Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: New crap statement ? Perpetuum mobile

Author: Miguel A. Ballicora

Date: 07:56:25 09/30/01

Go up one level in this thread


On September 29, 2001 at 14:54:03, Robert Hyatt wrote:

>On September 29, 2001 at 10:41:37, Miguel A. Ballicora wrote:
>
>>On September 29, 2001 at 10:01:11, Robert Hyatt wrote:
>>
>>>On September 28, 2001 at 00:00:43, Miguel A. Ballicora wrote:
>>>
>>>>On September 27, 2001 at 18:06:34, Olaf Jenkner wrote:
>>>>
>>>>>>If you can consistently produce a speedup of 3.0, then I can time-
>>>>>>slice that same algorithm on one cpu and get a speedup of 1.5.  And I can do it
>>>>>>for _any_ alpha/beta algorithm you do in parallel.  Every time. And using your
>>>>>>code, it will be easy for me to do it.
>>>>>>
>>>>>It's a good explanation. Some people seem to believe to perpetuum mobiles.
>>>>
>>>>Some believe that objects heavier than air will never fly.
>>>>Everybody knows, that's against physics.
>>>>
>>>>Regards,
>>>>Miguel
>>>
>>>
>>>I think you worded that wrong.  Airplanes are heavier than air and have been
>>>flying for 100 years now.  I think you meant the bumble-bee, because no one
>>>believed they could move their wings rapidly enough to produce the lift required
>>>to get them off the ground.
>>
>>I worded right, I was sarcastic to answer a sarcastic message.
>>
>>>There is a difference between "believed to be impossible" and "known to be
>>>impossible."
>>
>>Exactly my point.
>>
>>>super-linear speedups are provably impossible.  I've already given the simple
>>>proof.
>>
>>Then, I missed it. If you refer to doing two threads "slicing the time" this
>>requires an overhead, and that means that using two processors are > 2.0 or
>><2.0, who knows. (it could be 2.0001, or more, we do not know how future cpus
>>will behave). Still, that was not the interesting part of the discussion. The
>>interesting part was if an algorithm with two threads could be better than one.
>>
>
>It requires no overhead to mention.  Every N milliseconds the processor handle
>a timer interrupt.  I choose that point to switch to the other thread.  The
>cost is minimal.
>
>You overlook the fact that the parallel search _also_ has its own kind of
>overhead problems...  that would be eliminated in the approach needed for
>a serial version (ie no atomic locks that are very slow...  etc.)

I do not overlook that. That is true in the current generation of processors.
You cannot guarantee the same in the future. You are trying to prove something
with experimental observation. I would agree if you say that in the
current "context".

>>Super-linear speedups are "probably" impossible but so far I did not see that
>>they are "provably" impossible. I would settle with "They are believed to be
>>impossible".
>>
>>Regards,
>>Miguel

>They simply _are_ impossible.  Unless you believe in perpetual
>motion, infinite compression, a fire that will burn forever, etc.

What I believe is irrelevant. In fact, I do not believe it is possible to
have super-linear speedups, but I have not seen it proved.
Comparison with physic laws do not bear any demostration more that a
sarcastic effect, which still does not prove anything. Besides, at one point
you mention the law of mass conservancy. That showed to be an universal truth
until Einstein's generation. Lavoisier and Newton are still right under their
own context. If we continue to come up with physic's analogies we will end up
discussing something totally irrelevant to the analysis of an algorithm.

Regards,
Miguel





This page took 0 seconds to execute

Last modified: Thu, 15 Apr 21 08:11:13 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.