Apply Frank Loeffler's patch to improve the processor distribution of

PUGH:

Up to now, PUGH does not take the actual grid size into account while
setting the number of processors/domains in each direction.  This
gives problems, e.g. using boxes like 200x7x7 (with 3 ghostzones).  It
also does not really do a good job in situations with non near-cubic
domains (like in bitant mode it devides first in the z-direction,
which is usually the smallest).

I inserted another decomposition algorithm which is looking for the
longest direction and devides this if possible.  Because it was done
to be easy to understand, it can fail in certain situations, in which
it is gracefully falling back to the old decomposition (e.g. a cubic
box and 9 processors).

To include this algorithm I added a keyword "automatic_old" to
PUGH::processor_topology.  The new behaviour is the default; this
keyword re-enables the old behaviour.


git-svn-id: http://svn.cactuscode.org/arrangements/CactusPUGH/PUGH/trunk@471 b61c5cb5-eaca-4651-9a7a-d64986f99364

1 files changed, 9 insertions, 0 deletions

diff --git a/doc/documentation.tex b/doc/documentation.tex
index 4f9abac..53aed8d 100644
--- a/doc/documentation.tex
+++ b/doc/documentation.tex
@@ -166,6 +166,15 @@ the partition parameters) will apply the automatic distribution. That's why
 it is not necessary to set \verb|PUGH::partition_3d_y = "30"| or
 \verb|PUGH::partition_3d_z = "15 15"| in the parameter file.
 
+Because the previous automatic distribution gave problems in some
+cases (e.g.\ very long box in one, but short in other directions),
+there is now an improved algorithm that tries to do a better job in
+decomposing the grid evenly to the processors.  However, it can fail
+in certain situations, in which it is gracefully falling back to the
+previous (\verb|"automatic_old"|) giving a warning.  Note that, if one
+or more of the parameters \verb|PUGH::processor_topology_3d_*| or
+\verb|PUGH::partition_3d_*| are set, this mode automatically falls back to
+\verb|"automatic_old"| without warning.
 
 \section{Understanding PUGH Output}