

On the QMD code I use, this the the approx performance table:
(single cpu times only)

cpu		OS 		time (in seconds) per time step
---------------------------------------------------------------
486/DX33	OS/2 Warp	3000  (memory starved at 8 meg)
R3000/40MHz	IRIX 5.3	900
SuperSparc/33MhzSolaris		700
Pentium/133MHz	OS/2 Warp	290  (64 Meg ram)
R4400/150MHz	IRIX 5.3	126  (Indy w 96 meg ram)
RS6000/590	AIX		120
Cray J90	Unicos		87 
Alpha/266	OSF1		82
R8000/75MHz	IRIX 6.1	55   (2 meg cache, 384 meg ram)
R8000/90MHz	IRIX 6.1	47   (4 meg cache, 2 gig ram)
(no data on R10k ... yet :-) )

64 atom supercell, same configuration and input file on all machines.

THe fortran compiler on the PC was the Watcom 9.01e, and the
combination of gcc/emx and f2c (which did quite well).

The Pentium unit is my advisors home PC that we are using for additional 
cycles for the rest of the group.

THe R8k times are low as a result of my optimizing the time consuming 
portions of the code to make use of fused multiply add instructions and 
working very hard to get a good instruction scheduling out of the compiler.

I used a 64 atom supercell as my standard test as that is what I tend to 
work with.  When I go to larger supercells, all but the largest memory 
machines quit. At 512 atoms, even the powerchallenge is spending 
more time swapping (with 4 GB ram installed) than computing.

My thoughts are that the Pentium133 and higher with sufficient ram and a 
FAST disk (the current crop of ATA4 are not as fast as SCSI II) ought to 
be a good cheap entry level workstation for development and testing 
work.  I prefer an Indy, but I think I am biased (see the .sig).  
For the production medium and big runs, you really do need to look at the 
heavy metal (the superworkstations).  Run a stable OS on the box such as 
Linix or OS/2 Warp Connect and the machine will be very useful.

Joe

From: "Walter E. Reiher III" <[email-masked]>

Related issues have been raised here before, so I'm responding to the list:

I've spent an inordinate amount of time over the past year and a half or so
fiddling around with PC FORTRAN compilers, and the bottom line, IHMO, is
that you'd better not count on them being like what you're accustomed to
under UNIX.  In general, PCs seem like a false economy to me.

There are two issues here:  the compiler and the operating system.

You don't mention which OS you're using, but MS FPS only runs under NT or
Win95.  If you're running Win95, or DOS/Win, that's the first thing to get
rid of.  Windows NT is a reasonable OS; many say OS/2 is also.  There are
also UNIXes available for Intel CPUs.  Just don't waste your time with a 16
bit OS like DOS or a hybrid 16/32 system like 95.
     Many 'big program' problems are related to trying to run in 16 bits or
tricking a 16 bit OS into looking like a 32 bit one.  How long has it been
since we're tried doing this with UNIX?  Years!  Who needs to go back to _that_?

On compilers, I've worked with three--Watcom, MS FORTRAN PowerStation 32
(predecessor to 4.0), and Absoft--and all of them have some problems for my
applications, which involve mixed FORTRAN and C programming and
interoperability with a MS Visual C++ graphics DLL.  Watcom had loads of
incompatibility problems and really poor tech support, but produces fast
code when you can make it work.  MS FPS also produces fast code and has a
nice development environment, but has surprisingly poor interoperability
with C.  I'm continuing to use Absoft, who has excellent tech support and C
interoperability but produces slow code on a Pentium and has some other quirks.
     Other compiler vendors I have not tried include Salford (a British
company; expensive compiler but it must be a 'real' one since all of Chem-X
builds under it), Microway NDP, and Lahey.
     BTW, I've only used these as FORTRAN 77's, not 90's.

If you don't need to worry about working with C and calling DLLs, life will
probably be easier for you.  It seems to me that FORTRAN really isn't taken
seriously by the compiler vendors--the emphasis is on C/C++.
     I was disappointed to learn this week that the FORTRAN on my
'reference' platform, the SGI, also isn't what it used to be.  Some switches
that I found valuable for finding bugs in old code on my old IRIX 5.2 system
are missing on my new IRIX 6.1 system (e.g., -trapuv and -u).

See the "SciTech Software for Science" catalog for a comprehensive list of
FORTRAN compilers and other technical software tools.  800-622-3345,
http://www.scitechint.com/scitech/.  I'm not affiliated with them.

