Author: Christophe Theron
Date: 20:56:26 04/24/01
Go up one level in this thread
On April 24, 2001 at 20:38:49, Robert Hyatt wrote:
>On April 24, 2001 at 15:12:03, Christophe Theron wrote:
>
>>On April 24, 2001 at 10:13:29, Albert Silver wrote:
>>
>>>On April 24, 2001 at 10:01:04, Robert Hyatt wrote:
>>>
>>>>On April 24, 2001 at 05:06:40, Amir Ban wrote:
>>>>
>>>>>On April 24, 2001 at 03:47:15, Uri Blass wrote:
>>>>>
>>>>>>the best software that is not IBM.
>>>>>>
>>>>>>Suppose there is a match of 20 games at tournament time control
>>>>>>
>>>>>>I am interested to know how many people expect 20-0 for IBM
>>>>>>How many people expect 19.5-.5?....
>>>>>>
>>>>>>If IBM expect to do better result then the average result that the public expect
>>>>>>then they can earn something from playing a match of 20 games with Deep Blue.
>>>>>>
>>>>>>I believe that a part of the public who read the claim that kasparov played like
>>>>>>an IM are not going to expect good result for IBM.
>>>>>>
>>>>>>Uri
>>>>>
>>>>>I expect DB ('97 version) to lose 8-12.
>>>>>
>>>>>Amir
>>>>
>>>>
>>>>Based on what specific facts? How many games did they lose from their debut
>>>>in 1987 through 1995 the last event they played in with other computers? Let
>>>>me see.. that would be... _one_ game. So what suggests they would do worse
>>>>today? we are all 100x slower (or more).
>>>
>>>Yes, and another thing that is being seriously overlooked is just how important
>>>speed and a ply make in comp-comp matches. One thing that time and SSDF has
>>>CLEARLY taught is that that one ply in a comp-comp match makes a world of
>>>difference. I think pitting a PC program against DB would be a massacre, even if
>>>I don't think humans (a very top GM) would do that much worse against DB
>>>(compared to DB vs. PC) as opposed to an 8-way server run PC program as will be
>>>the case here. Provided the conditions were the same, and that both matches had
>>>equal preparation of course.
>>>
>>> Albert
>>
>>
>>
>>I'm not sure I would agree with you.
>>
>>Yes, Deep Blue is way faster than PC programs (even on today's PCs) in NPS, but
>>there is something you should not forget.
>>
>>Due to Hsu's beliefs, as pointed out by Bob several times, Deep Blue is
>>essentially a brute force searcher.
>>
>>But after 3 decades of chess programming on microcomputers we all know that
>>brute force search is extremely inefficient.
>>
>>Actually brute force is increasingly inefficient as ply depth increases. Or if
>>you prefer the difference between brute force and selective searches in terms of
>>nodes to compute to reach a given ply depth growth exponentially with ply depth.
>>
>>Today, good selective programs can achieve a "branching factor" which is under 3
>>(and that includes the extra work induced by extensions). A well designed brute
>>force alpha beta searcher, without extensions, achieves a BF between 4 and 5.
>>
>>Some time ago I have found that a good brute force alpha beta implementation has
>>a BF of 4.3.
>>
>>I think current top programs have a BF which is close to 2.5, but let's say it's
>>2.8 to keep some margin.
>>
>>
>>You can compute the ratio of nodes to search by brute force divide by nodes to
>>search by selective search by:
>>
>> ratio = 4.3^depth / 2.8^depth (^ mean "power")
>>
>>
>>Now about the NPS. Deep Blue is supposed to be able to compute 200 million NPS
>>(nodes per second). Current top PC programs on fastest hardware (single CPU) can
>>compute up to 800.000 NPS, that's 1/250 of what DB can do.
>>
>>
>>At what depth the "ratio" starts to be above 250?
>>
>>Answer: at ply depth 13.
>>
>>So I suspect that Deep Blue and current top programs on top hardware (single
>>CPU) can reach ply depth 13 in the same time.
>
>You _are_ aware that DB's branching factor was well below 5? I posted the
>analysis here a year ago (Ed probably still has it as he was interested). I
>took the 1997 logs and just computed the ratio using time. They were nowhere
>near 5... not even near 4...
I was not aware of that.
But given that Deep Blue reached ply depths higher than what I have written
above, I have good reasons to believe that their BF was indeed well below 4.
So they were using a selective algorithm.
I wonder what it was.
>>And it turns out that ply depth 13 can be routinely reached by today's PC
>>programs at standard time controls.
>
>Yes.. but don't forget DB was reaching depths of 15-18 in the middlegame,
>as their logs from 1997 clearly show...
Yes, it looks like I was badly informed.
Knowing that, I now believe that no micro program of today would have any
reasonnable chance against Deep Blue.
Against a single chip maybe, not against the whole thing.
>>But there are 2 things I'm not really taking into account here:
>>1) selective search is less reliable than brute force search
>>2) Deep Blue uses something called "Singular extensions" which increases its
>>branching factor dramatically over the BF of a simple alpha beta brute force
>>algorithm.
>>
>>
>>Point 1 is hard to evaluate.
>>
>>About point 2 we have some data suggesting that "singular extensions" is an
>>extremely expensive algorithm: while PC programs have no problem to reach ply
>>depth 13 on current hardware, Deep Blue could not go beyond ply depths 11-12 in
>>the 1997 match. Of course in some lines it was computing much deeper.
>
>Not again. Look at the logs. 11(6) is a +seventeen+ ply search.
>
>
>
>
>>
>>It remains to be seen if "Singular extensions" is such an improvement. So far I
>>think that nobody has managed to prove that it is. Some people speculate it
>>could be effective only if you have a very fast computer, but only the Deep Blue
>>experiment suggests this, without further scientific proof.
>
>No. I used them in later cray blitz versions. HiTech used them as well.
>They have their good and bad points. Some micro programs have/do use them
>as well...
I'm sorry but I still have to read a study about the success of this extension.
Anyway, if it is such a small improvement that it is not even clear by now clear
if it is good or not, then in my opinion the main (and maybe only) strength of
Deep Blue is its huge NPS.
But that's not new.
That's why I see Deep Blue as a technical and financial success, and just that,
certainly not as a breakthrough in computer chess.
Christophe
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