandle = Coord_SetDefaultSystem(const cGH *GH,
+                                          const char *systemname)
+\end{verbatim}
+sets this coordinate system to be the default for grid variables of
+the same dimension.  It returns the handle of the system, or negative
+for errors:\beforetable
+\begin{tabular}{ll}
+COORDERROR\_INVALIDNAME   & no coordinate system of this name has been 
+			    registered\\
+COORDERROR\_NODIMENSION   & coordinate system does not have a valid dimension\\
+COORDERROR\_DEFAULTEXISTS & grid variables of this dimension already have a \\
+                          & default coordinate system registered\\
+\end{tabular}
+\\There can be a default coordinate system for each grid dimension.  The
+default system will apply for each grid variable of that dimension,
+unless it is overridden.
+
+
+\section{Coordinate Schema}
+\label{CactusBase_CoordBase_coordinate_schema}
+
+\subsection{Coordinate System Tables}
+\label{CactusBase_CoordBase_system_tables}
+
+Associated with each coordinate system is a table, which should have the
+following entries:\beforetable
+\begin{tabular}{|l|l|l|}
+\hline
+\textbf{key} & \textbf{data type} & \textbf{value}\\
+\hline
+NAME        & CCTK\_STRING & \code{Cart3d|Spher3d|....}\\
+DIMENSION   & CCTK\_INT    & \code{1,2,3,...}\\
+TYPE        & CCTK\_STRING & \code{uniform|nonuniform|warped|mixed}\\
+COORDINATES & CCTK\_INT array & \verb|<coord1>,...<coord_dimension>|\\
+\hline
+\end{tabular}
+\\The values for the coordinates array are the handles for the
+coordinate tables (see section
+\ref{CactusBase_CoordBase_coord_tables}).  The NAME and DIMENSION
+fields are filled out when Coord\_SystemRegister() is called.  The
+COORDINATES field is filled out by Coord\_CoordRegister().  It is left
+for the coordinate thorn to fill out the TYPE field.
+
+\subsection{Coordinate Tables}
+\label{CactusBase_CoordBase_coord_tables}
+
+Associated with each coordinate of each coordinate system is another
+table, which should have the following entries:\beforetable
+\begin{tabular}{|l|l|l|}
+\hline
+\textbf{key} & \textbf{data type} & \textbf{values}\\
+\hline
+SYSTEM        & CCTK\_INT    & \verb|<handle>|\\
+NAME          & CCTK\_STRING & \code{x}\\
+DIRECTION     & CCTK\_INT    & \code{2}\\
+PHYSICALMIN   & CCTK\_REAL   & \code{0.0}\\
+COMPMIN       & CCTK\_REAL   & \\
+PHYSICALMAX   & CCTK\_REAL   & \\
+COMPMAX       & CCTK\_REAL   & \\
+TYPE          & CCTK\_STRING & \verb/uniform|non-uniform|warped/\\
+TIMEDEPENDENT & CCTK\_INT    & \verb/<yes (1)|no (0)>/\\
+DATATYPE      & CCTK\_STRING & \\
+GAINDEX       & CCTK\_INT    & \\
+\hline
+DELTA\footnotemark %{only for type=uniform}
+              & CCTK\_REAL   & \code{147.372e16}\\
+\hline
+\end{tabular}
+\footnotetext{only for type=\code{uniform}} 
+\\
+Coord\_CoordRegister() fills out the SYSTEM, NAME, and DIRECTION
+fields, and the COORDINATES field of the system table.  The remaining
+fields are the responsivility of the coordinate thorn.
+
+% Each of these fields should be explained...  
+% Though most are pretty self-explanatory.
+
+
+\section{Specifying coordinate systems in the interface.ccl}
+
+Coordinate systems associated with grid variable groups can be
+specified in the group's tags table, using the key \code{COORDSYSTEM}.
+Below is a grid array which could represent a vector field on a
+2-sphere.
+\begin{verbatim}
+CCTK_REAL SphericalVectorField TYPE=ARRAY DIM=2 TAGS='COORDSYSTEM="sphere2d" TENSORTYPE="vector"'
+{
+  field_theta, field_phi
+}
+\end{verbatim}
+Even though another thorn has set a default for all 2D grid variables
+to something else, Coord\_GroupSystem() will always return the handle
+for sphere2d when called on this group.