Hope this helps...good luck.  I'd be interested in hearing the experiences
of others.

Wally
========================================================================
Walter E. Reiher III, Ph.D.                           [email-masked]
CompChem Innovations
P.O. Box 61056                                        voice 408-720-0240
Sunnyvale, CA 94088                                     fax 408-720-0378

From: Craig Taverner <[email-masked]>

We use PC's as computational tools extensively in crystallography, but we 
run them all (the computational ones that is) under LINUX for which f77 
is freely available (g77 and f2c), and we also have the NAG f90 compiler, 
which so far seems to compile fine with true fortran 90 programs, but has 
proved to be somewhat tricky with fortran 77 programs.  Unfortunately I 
have not used it nearly enough to give you any performance spec.'s or say 
whether it can cope with very large programs, but I should certainly 
expect it to be able to.

So far our experience with using Linux instead of Dos/windows has 
definitely demonstrated it to be more appropriate for computational 
work.

Contact NAG at:
           NAG Ltd                 NAG Inc
tel        +44 (0)1865 311744      +1 708 971 2345
fax        +44 (0)1865 311755      +1 708 971 2346
post       NAG Response Centre     NAG Response Center
           NAG Ltd                 NAG Inc
           Wilkinson House         1400 Opus Place
           Jordan Hill Road        Suite 200
           OXFORD                  Downers Grove
           United Kingdom          IL 60515-5702
           OX2 8DR                 USA
email      [email-masked]      [email-masked]
www        http://www.nag.co.uk
gopher     NAME=NAG Gopher Server, Type=1, Port=70, Path=1/,
           Host=www.nag.co.uk

This is straight from their magazine, verbatum.  I hope it's not 
overboard.

Cheers, Craig

"If God had meant us to be naked, we would have been born that way."

Craig Taverner
Structural Chemistry, University of the Witwatersrand, South Africa

From: Guo Jian-xin <[email-masked]>

Hi,
   Your question about the compiler maybe get:
The NDP fortran compiler is good as the microft fortran complier. It is a
 better choice.
regards,
J.X. Guo

From: [email-masked] (Frits Daalmans)

hello,

I think that NAG (Numerical Algorithms Group) sells a Fortran 90 compiler 
for Linux.
Lemmesee...
no, sorry, I don't have more information.

Greetings,
Frits

Frits Daalmans
OIO Conformational Analysis
Gorlaeus Laboratoria
Leiden, The Netherlands
E-mail: [email-masked]
Tel: [+31] (0)71-5274505

From: [email-masked]

Yeah, it is FORTRAN 90, maybe it's NAG.
If it is not YAG, I will tell you after I asked my friend.

Jochen

From: [email-masked] (Richard Walsh)

Taisung,

You should try Absoft at 810-853-0050 (www.absoft.com). They have 
F77 and F90 for PC. Their F90 is compatible with the F90 on Cray
platforms so you codes should compile error free on either machine.
The same F90 is available for SUNs and I will be made available
for other workstations in the future.

Richard Walsh
Minnesota Supercomputer Center, Inc.

P.S. They also have compilers for Macs I think.

From: [email-masked] (David Case)

I'd be interested to know what sorts of errors you encountered, and on
which OS.  Do the errors show up in F77 code, or in the F90-specific parts?
I have used this compiler on a P6/NT machine with good success on very
large F77 molecular mechanics programs.

 ..thx...dac

==================================================================
David A. Case                    |  internet:    [email-masked]
Dept. of Molecular Biology, MB1  |  bitnet: case%scripps.edu@sdsc
The Scripps Research Institute   |  fax:             619-554-3789
10666 N. Torrey Pines Rd.        |  phone:           619-554-9768
La Jolla CA 92037  USA           |  WWW:  http://scripps.edu/case
==================================================================

From: [email-masked] (Randy Zauhar)

To: Taisung Lee <[email-masked]>
Subject: Re:  CCL:Good Fortran Compiler for computational science on PC?
--------------------
   Taisung,

      There is a company called Lahey (in Nevada, I believe) that specializes
  in FORTRAN compilers for PCs. I investigated their products a few years 
  ago and was favorably impressed with what they offered, although I did not
  end up buying anything from them. They use to regularly have ads in BYTE
  magazine. If you cannot find their address, I think I still have some of 
  their literature laying around. 

        Randy

All opinions expressed here are mine, not my employer's

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