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From: jimb@amd.UUCP (Jim Budler)
Newsgroups: net.micro.mac
Subject: Re: Harmonic Series Benchmark
Message-ID: <1363@amd.UUCP>
Date: Sun, 26-May-85 20:28:48 EDT
Article-I.D.: amd.1363
Posted: Sun May 26 20:28:48 1985
Date-Received: Mon, 27-May-85 00:43:58 EDT
References: <> <>
Reply-To: jimb@amd.UUCP (Jim Budler)
Organization: AMD MOSCAD
Lines: 61

In article <> jimb@amd.UUCP (Jim Budler) writes:
>In article <> jimb@amd.UUCP (Jim Budler) writes:
>>Someone on arpanet proposed a floating point benchmark of timing the
>>sum of the first 10,000 terms of the harmonic series, i.e. for 
>>i = 1 to 100000; sum = sum + 1/i;  
>>
>>He also stated the right answer was 9.787613 determined from a Vax 11/780
>>taking 0.02 seconds.
>>
>>Now either I'm doing it wrong or something
>
>Well, I now know the answer to my own question.

I went back and took another closer look at the problem.  The poster
of the problem specified 32 bits for the problem.  I redid my
program, using both floats(32 bit), doubles(64 bit), and extended (80
bit).  In addition I reread Bill Duval's words on the floating point
and eliminated the casts from the program.  
i.e. was:	j += ( 1.0 / (float) i ) where i is long.
     is:	j += ( 1.0 / i)

This resulted in a savings of about 5 seconds on the double, and
3 seconds on the float.

Here are my final results.  I'll post the source in net.sources.mac.
Actual output of the program.
-------------------------------------------------------------------
Calculating the sum of 10,000 terms of the harmonic series
Vax 11/780 with FPU took 0.02 seconds the answer was 9.787613
This result from originator of problem. Assumed "right" answer.

This is a Macintosh with Consulair Mac C 2.0,
using float, 32 bit precision:

Time = 29.43 Seconds	Sum = 9.787613

Using Doubles:
IBM3081 with UST System III took 0.00? seconds,
	the answer was 9.787606.
A Valid 68000 CAD workstation 4.1c BSD took 23 seconds,
	the answer was 9.787606.

This is a Macintosh with Consulair Mac C 2.0,
using double, 64 bit precision:

Time = 29.87 Seconds	Sum = 9.787606

Bill Duvall of Consulair recommends using extended,
80 bit precision for computation with Mac C as that is the
base mode of his implemntation of the SANE/IEEE numerics.

This is a Macintosh with Consulair Mac C 2.0,
using extended, 80 bit precision:

Time = 25.15 Seconds	Sum = 9.787606
-- 
 Jim Budler
 Advanced Micro Devices, Inc.
 (408) 749-5806
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