+
+% Do not delete next line
+% END CACTUS THORNGUIDE
+
+\end{document}
diff --git a/interface.ccl b/interface.ccl
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index 0000000..6133c52
--- /dev/null
+++ b/interface.ccl
@@ -0,0 +1,6 @@
+# Interface definition for thorn CoordBase
+# $Header$
+
+implements: CoordBase 
+
+include header: CoordBase.h in CoordBase.h
diff --git a/param.ccl b/param.ccl
new file mode 100644
index 0000000..c294bac
--- /dev/null
+++ b/param.ccl
@@ -0,0 +1,2 @@
+# Parameter definitions for thorn CoordBase
+# $Header$
diff --git a/schedule.ccl b/schedule.ccl
new file mode 100644
index 0000000..4160bc2
--- /dev/null
+++ b/schedule.ccl
@@ -0,0 +1,7 @@
+# Schedule definitions for thorn CoordBase
+# $Header$
+
+schedule CoordBase_Startup at CCTK_STARTUP
+{
+  LANG: C
+} "Register a GH extension to store the coordinate system handles"
diff --git a/src/CoordBase.c b/src/CoordBase.c
new file mode 100644
index 0000000..ff18a75
--- /dev/null
+++ b/src/CoordBase.c
@@ -0,0 +1,756 @@
+ /*@@
+   @file      CoordBase.c
+   @date      23 July 2003
+   @author    Gabrielle Allen and David Rideout
+   @desc 
+              Functions which implement the coordinate API.
+   @enddesc
+   @version  $Header$
+ @@*/
+
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#include "cctk.h"
+#include "util_Table.h"
+#include "util_Hash.h"
+#include "util_String.h"
+#include "CoordBase.h"
+#include "coordbaseGH.h"
+
+static const char *rcsid = "$Header$";
+
+CCTK_FILEVERSION(CactusBase_CoordBase_CoordBase_c);
+
+/********************************************************************
+ *********************  Aliased Routine Prototypes  *****************
+ ********************************************************************/
+
+/********************************************************************
+ *********************  Local Data  *********************************
+ ********************************************************************/
+
+/* table: provides master table for all coordinate systems */
+//static int tAllSystems=-1;
+/* Doesn't this do everything that we need?  What is the need for the GH extension?  Probably I should have used a GHExtension for the boundary stuff? */
+
+static unsigned int longest_coordname=0;
+static int longest_systemname=0;
+
+/********************************************************************
+ *********************  (to be Aliased?) Routines  ******************
+ ********************************************************************/
+
+ /*@@
+   @routine    Coord_SystemRegister
+   @date       24 July 2003
+   @author     Gabrielle Allen and David Rideout
+   @desc
+               Registers a coordinate system.
+   @enddesc
+   @calls      CCTK_GHExtension, Util_HashData, CCTK_VWarn, Util_TableCreate,
+               Util_TableSetString, Util_TableSetInt, Util_HashAdd
+   @calledby
+   @history
+
+   @endhistory
+   @var        GH
+   @vdesc      cctkGH *
+   @vtype      CCTK_POINTER_TO_CONST
+   @vio        in
+   @vcomment
+   @endvar
+   @var        dim
+   @vdesc      coordinate system dimension
+   @vtype      CCTK_INT
+   @vio        in
+   @vcomment
+   @endvar
+   @var        systemname
+   @vdesc      coordinate system name
+   @vtype      CCTK_STRING
+   @vio        in
+   @vcomment
+   @endvar
+
+   @returntype int
+   @returndesc
+   coordinate system handle, or:
+   COORDERROR_INVALIDDIM   invalid dimension passed in
+   COORDERROR_INVALIDNAME  invalid name passed in
+   COORDERROR_TABLEERROR   error from key-value or hash tables in flesh
+   COORDERROR_SYSTEMEXISTS coordinate system of this name already exists
+   @endreturndesc
+@@*/
+
+CCTK_INT Coord_SystemRegister(CCTK_POINTER_TO_CONST GH, CCTK_INT dim, 
+			 CCTK_STRING systemname)
+{
+  int ierr;
+  int retval;
+  int *systemhandle_ptr;
+  int systemname_length;
+  const coordbaseGH *GHex;
+  uHash *hash;
+  void *perr;
+
+  /* Initialize variables */
+  retval = 0;
+
+  /* Check input arguments */
+  if (dim <= 0)
+  {
+    retval = COORDERROR_INVALIDDIM;
+  }
+  else if (!systemname)
+  {
+    retval = COORDERROR_INVALIDNAME;
+  }
+  else
+  {
+    /* Get coordinate system name / handle hash table from GH Extension */
+    GHex = (const coordbaseGH *) CCTK_GHExtension(GH,"CoordBase");
+    hash = GHex->coordsystems;
+
+    /* Has a coordinate system of this name already been registered? */
+    systemname_length = strlen(systemname);
+    if (systemname_length>longest_systemname)
+    {
+      longest_systemname = systemname_length+1;
+    }
+    perr = Util_HashData(hash, systemname_length, systemname, 0);
+    if (perr!=NULL)
+    {
+      CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING,
+		 "Coordinate system %s already registered",systemname);
+      retval = COORDERROR_SYSTEMEXISTS;
+    }
+  }
+  
+  if (retval == 0)
+  {
+    
+    /* Now make a table for this system */
+    systemhandle_ptr = (int *) malloc(sizeof(int));
+    *systemhandle_ptr = Util_TableCreate(UTIL_TABLE_FLAGS_CASE_INSENSITIVE);
+    if (*systemhandle_ptr < 0)
+    {
+      CCTK_WARN(0,"Could not create table");
+      retval = COORDERROR_TABLEERROR;
+    }
+    else
+    {
+      retval = *systemhandle_ptr;
+    }
+
+    /* Add coordinate system name */
+    ierr = Util_TableSetString(*systemhandle_ptr, systemname, "NAME");
+    if (ierr < 0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING,
+		 "Error %d when writing coordinate system name to table",
+		 ierr);
+      retval = COORDERROR_TABLEERROR;
+    }
+
+    /* Add dimension information */
+    Util_TableSetInt(*systemhandle_ptr, dim, "DIMENSION");
+    if (ierr < 0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING,
+		 "Error %d when writing coordinate system dimension to table",
+		 ierr);
+      retval = COORDERROR_TABLEERROR;
+    }
+
+    /* Register it with the Coordinate GH Extension */
+    ierr = Util_HashAdd(hash, systemname_length, systemname, 0, 
+			  (void *) systemhandle_ptr);
+    if (ierr < 0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING,
+		 "Error %d when storing coordinate system handle",
+		 ierr);
+      retval = COORDERROR_TABLEERROR;
+    } 
+  }
+
+  return retval;
+}
+
+
+ /*@@
+   @routine    Coord_SystemHandle
+   @date       24 July 2003
+   @author     Gabrielle Allen and David Rideout
+   @desc 
+               Returns the coordinate system handle for a given name.
