Subject: Re: Seeking words of wisdom <[email-masked]>

From: Roberto Gomperts <[email-masked]>
Date: Tue, 24 Aug 93 08:23:22 EDT

Your message dated: Wed, 18 Aug 93 13:33:45 EDT
|>  In response to:
|>  >I am wondering what a good investment could be. That is, we have words
|>  >that a mini-CRAY is in the market, and that HP-750 workstations can
|>  >give about half the speed of a real CRAY
|>  
|>  Dr. Omar G. Stradella responds:
|>  >>You should also consider the new line of symmetric multiprocessors from
|>  >>Silicon Graphics, the Power Challenge Series. 
|>  >> ... 
|>  >>...   (deleted specs and peak speed info for sgi and cray boxes)
|>  
|>  There are a lot of wonderful new machines out there but info on
|>  advertised peak speeds is nearly worthless in distinguishing between
|>  them.  Information on sustained performance on a typical problem
|>  using Gaussian92, GAMESS, etc. is helpful to this audience.  
|>  Actually, a few typical cases which differ in the vectorization
|>  of the code used (SCF, gradient, CI, etc) is even better since that
|>  shows the effects of differing cache designs.
|>  
|>  Is any info on the Power Challenge Series, Cray desk(top/side), etc
|>  compared to garden variety risc boxes available out there?
|>  
|>  Don Phillips
|>

Dear netters,
  
Since this has been explicitly asked I will post at the end of this message a 
table with timings for a set of jobs ran and posted originally by  Richard 
Walsh comparing Cay C90 execution times with PC times. My table compares the 
currently available SGI-Challenge systems running at 100/50 MHz and 150/75 MHz 
with the C90 timings from Richard Walsh.
But first some clarifications/confirmations:
As Michael Frisch and Mark Berger stated, Gaussian 92 has been certified for the 
Challenge and Onyx series running IRIX 5.0 (and higher). The first certified 
version was D.2. 
Power Challenge is a system that will be available beginning of next year, so
obviously Gaussian has not been certified on this machine. However, barring any
catastrophic events, Gaussian should be submitted for certification on the Power
Challenge shortly after the final version of the OS and Compilers have been firmed
up.
Also, as Richard Walsh suggested, the Power Challenge will be binary compatible with 
the current Challenge, i.e. executables build for the Challenge/Onyx systems will 
run correctly on the Power Challenge. The drawback is that not all of the 
potential performance of the new machine will be utilized.

Please feel free to contact Mark Mark Berger or myself if further 
clarification/informaton is needed.

				-- Roberto

						Roberto Gomperts
						[email-masked]
						phone: (508) 562 4800
						Fax:   (508) 562 4755

"Gracias a la vida,
que me ha dado tanto ..."
        Violeta Parra

                                                April/May 1993

Gaussian 92 rev D.2

Results for Challenge 100/50 MHz.
=================================

Summary.
=======
A number of "typical" Gaussian calculations have been performed on
different number of processors and with different memory usage on the
new SGI "Challenge" computer running at 100/50 MHz and 150/75MHz.
When available comparisons are made with a Cray C90.
Some preliminary conclusions.
  . Very small differences between CPU time and Wall Clock time,
  degradation is in general less than 3%
  . Minimal degradation when running throughput using all available
  processors (less than 3%)
  . Comparison with Cray C90: 1 processor runs can be as much a 25x
  slower than the C90, but 12 processor runs can be only 3.5x slower
  than the Cray
  . Differences between Direct and In-core calculations on the Challenge
  are not as big as in the Cray. Average ratio for the Cray is: 2.5x,
  for the Challenge (1 processor): 1.68x. This ratio becomes even
  smaller on the Challenge when parallelism is used: In-core speed-ups
  are poorer than Direct SCF speed-ups.

NEW
===
I ran the tests on a 4 processor Challenge running at 150/75 MHz. This
machine had smaller memory so instead of 16MW I used 12MW (== 96 MBytes)
for the large calculations.

Test 1
======
Test 178 from Gaussian's QA suite:
Single Point Direct SCF calculation: 300 basis sets, extensive
Population Analysis
* Increased memory to 16 MW (== 128 MBytes)

Times in minutes
                100/50 MHz                    150/75 MHz
proc  CPU   SpUp    C90fr   WClock      CPU   SpUp    C90fr
 1    103 ( 1.00)    4.1%    105         69 ( 1.00)    6.2%
 2     56 ( 1.83)    7.6%     57         38 ( 1.81)   11.2%
 4     31 ( 3.32)   13.8%     32         21 ( 3.28)   20.3%
 8     19 ( 5.42)   22.5%     20         13 ( 5.31)   32.9%
12     15 ( 6.86)   28.5%     16         10 ( 6.90)   42.8%

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor
C90fr:  Percentage of a Cray C90. Base time of C90:  4.28 min CPU time
WClock: Wall Clock Time.

I ran 5 simultaneous copies of this job each using 4 MW (== 32 MBytes) of
memory and 4 processors, on a 20 processor challenge.
CPU time of slowest job: 33 min
Wall Clock time for completion of all jobs: 34 min.

