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From: root@cca.ucsf.edu (Systems Staff)
Newsgroups: comp.os.minix
Subject: Re: Dhrystone 2.1 sample run
Summary: Proposed Drhystone 2.1 changes
Message-ID: <2499@ucsfcca.ucsf.edu>
Date: 14 Oct 89 01:46:53 GMT
References: <24988@louie.udel.EDU> <2457@ucsfcca.ucsf.edu> <3545@ast.cs.vu.nl> <1377@majestix.ida.liu.se>
Organization: Computer Center, UCSF
Lines: 61

In article <1377@majestix.ida.liu.se>, mwe@majestix.ida.liu.se (Mikael Wedlin) writes:
> In article <2482@ucsfcca.ucsf.edu> root@cca.ucsf.edu (Systems Staff) writes:
> >> 
> >> However, I consider it extremely poor human engineering to print out
> >> a ton of lines that are the same (pairwise), apparently with the
> >> idea that the user is to compare them.  Why can't the computer do that?

For the computer to do that would require writing the data produced to
a file then processing the file to determine its correctness. Remember
compiler analysis of the program must not be able to decide that any of
its timed computations are redundant.

Now we would have portability problems (Dhrystone is not just for Unix
systems) so there would be twiddling to define the file to be used etc.

Then we would have to read the file back in to check it (complicating
the program and raising I/O compatibility issues). It wouldn't avoid
these problems to create a separate program to do the checking and
we can't depend on the presence of such utilities as "diff" which
is absent from many systems.

> >Under no circumstances make such deletions!
> >
> How about 'noice = fopen("/dev/null", "w");' ?
> 	/Mikael

A change that keeps it neat is to change the printf('s that produce
the desired results to fprintf(stderr,'s then you can redirect stdout
to /dev/null (on systems that support this) _after_you_have_verified_
the_test_output_. Doing it this way rather than the other way around
is again for portability to shells that don't allow independent
redirection of stderr.

And, of course, you can just follow my previous suggestion and select
the output with tail, e.g.

     echo 10000 | dry2 | tail -3

without changing the program at all. The obvious one line script

    echo $1 | dry2 | tail -3

makes it straightforward to use. But you must still check the
verification output the first time after recompiling.

The other problem is that Dhrystone 2.1 uses floating point to 
compute its results. I think this should be changed and am pursuing
the point.


 Thos Sumner       Internet: thos@cca.ucsf.edu
 (The I.G.)        UUCP: ...ucbvax!ucsfcgl!cca.ucsf!thos
                   BITNET:  thos@ucsfcca

 U.S. Mail:  Thos Sumner, Computer Center, Rm U-76, UCSF
             San Francisco, CA 94143-0704 USA

I hear nothing in life is certain but death and taxes -- and they're
working on death.

#include <disclaimer.std>