+   @enddesc 
+   @calls      CCTK_GHExtension, Util_HashData
+   @calledby   
+   @history 
+ 
+   @endhistory 
+   @var        GH
+   @vdesc      cctkGH *
+   @vtype      CCTK_POINTER_TO_CONST
+   @vio        in
+   @vcomment 
+   @endvar 
+   @var        systemname
+   @vdesc      coordinate system name
+   @vtype      CCTK_STRING
+   @vio        in
+   @vcomment 
+   @endvar 
+
+   @returntype int
+   @returndesc
+   coordinate system handle, or:
+   COORDERROR_TABLEERROR   error from hash table
+   COORDERROR_NOSYSTEM     no coordinate system of this name is registered
+   @endreturndesc
+@@*/
+
+CCTK_INT Coord_SystemHandle(CCTK_POINTER_TO_CONST GH, CCTK_STRING systemname)
+{
+  int *handle_ptr;
+  const coordbaseGH *GHex;
+  uHash *hash;
+
+  /* Get coordinate system name / handle hash table from GH Extension */
+  GHex = (const coordbaseGH *) CCTK_GHExtension(GH,"CoordBase");
+  hash = GHex->coordsystems;
+
+  /* Get coordinate handle from hash table */
+  handle_ptr = Util_HashData(hash, strlen(systemname), systemname, 0);
+  if (!handle_ptr)
+  {
+    *handle_ptr = COORDERROR_NOSYSTEM;
+  }
+  else if (*handle_ptr<0)
+  {
+    *handle_ptr = COORDERROR_TABLEERROR;
+  }
+
+  return *handle_ptr;
+}
+
+ /*@@
+   @routine    Coord_CoordRegister
+   @date       24 July 2003
+   @author     Gabrielle Allen and David Rideout
+   @desc
+               Registers a coordinate within a coordinate system.
+   @enddesc
+   @calls      Util_TableGetInt, CCTK_VWarn, Util_TableGetIntArray,
+               Util_TableSetIntArray, Util_TableGetString, Util_StrCmpi,
+	       Util_TableCreate, Util_TableSetInt, Util_TableSetString
+   @calledby
+   @history
+
+   @endhistory
+   @var        GH
+   @vdesc      cctkGH *
+   @vtype      CCTK_POINTER_TO_CONST
+   @vio        in
+   @vcomment
+   @endvar
+   @var        systemhandle
+   @vdesc      coordinate system handle
+   @vtype      CCTK_INT
+   @vio        in
+   @vcomment
+   @endvar
+   @var        direction
+   @vdesc      index within coodinate basis
+   @vtype      CCTK_INT
+   @vio        in
+   @vcomment   ranges from 1 to the dimension of the coordinate system
+   @endvar
+   @var        coordname
+   @vdesc      coordinate system name
+   @vtype      CCTK_STRING
+   @vio        in
+   @vcomment
+   @endvar
+
+   @returntype int
+   @returndesc
+   coordinate handle, or:
+   COORDERROR_INVALIDDIM        invalid 'direction'
+   COORDERROR_INVALIDHANDLE     invalid handle passed in / coordinate system
+                                  does not exist
+   COORDERROR_TABLEERROR        error from hash or key-value tables in flesh
+   COORDERROR_COORDINATEEXISTS  coordinate already exists for this 'direction'
+   COORDERROR_DUPLICATENAME     coordinate of this name already exists in
+                                  this system
+   @endreturndesc
+@@*/
+
+CCTK_INT Coord_CoordRegister(CCTK_POINTER_TO_CONST GH,
+			CCTK_INT systemhandle,
+                        CCTK_INT direction,
+			CCTK_STRING coordname)
+{
+  int coordinate_handle;
+  int ierr;
+  CCTK_INT system_dimension;
+  CCTK_INT *coordinate_tables;
+  CCTK_INT i;
+  char *coordname_buffer;
+
+  /* Initialize variables */
+  coordinate_handle = 0;
+  GH = GH;
+  /*(void *) ((const cGH *)GH + 0);*/
+
+  /* Check input arguments */
+  /* Get coordinate system dimension, and check for valid systemhandle */
+  ierr = Util_TableGetInt(systemhandle, &system_dimension, 
+			  "DIMENSION");
+  if (ierr<0)
+  {
+    CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Invalid system handle "
+	       "%d", systemhandle);
+    coordinate_handle = COORDERROR_INVALIDHANDLE;
+  }
+
+  /* Check for valid 'direction' */
+  if (direction<1 || direction>system_dimension)
+  {
+    CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Invalid 'direction'.  "
+	       "It but be an integer from 1 to the coordinate system "
+	       "dimension %d.", system_dimension);
+    coordinate_handle = COORDERROR_INVALIDDIM;
+  }
+
