Cactus Code Thorn AHFinderDirect
Authors    : Jonathan Thornburg <jthorn@aei.mpg.de>
CVS info   : $Header$
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Purpose of the thorn
====================

This thorn finds an apparent horizon given the 3D xyz-grid metric and
extrinsic curvature.  It uses a direct method, writing the apparent
horizon equation as an elliptic PDE on angular-coordinate space.  This
is fast, but does require an intitial guess for the apparent horizon
position.


Documentation
=============

The doc/ directory contains a user's guide and a programmer's guide
for this thorn.


Distribution
============

This thorn should eventually become part of the CactusEinstein arrangement.

This thorn is distributed under terms of the GNU public license; see
the file COPYING in this directory for details.


Other Software Required
=======================

* This thorn requires the Einstein thorn.
* This thorn is written in C++, so you'll need a C++ compiler to compile
  this thorn.  It calls various C and Fortran numerical libraries; if
  these aren't already installed on your system, then you'll need C
  and Fortran compilers to compile them.
* Most of this thorn's relativity code is machine-generated using Maple
  (version 6), but you don't need Maple unless you want to modify the
  relativity code.


Portability
===========

This thorn is known to compile and run successfully on the following
systems:
* Red Hat GNU/Linux, gcc 2.95.3
* Alpha OSF1 V4.0, gcc 2.95.3