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From: sra@oddjob.UUCP (Scott R. Anderson)
Newsgroups: net.lang.f77,net.unix
Subject: Re: Wanted: Ultra-fast fortran compiler for UNIX
Message-ID: <867@oddjob.UUCP>
Date: Tue, 23-Jul-85 10:31:27 EDT
Article-I.D.: oddjob.867
Posted: Tue Jul 23 10:31:27 1985
Date-Received: Thu, 25-Jul-85 06:03:21 EDT
References: <621@astrovax.UUCP> <9871@Glacier.ARPA> <624@astrovax.UUCP>
Reply-To: sra@oddjob.UUCP (Scott R. Anderson)
Organization: University of Chicago, Department of Physics
Lines: 29
Xref: watmath net.lang.f77:333 net.unix:5116
Summary: 

In article <9871@Glacier.ARPA> conor@Glacier.UUCP (Conor Rafferty) writes:

>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.

I have a copy of Jack Dongarra's Technical Memorandum No. 23 (dated
July 18, 1985) which was passed around at a recent conference here
on high-performance computing.  For those who are interested, here
are the results of solving a linear system of equations of order
100 with LINPACK on a VAX 11/780 with FPA:

Precision    Operating System    MFLOPS    Time (sec)    Unit (usec)
---------    ----------------    ------    ----------    -----------

Double         VMS v4.1           0.14        4.96          14.4
               UNIX 4.2BSD        0.13        5.67          16.5

Single         VMS v4.1           0.25        2.74          7.98
               UNIX 4.2BSD        0.21        3.25          9.47

(Unit is the execution time for the statement y(i) = y(i) + t * x(i).)

These results verify that the UNIX f77 compiler is not as efficient
as the VMS fortran compiler, but the "slowness" factor is actually
14-19%, not 25-30%.

				Scott Anderson
				ihnp4!oddjob!kaos!sra