+  /* Get coordinate tables from system table */
+  coordinate_tables = (CCTK_INT *) malloc(system_dimension*sizeof(CCTK_INT));
+  ierr = Util_TableGetIntArray(systemhandle, system_dimension, 
+			       coordinate_tables, "COORDINATES");
+  if (ierr<0)
+  {
+    /* The only possibility is that this is a bad key, so add this entry */
+    for (i=0; i<system_dimension; ++i)
+    {
+      coordinate_tables[i] = -1;
+    }
+    ierr = Util_TableSetIntArray(systemhandle, system_dimension, 
+				 coordinate_tables, "COORDINATES");
+    if (ierr<0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Error adding "
+		 "coordinate tables to system table");
+      coordinate_handle = COORDERROR_TABLEERROR;
+    }
+  } 
+
+  /* Has a coordinate been registered for this 'direction'? */
+  if (coordinate_tables[direction-1]>=0)
+  {
+    CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Coordinate already "
+	       "registered for 'direction' %d", direction);
+    coordinate_handle = COORDERROR_COORDINATEEXISTS;
+  }
+
+  /* Has this coordinate name been used already in this system? */
+  coordname_buffer = (char *) malloc((longest_coordname)*sizeof(char));
+  for (i=0; i<system_dimension; ++i)
+  {
+    if (coordinate_tables[i]>=0)
+    {
+      ierr = Util_TableGetString(coordinate_tables[i], longest_coordname, 
+				 coordname_buffer, "NAME");
+      if (ierr<0)
+      {
+	CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Error reading "
+		   "coordinate name from its table");
+	coordinate_handle = COORDERROR_TABLEERROR;
+      } 
+      else if (Util_StrCmpi(coordname_buffer, coordname)==0)
+      {
+	CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Coordinate named %s "
+		   "is already registered for this system", coordname_buffer);
+	coordinate_handle = COORDERROR_DUPLICATENAME;
+	break;
+      }
+    }
+  }
+
+  /* Everything checks out */
+  if (coordinate_handle==0)
+  {
+
+    /* Is this coordinate name the longest yet? */
+    if (strlen(coordname)+1 > longest_coordname)
+    {
+      longest_coordname = strlen(coordname)+1;
+    }
+
+    /* Create coordinate table */
+    coordinate_handle = Util_TableCreate(UTIL_TABLE_FLAGS_CASE_INSENSITIVE);
+    if (coordinate_handle < 0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Could not create "
+		 "coordinate table");
+      coordinate_handle = COORDERROR_TABLEERROR;
+    } 
+    ierr = Util_TableSetInt(coordinate_handle, systemhandle, "SYSTEM");
+    ierr += Util_TableSetString(coordinate_handle, coordname, "NAME");
+    ierr += Util_TableSetInt(coordinate_handle, direction, "DIRECTION");
+    if (ierr<0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Error writing to"
+		   "coordinate table");
+      coordinate_handle = COORDERROR_TABLEERROR;
+    }
+
+    /* Register coordinate table with system table */
+    coordinate_tables[direction-1] = coordinate_handle;
+    ierr = Util_TableSetIntArray(systemhandle, system_dimension, 
+				 coordinate_tables, "COORDINATES");
+    if (ierr<0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Error writing "
+		 "coordinate table to system table");
+      coordinate_handle = COORDERROR_TABLEERROR;
+    }
+  }
+
+  free(coordinate_tables);
+  free(coordname_buffer);
+  return coordinate_handle;
+}
+
+
+ /*@@
+   @routine    Coord_CoordHandle
+   @date       25 July 2003
+   @author     Gabrielle Allen and David Rideout
+   @desc 
+               Returns the coordinate handle for a given coordinate name and 
+	       system name
+   @enddesc 
+   @calls      CCTK_GHExtension, Util_HashData, CCTK_WARN, Util_TableGetInt, 
+               Util_TableGetIntArray, Util_TableGetString, CCTK_VWarn, 
+	       Util_StrCmpi
+   @calledby
+   @history
+
+   @endhistory 
+   @var        GH
+   @vdesc      cctkGH *
+   @vtype      CCTK_POINTER_TO_CONST
+   @vio        in
+   @vcomment 
+   @endvar 
+   @var        coordname
+   @vdesc      coordinate name
+   @vtype      CCTK_STRING
+   @vio        in
