Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site noao.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!princeton!astrovax!noao!grandi
From: grandi@noao.UUCP (Steve Grandi)
Newsgroups: net.lang.f77,net.unix
Subject: Re: Wanted: Ultra-fast fortran compiler for UNIX
Message-ID: <426@carina.noao.UUCP>
Date: Thu, 25-Jul-85 14:05:49 EDT
Article-I.D.: carina.426
Posted: Thu Jul 25 14:05:49 1985
Date-Received: Sat, 27-Jul-85 04:12:21 EDT
References: <621@astrovax.UUCP> <9871@Glacier.ARPA>
Distribution: net
Organization: Natl. Optical Astronomy Observatories, Tucson, AZ USA
Lines: 41
Xref: watmath net.lang.f77:334 net.unix:5142

> >Can anyone point to a company that supplies a UNIX Fortran compiler which
> >executes much faster than f77 (say, on par with the VMS compilers or better)?
> 
> Actually there is limited room for improvement.  The 4.2BSD compiler is
> considerably better than the original f77 in that respect.  Published
> work (by Jack Dongarra at Argonne National Laboratory
> [dongarra@anl-mcs]) shows about 25-30% slower runtimes for the 4.2BSD
> compiler over the VMS 4.1 compiler, for dense linear algebra.

Let's consider two cases.  First, pure floating point crunching as exemplified 
by the double precision LINPACK benchmark from Jack Dongarra-DONGARRA@ANL-MCS.
On a VAX-11/750 with FPA, this program compiled runs some 30% faster
on VMS (compiled with the VMS v4.1 Fortran compiler) than on 4.2BSD
Unix (with the optimizer on and with the Donn Seely f77 patches applied).

Second, let's consider the Whetstone benchmark.  For single precision
calculations, the VMS program (v3 compiler) ran 220% faster than the 4.2
program!  Why the difference between the Whetstones and the LINPACK
results?  I think the difference is largely due to the terribly
inefficient Unix math library functions: the loop

	T1=0.50025
	X=0.75
	DO 110 I=1,N11
		X=SQRT(EXP(ALOG(X)/T1))
110	CONTINUE

runs 4.9 times faster on VMS than on Unix.  4.3BSD supposedly has a
math library optimized for a VAX; let's hope so!!

Another related issue.  4.2BSD f77 with the optimizer on is VERY SLOW;
it takes about 2-4 times longer to compile a program than VMS fortran.

The bottom line is that VMS provides a significantly more efficient
Fortran system than 4.2BSD for VAXes.  Our users note the difference!
As for general software development and general timesharing, I will choose Unix
4.2BSD any day of the week over VMS; but maybe all this explains why
our 8600 runs VMS.
-- 
Steve Grandi, National Optical Astronomy Observatories, Tucson, AZ, 602-325-9228
{arizona,decvax,hao,ihnp4,seismo}!noao!grandi  noao!grandi@lbl-csam.ARPA