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+%version   $Header$
+\documentclass{article}
+\begin{document}
+
+\title{PUGHInterp}
+\author{Paul Walker, Thomas Radke, Erik Schnetter}
+\date{1997-2001}
+\maketitle
+
+\abstract{Thorn PUGHInterp provides interpolation of arrays
+          at arbitrary points.}
+
+\section{Purpose}
+Thorn PUGHInterp implements interpolation operators working on regular,
+uniform cartesian grids. They can be applied to interpolate both CCTK grid
+variables (grid functions and arrays distributed over all processors), and
+processor-local arrays at arbitrary points.\\
+The operators for distributed/local arrays are invoked via the flesh
+interpolation API routines {\tt CCTK\_InterpGV()} and {\tt CCTK\_InterpLocal()}
+resp. They are registered with the flesh under the name {\it ''uniform
+cartesian''} prepended by the interpolation order (eg. {\it ''second-order
+uniform cartesian''}). Currently there is first, second, and third-order
+interpolation implemented.\\
+
+\section{Implementation Notes}
+The interpolation operators registered for different orders are mapped
+via wrappers (in {\tt Startup.c}) onto a single routine (in {\tt Operator.c})
+just passing the order as an additional argument.\\
+The routine for distributed arrays will then map all points to interpolate
+at to the processors which own those points, and communicate the points'
+coordinates and corresponding input arrays ({\tt MPI\_Alltoall()} is used
+for this).\\
+Then the interpolation takes place in parallel on every processor, calling
+a core interpolation routine (located in {\tt Interpolate.c}). This one
+takes a list of input arrays and points and interpolates these to a
+list of output arrays (one output value per interpolation point).\\
+Again, for distributed arrays, the interpolation results for remote points
+are sent back to the requesting processors.\\[2ex]
+%
+Current limitations of the core interpolation routine's implementation are:
+%
+\begin{itemize}
+  \item arrays up to three ({\bf MAXDIM}) dimensions only can be handled
+  \item interpolation orders up to three ({\bf MAXORDER}) only are supported
+  \item coordinates must be given as {\bf CCTK\_REAL} types
+  \item input and output array types must be the same
+        (no type casting of interpolation results supported)
+\end{itemize}
+%
+Despite of these limitations, the code it was programmed almost generic
+in that it can easily be extended to support higher-dimensional arrays
+or more interpolation orders.\\
+Please see the NOTES in this source file for details.
+
+\section{Comments}
+%
+For more information on how to invoke interpolation operators please refer
+to the flesh documentation.
+%
+% Automatically created from the ccl files 
+% Do not worry for now.
+\include{interface}
+\include{param}
+\include{schedule}
+
+\end{document}