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From: lel@wuphys.UUCP
Newsgroups: net.micro.amiga
Subject: Re: Floating point libraries
Message-ID: <432@wuphys.UUCP>
Date: Mon, 20-Oct-86 12:13:56 EDT
Article-I.D.: wuphys.432
Posted: Mon Oct 20 12:13:56 1986
Date-Received: Tue, 21-Oct-86 23:57:45 EDT
References: <8610160630.AA06315@cory.Berkeley.EDU> <417@husc6.HARVARD.EDU>
Reply-To: lel@wuphys.UUCP (Lyle E. Levine)
Organization: Physics Dept., Washington U. in St. Louis
Lines: 82
Keywords: Fortran, Lattice, AmigaBasic
Summary: benchmarks

In article <417@husc6.HARVARD.EDU> hadeishi@husc4.UUCP (mitsuharu hadeishi) writes:
>In article <8610160630.AA06315@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes:
>
>	Actually the old Manx uses FFP only.  This makes Manx fast,
>but inaccurate.  Also FFP mathtrans.library doesn't support all of
>the transcendental functions that are available in most IEEE
>implementations; I'm not sure which functions aren't implemented.
>(FFP is only 32 bits, singel precision only.)
>
>	The next release of Manx will have options to use FFP, IEEE,
>68881 IEEE, and perhaps some others.
>
>	However, the new release of Lattice C contains a floating
>point library which is IEEE but is reputed to be about five times
>faster or more.  This makes it competitive with FFP, and also
>the data will be compatible with the 68881 (a VERY large plus for
>portability of floating point data between applications and machines.)
>Overall I would prefer to use the new Lattice fast IEEE libraries
>(highly optimized) over FFP since FFP is nonstandard (will not work
>with the 68881) and only works in single precision.
>
>				-Mitsu

I just got my new Absoft F77 compiler last week and have been
familiarizing myself with it and running benchmarks.  The first
tests I did were of the included IEEE floating point libraries.
The 1st tests compare Lettuce, AmigaBasic, and Fortran on just
multiplication loops.
          a=1
          loop i=1 to 100000
               a=a*1.0001
          end loop
Results: (from memory...)

            Lattice double:  ~120 sec
	    Lattice float:   ~180 sec
            Basic (double):  140 sec
	    Basic (float):   115 sec
	    Fortran float:   11.5 sec
	    Fortran double:  ~26  sec

The Fortran math library is IEEE compatible.
Lattice double is faster than Lattice single since it must pad and
truncate. What surprized me was the agonizing slowness of their
floating point calculations. Absoft, on the other hand, clearly
did a good job of optimizing their
floating point libraries. When I get time I'll
run some more benchmarks. If there is any interest, I'll post the
results. 

By the way, when is Lattice's new release due out? I haven't gotten
a card yet...  In the mean time, could someone run this benchmark
on a beta release for comparison:

	main()
	{
	int num;
	float/double a;
	a=1.;
	printf("%.0f\n",a);
	for (num=1;num<=100000;++num)
		a=a*1.0001;
	printf("%.0f\n",a);
	}

I just timed it with a stop watch.
 
			Thanks!


===============================================================================
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	Without computers, physics itself would be impossible.

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		   Lyle E. Levine

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