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From: philip@pescadero.Stanford.EDU (Philip Machanick)
Newsgroups: comp.sys.next
Subject: Re: NeXTStation Benchmark
Message-ID: <1990Nov16.192938.17923@Neon.Stanford.EDU>
Date: 16 Nov 90 19:29:38 GMT
References: <743@kaos.MATH.UCLA.EDU>
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Organization: Computer Science Department, Stanford University
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In article <743@kaos.MATH.UCLA.EDU>, barry@pico.math.ucla.edu (Barry Merriman) writes:
|> Add this to the list (thanks Eric Anderson):
|> 
|> DECStation 3100 (using gcc -O)
|> 
|>   4.0 MFLOPS (vs about 1.3 MFLOPS using just ``cc -O'')
|> So, the DECStation takes the lead (in performance, but not price/performance).
|> But---what can you say about a company whose default compiler
|> is worse than a freely available one? :-)

Now, wait a minute. In your original article, you reported the DECstation as
> DecStation 3100:
>         0.5u 0.0s 0:00 100% 41+31k 0+0io 0pf+0w 
>         => 2.0 MFLOPS
Still, a factor of 2 difference looks suspicious. I decided to check this
out myself. My results looked like this on the DECstation 3100:
cc -O:
0.6u 0.0s 0:00 82% 30+30k 3+0io 0pf+0w
gcc -O:
0.2u 0.0s 0:00 86% 30+31k 0+0io 0pf+0w
Even worse - now gcc is 3 times faster. When I get bizarre results, I
check them - so I looked at the output of the program. The result of
  x=1.0000; 
  m=1.00001;
  for (i=1;i<1000000;i++) {x *= m;}
is 1.00001 to the power 1000000, which my calculators claim is 22025.365.
Output from cc:
  x = 22323.087891 (1% different from calculators)
Output from gcc:
  x = 0.000000 (seriously bogus)
So - how about another round of runs, this time checking the output?
Not that I'd advocate wasting too much time on this - toy benchmarks don't
tell you much anyway.
-- 
Philip Machanick
philip@pescadero.stanford.edu