+   @vcomment 
+   @endvar 
+   @var        systemname
+   @vdesc      coordinate system name
+   @vtype      CCTK_STRING
+   @vio        in
+   @vcomment 
+   @endvar 
+
+   @returntype int
+   @returndesc
+   coordinate table handle, or:
+   COORDERROR_NOSYSTEM     no coordinate system of this name is registered
+   COORDERROR_TABLEERROR   error from hash table
+   COORDERROR_NOSUCHCOORD  no coordinate of the name is registered for this 
+                             system
+   @endreturndesc
+@@*/
+
+CCTK_INT Coord_CoordHandle(CCTK_POINTER_TO_CONST GH,
+		      CCTK_STRING coordname,
+		      CCTK_STRING systemname)
+{
+  int coord_handle;
+  int *system_handle_ptr;
+  CCTK_INT system_dimension;
+  CCTK_INT *coordinate_table_handles;
+  int coordname_length;
+  int ierr;
+  int i;
+  const coordbaseGH *GHex;
+  uHash *hash;
+  char *coordname_buffer;
+
+  /* Get coordinate system name / handle hash table from GH Extension */
+  GHex = (const coordbaseGH *) CCTK_GHExtension(GH,"CoordBase");
+  hash = GHex->coordsystems;
+
+  /* Get system table handle */
+  system_handle_ptr = Util_HashData(hash, strlen(systemname), systemname, 0);
+  if (!system_handle_ptr)
+  {
+    CCTK_WARN(1, "No such coordinate system registered");
+    coord_handle = COORDERROR_NOSYSTEM;
+  }
+
+  if (system_handle_ptr)
+  {
+
+    /* Get system dimension */
+    ierr = Util_TableGetInt(*system_handle_ptr, &system_dimension, 
+			    "DIMENSION");
+    if (ierr<0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Error reading "
+		 "dimension from system table");
+      coord_handle = COORDERROR_TABLEERROR;
+    }
+
+    /* Get coordinate table handle */
+    coordinate_table_handles = 
+      (CCTK_INT *) malloc(system_dimension*sizeof(CCTK_INT));
+    ierr = Util_TableGetIntArray(*system_handle_ptr, system_dimension, 
+				 coordinate_table_handles, "COORDINATES");
+    if (ierr<0)
+    {
+      CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Error reading "
+		 "coordinate tables from system table");
+      coord_handle = COORDERROR_TABLEERROR;
+    }
+
+    /* Search for coordname */
+    coordname_length = strlen(coordname)+1;
+    coordname_buffer = (char *) malloc(coordname_length*sizeof(char));
+    for (i=0; i<system_dimension; ++i)
+    {
+      if (coordinate_table_handles[i]>=0)
+      {
+	ierr = Util_TableGetString(coordinate_table_handles[i], 
+				   coordname_length, coordname_buffer, "NAME");
+	if (ierr<0)
+	{
+	  CCTK_VWarn(0,__LINE__,__FILE__,CCTK_THORNSTRING, "Error reading "
+		     "coordinate name");
+	  coord_handle = COORDERROR_TABLEERROR;
+	}
+	else if (Util_StrCmpi(coordname_buffer, coordname)==0)
+	{
+	  coord_handle = coordinate_table_handles[i];
+	  break;
+	}
+      }
+      if (i==system_dimension-1)
+      {
+	coord_handle = COORDERROR_NOSUCHCOORD;
+      }
+    }
+
+    free(coordinate_table_handles);
+    free(coordname_buffer);
+  }
+  return coord_handle;
+}
+
+ /*@@
+   @routine    Coord_GroupSystem
+   @date       28 July 2003
+   @author     David Rideout
+   @desc 
+               Returns the coordinate system handle associated with a group of 
+               grid variables
+   @enddesc 
+   @calls      CCTK_GroupTagsTable, CCTK_VWarn, Util_TableGetString, 
+               Coord_SystemHandle, CCTK_GHExtension, CCTK_GroupIndex, 
+	       CCTK_GroupDimI
+   @calledby
+   @history
+
+   @endhistory
+   @var        GH
+   @vdesc      cctkGH *
+   @vtype      CCTK_POINTER_TO_CONST
+   @vio        in
+   @vcomment
+   @endvar
+   @var        groupname
+   @vdesc      variable group name
+   @vtype      CCTK_STRING
+   @vio        in
+   @vcomment
+   @endvar
+
+   @returntype int
+   @returndesc
+   coordinate system handle, or:
+   COORDERROR_INVALIDGROUPNAME no such group exists
+   COORDERROR_NOCOORDSYS       no coordinate system is associated with the
+                                 group
+   @endreturndesc
+@@*/
+
+CCTK_INT Coord_GroupSystem(CCTK_POINTER_TO_CONST GH, 