Test2
=====
Skeleton of test178 of Gaussian's QA suite. Changed to become a Force
calculation with standard Population Analysis. Command line:
#P RHF/6-31G** scf=direct force

* Increased memory to 16 MW (== 128 MBytes)

This test gives an idea of the to be expected performance of geometry
optimizations of large molecular systems.

Times in minutes
          100/50 MHz            150/75 MHz
proc  CPU   SpUp     WClock     CPU   SpUp
 1    339 ( 1.00)     344       229 ( 1.00)
 2    181 ( 1.87)     186       123 ( 1.86)
 4     96 ( 3.53)      99        69 ( 3.31)
 8     55 ( 6.16)      58        38 ( 6.02)
12     42 ( 8.07)      44        28 ( 8.17)
16                               24 ( 9.54)
20                               21 (10.90)

Test3
=====
RHF/6-31G* Frequencies on propellane: 87 basis functions.

A) Using 4 MW ( == 32 MBytes) SCF is NOT in-core
Times in minutes
proc  CPU   SpUp    C90fr   WClock
 1     48 ( 1.00)    8.9%     49
 2     25 ( 1.92)   17.1%     26

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor
C90fr:  Percentage of a Cray C90. Base time of C90:  4.29 min CPU time
WClock: Wall Clock Time.

B) Using 16 MW ( == 128 MBytes) SCF is in-core
Times in minutes
          100/50 MHz                  150/75 MHz
proc  CPU   SpUp    C90fr       CPU   SpUp    C90fr   
 1   27.8 ( 1.00)    5.3%      19.1 ( 1.00)    7.7%
 2   16.8 ( 1.65)    8.8%      11.5 ( 1.66)   12.8%
 4   10.5 ( 2.64)   14.1%       7.2 ( 2.65)   20.5%
 8    7.3 ( 3.81)   20.2%
12    6.3 ( 4.41)   23.4%

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor
C90fr:  Percentage of a Cray C90. Base time of C90:  1.48 min CPU time

Test4
=====
RMP2/6-31G* Single point energy on acetone: 72 basis functions

A) Using 2 MW ( == 16 MBytes) SCF is NOT in-core
Times in seconds
                100/50 MHz
proc  CPU   SpUp    C90fr   WClock
 1    339 ( 1.00)   12.8%    343
 2    266 ( 1.27)   16.2%    272
 4    231 ( 1.46)   18.7     243

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor
C90fr:  Percentage of a Cray C90. Base time of C90:  43.27 sec CPU time

B) Using 16 MW ( == 128 MBytes) SCF is in-core
Times in seconds
          100/50 MHz               150/75 MHz
proc  CPU   SpUp    C90fr     CPU   SpUp    C90fr  
 1    157 ( 1.00)    9.7%     103 ( 1.00)   14.7%
 2    122 ( 1.28)   12.4%      83 ( 1.24)   18.3%
 4    108 ( 1.45)   14.1%      72 ( 1.43)   21.1%

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor
C90fr:  Percentage of a Cray C90. Base time of C90:  15.23 sec CPU time

Test5
=====
RMP4/6-31G* Single point energy on acetaldehyde: 53

Using 4 MW ( == 32 MBytes) SCF is in-core
Times in seconds
                100/50 MHz                 150/75 MHz
proc  CPU   SpUp    C90fr   WClock
 1    690 ( 1.00)    9.2%    706
 2    452 ( 1.52)   13.9%    465
 4    324 ( 2.13)   19.4%    344
 8    266 ( 2.59)   23.6%    299
12    242 ( 2.85)   26.0%    283

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor
C90fr:  Percentage of a Cray C90. Base time of C90:  62.94 sec CPU time

Test6
=====
RHF/6-31+G CI-Singles excited states on benzene: 90 basis functions

A) Using 2 MW ( == 16 MBytes) SCF is NOT in-core
Times in seconds
                100/50 MHz                150/75 MHz
proc  CPU   SpUp    C90fr   WClock     CPU   SpUp    C90fr
 1    908 ( 1.00)    9.7%    924       600 ( 1.00)   14.7%
 2    753 ( 1.20)   11.7%    783       480 ( 1.25)   18.3%
 4    652 ( 1.39)   13.5%    685       420 ( 1.42)   21.0%
 8    587 ( 1.54)   15.0%    619
12    587 ( 1.54)   15.0%    647

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor
C90fr:  Percentage of a Cray C90. Base time of C90:  88.23 sec CPU time

B) Using 16 MW ( == 128 MBytes) SCF is in-core
Times in seconds
      100/50 MHz       150/75 MHz
proc  CPU   SpUp       CPU   SpUp
 1    823 ( 1.00)      540 ( 1.00)
 2    713 ( 1.15)      480 ( 1.12)
 4    652 ( 1.26)      420 ( 1.28)

proc:   Number of processors
CPU:    user+system cpu time
SpUp:   Speed Up with respect to 1 processor

(*) This test case gives different number of SCF cycles for varying
number of processors and memory sizes (between 13 and 19 cycles). All
results are consistent however at all levels: RHF, MP2 and CIS.

                                                Roberto Gomperts