--- manual/s_phys_pkgs/text/exch2.tex 2004/05/10 21:39:11 1.19 +++ manual/s_phys_pkgs/text/exch2.tex 2005/06/10 19:34:09 1.23 @@ -1,4 +1,4 @@ -% $Header: /home/ubuntu/mnt/e9_copy/manual/s_phys_pkgs/text/exch2.tex,v 1.19 2004/05/10 21:39:11 afe Exp $ +% $Header: /home/ubuntu/mnt/e9_copy/manual/s_phys_pkgs/text/exch2.tex,v 1.23 2005/06/10 19:34:09 afe Exp $ % $Name: $ %% * Introduction @@ -215,12 +215,20 @@ The number of tiles MITgcm allocates and how they are distributed between processors depends on \varlink{nPx}{nPx} and \varlink{nSx}{nSx}. \varlink{nSx}{nSx} is the number of tiles per -processor and \varlink{nPx}{nPx} is the number of processors. The total -number of tiles in the topology minus those listed in -\file{blanklist.txt} must equal \code{nSx*nPx}. Note that in order to +processor and \varlink{nPx}{nPx} is the number of processors. The +total number of tiles in the topology minus those listed in +\file{blanklist.txt} must equal \code{nSx*nPx}. Note that in order to obtain maximum usage from a given number of processors in some cases, -this restriction might entail sharing a processor with a tile that would -otherwise be excluded. \\ +this restriction might entail sharing a processor with a tile that +would otherwise be excluded because it is topographically outside of +the domain and therefore in \file{blanklist.txt}. For example, +suppose you have five processors and a domain decomposition of +thirty-six tiles that allows you to exclude seven tiles. To evenly +distribute the remaining twenty-nine tiles among five processors, you +would have to run one ``dummy'' tile to make an even six tiles per +processor. Such dummy tiles are \emph{not} listed in +\file{blanklist.txt}.\\ + The following is an example of \file{SIZE.h} for the twelve-tile configuration illustrated in figure \ref{fig:12tile} running on