+		      CCTK_STRING groupname)
+{
+  int system_handle;
+  int group_tags_table;
+  int ierr;
+  int gindex; /* group index */
+  int gdim;   /* group dimension */
+  const coordbaseGH *GHex;
+  int *default_coord_systems;
+  char *system_name;
+
+  system_handle = -9999;
+
+  /* Get tags table associated with this group */
+  group_tags_table = CCTK_GroupTagsTable(groupname);
+  if (group_tags_table < 0)
+  {
+    CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Invalid group name %s",
+	       groupname);
+    system_handle = COORDERROR_INVALIDGROUPNAME;
+  }
+  else
+  {
+    /* Get associated coordinate system */
+    system_name = (char *) malloc(longest_systemname*sizeof(char));
+    ierr = Util_TableGetString(group_tags_table, longest_systemname, 
+			       system_name, "COORDSYSTEM");
+    if (ierr>=0)
+    {
+      system_handle = Coord_SystemHandle(GH, system_name);
+      if (system_handle < 0)
+      {
+	CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Coordinate system "
+		   "%s associated with group %s does not exist", system_name, 
+		   groupname);
+	system_handle = COORDERROR_INVALIDNAME;
+      }
+    }
+
+    if (system_handle == -9999)
+    {
+      /* Check for a default for all variables of this dimension */
+      GHex = (const coordbaseGH *) CCTK_GHExtension(GH,"CoordBase");
+      default_coord_systems = GHex->default_coord_systems;
+      assert(default_coord_systems);
+      gindex = CCTK_GroupIndex(groupname);
+      assert(gindex>=0);
+      gdim = CCTK_GroupDimI(gindex);
+      assert(gdim>0);
+      if ((system_handle = default_coord_systems[gdim-1]) < 0)
+      {
+	CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "No coordinate "
+		   "system is associated with group %s", groupname);
+	system_handle = COORDERROR_NOCOORDSYS;
+      }
+    }
+  free(system_name);
+  }
+
+  return system_handle;
+}
+
+ /*@@
+   @routine    Coord_SetDefaultSystem
+   @date       28 July 2003
+   @author     David Rideout
+   @desc 
+               Set this coordinate system to be the default for grid functions 
+               of the same dimension
+   @enddesc 
+   @calls      CCTK_GHExtension, Coord_SystemHandle, CCTK_VWarn, 
+               Util_TableGetInt
+   @calledby
+   @history
+
+   @endhistory
+   @var        GH
+   @vdesc      cctkGH *
+   @vtype      CCTK_POINTER_TO_CONST
+   @vio        in
+   @vcomment
+   @endvar
+   @var        systemname
+   @vdesc      coordinate system name
+   @vtype      CCTK_STRING
+   @vio        in
+   @vcomment
+   @endvar
+
+   @returntype int
+   @returndesc
+   coordinate system handle, or
+   COORDERROR_INVALIDNAME   no coordinate system of this name has been 
+                              registered
+   COORDERROR_NODIMENSION   coordinate system does not have a valid dimension
+   COORDERROR_DEFAULTEXISTS grid variables of this dimension already have a 
+                              default coordinate system registered
+   @endreturndesc
+@@*/
+
+CCTK_INT Coord_SetDefaultSystem(CCTK_POINTER_TO_CONST GH, 
+			   CCTK_STRING systemname)
+{
+  int ierr;
+  int *default_coord_systems;
+  int system_handle;
+  CCTK_INT system_dimension;
+  int retval;
+  const coordbaseGH *GHex;
+#ifdef DEBUG
+  int i;
+#endif
+
+  /* Retrieve array from GH extension */
+  GHex = (const coordbaseGH *) CCTK_GHExtension(GH,"CoordBase");
+  default_coord_systems = GHex->default_coord_systems;
+
+  /* Get coordinate system handle */
+  system_handle = Coord_SystemHandle(GH, systemname);
+  if (system_handle<0)
+  {
+    CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Invalid system name "
+	       "%s", systemname);
+    retval = COORDERROR_INVALIDNAME;
+  }
+  else
+  {
+    /* Get system dimension */
+    ierr = Util_TableGetInt(system_handle, &system_dimension, "DIMENSION");
+    if (ierr<0)
+    {
+      CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "System %s does not "
+		 "have a registered dimension", systemname);
+      retval = COORDERROR_NODIMENSION;
