PSTSWM AlphaSC-1000 Serial Performance

Performance Studies using

PSTSWM

Date/Person:	January 4, 2002 / Patrick H. Worley
Platform:	Compaq AlphaServer SC at Pittsburgh Supercomputer Center (lemieux.psd.edu):
	760 ES45 4-way SMP nodes (1 GHz Alpha 21264C with 8MB L2 cache)
Environment:	Compaq Tru64 UNIX V5.1A
	Compaq Fortran Compiler X5.4A-1684-46B5P
Code Version:	6.8.2
Make Options
T5, T10:	MACH=alpha-sc COMM=mpi PRECISION=8 PERF=n WORKSPACE=20000000 MATH=portable
T21, T42, T85, T170:	MACH=alpha-sc COMM=mpi PRECISION=8 PERF=n WORKSPACE=20000000 MATH=cxml
Compilation Options:	f90 -O4 -assume accuracy_sensitive -math_library accurate -align dcommons -align records -arch host -tune host
Number of steps:	T5, T10, T21, T42: 241 or 481
	T85: 49 or 97
	T170: 49 or 97
Number of processors per node:	1, 2, 3, or 4
Notes:	using CXML library routines for Fourier transforms and BLAS

T5 MFlop rates

Per Processor Rate

Per Node Rate

**T5 MFlop rates**
Per Processor Rate	Per Node Rate

T10 MFlop rates

Per Processor Rate

Per Node Rate

**T10 MFlop rates**
Per Processor Rate	Per Node Rate

T21 MFlop rates

Per Processor Rate

Per Node Rate

**T21 MFlop rates**
Per Processor Rate	Per Node Rate

T42 MFlop rates

Per Processor Rate

Per Node Rate

**T42 MFlop rates**
Per Processor Rate	Per Node Rate

T85 MFlop rates

Per Processor Rate

Per Node Rate

**T85 MFlop rates**
Per Processor Rate	Per Node Rate

T170 MFlop rates

Per Processor Rate

Per Node Rate

**T170 MFlop rates**
Per Processor Rate	Per Node Rate

The performance discrepancy here indicates the cost of contention for memory (bandwidth) when multiple processors are running simultaneously. The total memory required per node goes up as the number of processors increases, but the per processor cache behavior and memory access patterns is constant.
This experiment indicates the difference in performance one might see in a space sharing context, sharing the node with other users, or in a scaled speed-up experiment, where the size of a parallel job is increased as the number of processors used increases.
Note that two different metrics are displayed - per processor computational rate and per node computational rate. The per node rate is the best measure of the performance of the architecture, but the per processor rate is a convenient way to observe performance degradation.