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Subject: Re: More on the "bad math" after an important email...Appeal to you both

Author: Robert Hyatt

Date: 07:25:38 09/04/02

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On September 04, 2002 at 02:47:20, Uri Blass wrote:

>
>I here agree with GCP
>If Vincent's target was to convince the sponsor
>not to look at the speedup of crayblitz as real he probably
>suceeded.
>
>He does not need to prove that the results of the
>speed up are a lie but only to convince them
>not to trust the results.
>
>The times and not the speedup are the important information.
>
>Times are calculated first and speedup is calculated only
>later after knowing the times.

I've said it several times, but once more won't hurt, I guess.

The original speedup numbers came _directly_ from the log files.  Which
had _real_ times in them.  The nodes and times were added _way_ later.
Once you have a speedup for 2,4,8 and 16 processors, you can _clearly_
(and _correctly_) reconstruct either the time, or the nodes searched,
or both.  We _had_ to calculate the nodes searched for reasons already given.
It is possible that the times were calculated in the same way.  I didn't do
that personally, and without the "log eater" I can't confirm whether it was
done or not.

If you don't trust the speedups, that's something you have to decide, and it
really doesn't matter to me since that program is no longer playing anyway.  In
fact, I don't have any source code for the thing as that was one of the many
things lost when I lost the logs and everything else.

But, as I said, the paper was about the _performance_.  And the speedup
numbers were direct computations from raw data.  I consider _that_ to be
the important data presented in the paper, along with the description of how
the algorithm worked.



>
>Usually we tend to trust scientists but if the information
>about times is wrong then it means that
>we cannot trust the other details in the article.



So if the _main_ data is correct, and is then used to calculate something
else, the something-else can't be trusted, and therefore neither can the
main data???

Perhaps I am missing something...




>
>Uri



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