+    }
+    else
+    {
+      /* Set the default for this dimension */
+      if (default_coord_systems[system_dimension-1]>=0)
+      {
+	CCTK_VWarn(1,__LINE__,__FILE__,CCTK_THORNSTRING, "Default coordinate "
+		   "system for %d dimensional grid variables is already set.  "
+		   "Overwriting to %s.", system_dimension, systemname);
+	retval = COORDERROR_DEFAULTEXISTS;
+      }
+      else
+      {
+	retval = system_handle;
+      }
+      default_coord_systems[system_dimension-1] = system_handle;
+    }
+  }
+
+#ifdef DEBUG
+  for (i=0; i<system_dimension; ++i)
+  {
+    printf("def_coord_sys[%d] = %d\n", i, default_coord_systems[i]);
+  }
+#endif
+
+  return retval;
+}
diff --git a/src/CoordBase.h b/src/CoordBase.h
new file mode 100644
index 0000000..a2ec35c
--- /dev/null
+++ b/src/CoordBase.h
@@ -0,0 +1,59 @@
+/*@@
+   @header    CoordBase.h
+   @date      Wed June 26 2002
+   @author    Gabrielle Allen
+   @desc 
+   Headers and defines for coordinate base thorn
+   @enddesc 
+   @version $Header$
+ @@*/
+
+#ifndef _COORDBASE_H_
+#define _COORDBASE_H_
+
+#ifdef __cplusplus 
+extern "C" 
+{
+#endif
+
+CCTK_INT Coord_SystemRegister(CCTK_POINTER_TO_CONST GH, 
+			 CCTK_INT dim,
+			 CCTK_STRING systemname);
+
+CCTK_INT Coord_SystemHandle(CCTK_POINTER_TO_CONST GH, 
+		       CCTK_STRING systemname);
+
+CCTK_INT Coord_CoordRegister(CCTK_POINTER_TO_CONST GH,
+			CCTK_INT systemhandle,
+                        CCTK_INT direction,
+			CCTK_STRING coordname);
+
+CCTK_INT Coord_CoordHandle(CCTK_POINTER_TO_CONST GH,
+		      CCTK_STRING coordname,
+		      CCTK_STRING systemname);
+
+CCTK_INT Coord_GroupSystem(CCTK_POINTER_TO_CONST GH, 
+		      CCTK_STRING groupname);
+
+CCTK_INT Coord_SetDefaultSystem(CCTK_POINTER_TO_CONST GH, 
+			   CCTK_STRING systemname);
+
+#ifdef __cplusplus 
+}
+#endif
+ 
+#define COORDERROR_SYSTEMEXISTS     -1
+#define COORDERROR_INVALIDDIM       -2
+#define COORDERROR_INVALIDNAME      -3
+#define COORDERROR_TABLEERROR       -4
+#define COORDERROR_NOSYSTEM         -5
+#define COORDERROR_INVALIDHANDLE    -6
+#define COORDERROR_COORDINATEEXISTS -7
+#define COORDERROR_DUPLICATENAME    -8
+#define COORDERROR_NOSUCHCOORD      -9
+#define COORDERROR_INVALIDGROUPNAME -10
+#define COORDERROR_NOCOORDSYS       -11
+#define COORDERROR_NODIMENSION      -12
+#define COORDERROR_DEFAULTEXISTS    -13
+
+#endif
diff --git a/src/GHExtension.c b/src/GHExtension.c
new file mode 100644
index 0000000..1d5edea
--- /dev/null
+++ b/src/GHExtension.c
@@ -0,0 +1,164 @@
+ /*@@
+   @file      GHExtension.c
+   @date      Sun Sept 22 2002
+   @author    Gabrielle Allen and David Rideout
+   @desc 
+              CoordBase GHExtension setup
+   @enddesc 
+   @version   $Header$
+ @@*/
+
+#include <stdlib.h>
+
+#include "cctk.h"
+#include "coordbaseGH.h"
+#include "util_Hash.h"
+
+static const char *rcsid = "$Header$";
+
+CCTK_FILEVERSION(CactusBase_CoordBase_GHExtension_c);
+
+/********************************************************************
+ *********************  Scheduled Routine Prototypes  ***************
+ ********************************************************************/
+
+void CoordBase_Startup (void);
+
+/********************************************************************
+ ********************* Local Routine Prototypes *********************
+ ********************************************************************/
+
+static void *CoordBase_SetupGH (tFleshConfig *config, int conv_level, cGH *GH);
+static int CoordBase_InitGH (cGH *GH);
+
+/********************************************************************
+ *********************     External Routines   **********************
+ ********************************************************************/
+
+ /*@@
+   @routine   CoordBase_Startup
+   @date      Sunday Sept 22 2002
+   @author    Gabrielle Allen
+   @desc 
+              The startup registration routine for CoordBase.
+              Registers the GH extension needed for CoordBase.
