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PSTSWM on the Cray X1

Compiler and Page Size Comparisons

The runtime environment on the X1 allows the user to choose among a number of different page sizes to use when executing a job. Three of the four curves in the following graphs represent the single processor performance when executed with 16 MByte pages. The curves describe performance when the code is compiled with

-Ostream2, vector2, scalar2 (def)
-Oaggress,stream2,vector2,scalar2 (agg1)
-Oaggress,stream3,vector3,scalar3 (agg2)

optimization. The fourth curve uses the agg2 optimization and 64 KByte pages. Note that we did not collect data for the largest horizontal resolutions for agg2 with 64 KByte pages. Also note that the maximum horizontal resolution decreases as the number of vertical levels increases. A single process is limited to 8 GBytes of memory currently.

From these results, the default and more aggressive optimizations are equally good for all problem sizes when using 16 MByte pages, and performance grows with both horizontal resolution and number of vertical levels. In contrast, when running with 16 KByte pages, performance starts degrading once the problem size exceeds T85 for one vertical level and T42 for the problems with larger numbers of vertical levels.

URL: http://www.csm.ornl.gov/evaluation/PHOENIX/PSTSWM-compiler.CRAYX1.html
Updated: Thursday, 19-Jun-2003 13:07:12 EDT
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