Import new thorn InitBase.

Thorn InitBase specifis how initial data are to be set up.  It does
not set up any initial data by itself, not does it contain any
routines which are to be called.  It is merely a convenient repository
remembering how initial data are to be set up, so that other thorns
can check their actions against this thorn.


git-svn-id: http://svn.cactuscode.org/arrangements/CactusBase/InitBase/trunk@2 7add7b9e-bd1d-4575-9a9f-c44cbffd177e

1 files changed, 31 insertions, 0 deletions

diff --git a/README b/README
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+Cactus Code Thorn InitBase
+Thorn Author(s)     : Erik Schnetter <schnetter@cct.lsu.edu>
+Thorn Maintainer(s) : Erik Schnetter <schnetter@cct.lsu.edu>
+--------------------------------------------------------------------------
+
+Purpose of the thorn:
+
+Thorn InitBase specifis how initial data are to be set up.  It does
+not set up any initial data by itself, not does it contain any
+routines which are to be called.  It is merely a convenient repository
+remembering how initial data are to be set up, so that other thorns
+can check their actions against this thorn.
+
+There are several possibilities:
+
+1. The initial data thorn sets up data on one time level, while other
+   time levels are scratch space.  The time evolution method must
+   start up from a single time level.  (This is the default.)
+
+2. The initial data thorn sets up data on exactly one time level, and
+   is called once for each active time level.  (This means that the
+   initial data thorn can only access the current time level.)
+
+3. The initial data thorn sets up data on exactly two time levels, and
+   is called once for each active time level.  (This means that the
+   initial data thorn can only access the current and the first past
+   time level.)
+
+4. The initial data thorn sets up data on all active time levels.
+   (This makes it necessary that the initial data thorn checks the
+   number of active time levels.)