+   @enddesc 
+   @calls     CCTK_RegisterGHExtension
+              CCTK_RegisterGHExtensionSetupGH
+	      CCTK_RegisterGHExtensionInitGH
+@@*/
+void CoordBase_Startup (void)
+{
+  int GHex_handle;
+
+  GHex_handle = CCTK_RegisterGHExtension ("CoordBase");
+  CCTK_RegisterGHExtensionSetupGH (GHex_handle, CoordBase_SetupGH);
+  CCTK_RegisterGHExtensionInitGH  (GHex_handle, CoordBase_InitGH);
+}
+
+
+/********************************************************************
+ ********************    Internal Routines   ************************
+ ********************************************************************/
+
+ /*@@
+   @routine   CoordBase_SetupGH
+   @date      Sun Sept 22 2002
+   @author    Gabrielle Allen
+   @desc 
+              Allocates CoordBase's GH extension structure
+   @enddesc 
+
+   @calls     Util_HashCreate
+
+   @var       config
+   @vdesc     the CCTK configuration as provided by the flesh
+   @vtype     tFleshConfig *
+   @vio       unused
+   @endvar
+   @var       conv_level
+   @vdesc     the convergence level
+   @vtype     int
+   @vio       unused
+   @endvar
+   @var       GH
+   @vdesc     Pointer to CCTK grid hierarchy
+   @vtype     cGH *
+   @vio       in
+   @endvar
+
+   @returntype void *
+   @returndesc
+               pointer to the allocated GH extension structure
+   @endreturndesc
+@@*/
+
+static void *CoordBase_SetupGH (tFleshConfig *config, int conv_level, cGH *GH)
+{
+  coordbaseGH *myGH;
+
+  /* suppress compiler warnings about unused variables */
+  (void) (config + 0);
+  (void) (conv_level + 0);
+  (void) (GH + 0);
+
+  /* allocate the GH extension and its components */
+  myGH = (coordbaseGH *) malloc (sizeof (coordbaseGH));
+
+  if (! myGH)
+  {
+    CCTK_WARN (0, "CoordBase_SetupGH: Unable to allocate memory for GH "
+	       "extension");
+  }
+
+  myGH->coordsystems = Util_HashCreate(8);
+
+  myGH->default_coord_systems = (int *) malloc(CCTK_MaxDim()*sizeof(int));
+
+  if (! myGH->default_coord_systems)
+  {
+    CCTK_WARN (0, "CoordBase_SetupGH: Unable to allocate memory for GH "
+	       "extension");
+  }
+
+  return (myGH);
+}
+
+ /*@@
+   @routine   CoordBase_InitGH
+   @date      28 July 2003
+   @author    David Rideout
+   @desc 
+              Initializes CoordBase's GH extension structure
+   @enddesc 
+
+   @calls     CCTK_GHExtension, CCTK_MaxDim
+
+   @var       GH
+   @vdesc     Pointer to CCTK grid hierarchy
+   @vtype     cGH *
+   @vio       in
+   @endvar
+
+   @returntype int
+   @returndesc
+               pointer to the initialized GH extension structure
+   @endreturndesc
+@@*/
+
+int CoordBase_InitGH (cGH *GH)
+{
+  const coordbaseGH *GHex;
+  int i;
+
+  /* Get the GH extension pointer again... */
+  GHex = (const coordbaseGH *) CCTK_GHExtension(GH,"CoordBase");
+
+  /* Initialize default_coord_systems to invalid table handles */
+  for (i=0; i<CCTK_MaxDim(); ++i)
+  {
+    GHex->default_coord_systems[i] = -1;
+  }
+
+  return 0;
+}
diff --git a/src/coordbaseGH.h b/src/coordbaseGH.h
new file mode 100644
index 0000000..d07ef4d
--- /dev/null
+++ b/src/coordbaseGH.h
@@ -0,0 +1,32 @@
+ /*@@
+   @header    coordbaseGH.h
+   @date      Sun Sept 22 2002 
+   @author    Gabrielle Allen
+   @desc 
+              The extensions to the GH structure from CoordBase
+   @version   $Header$
+ @@*/
+
+#ifndef _COORDBASE_COORDBASEGH_H_
+#define _COORDBASE_COORDBASEGH_H_ 1
+
+#include "util_Hash.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+typedef struct COORDBASEGH
+{
+  uHash *coordsystems;        /* Hash table mapping coord systems to tables */
+  int *default_coord_systems; /* Default coord system for each dimension */
+  /* int max_dimension;          Allocated size of default_coord_system 
+				 array (not used currently) */
+} coordbaseGH;
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif  /* _COORDBASE_COORDBASEGH_H_ */
diff --git a/src/make.code.defn b/src/make.code.defn
new file mode 100644
index 0000000..0f94373
--- /dev/null
+++ b/src/make.code.defn
@@ -0,0 +1,8 @@
+# Main make.code.defn file for thorn CoordBase
+# $Header$
+
+# Source files in this directory
+SRCS = CoordBase.c GHExtension.c
+
+# Subdirectories containing source files
+SUBDIRS =