Changes between Version 5 and Version 6 of Things To Do

Timestamp:

01/25/10 10:02:21 (16 years ago)

Author:

Stephen Siegel

Comment:

--

Things To Do

@@ -42 +42 @@
  * Diffusion
     * What does the distribution strategy do if the number of cells is less than the number of procs?  Does it necessarily place two consecutive cells on two consecutive procs?  If it does not, then how can the ghost cell exchange work?   The exchange routine assumes that the neighboring cells will be on neighboring procs.   Check this out.
-    * Interestingly, the parallel version is not necessarily correct when the number of cells is less than the number of processes.   It is possible for there to be a process  "gap" between two consecutive cells.  But you need at least 5 procs in order to see this.   Added {{{Diffusion_5_2_5_Test.java}}} to demonstrate this.
+    * Interestingly, the parallel version is not necessarily correct when the number of cells is less than the number of processes.   It is possible for there to be a process  "gap" between two consecutive cells.  But you need at least 5 procs in order to see this.   Added {{{Diffusion_5_2_5_Test.java}}} to demonstrate this.  The fix: just change the way the neighbor ranks are computed (left/right, upper/lower).  These should be computed using the {{{owner}}} function to find out the rank of the process that owns the row next to you, instead of just assuming this will be your rank +/- 1.