Author: Vincent Diepeveen
Date: 06:02:48 04/25/01
Go up one level in this thread
On April 24, 2001 at 23:56:26, Christophe Theron wrote:
>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.
without hashtable, fullwidth, hardware timing, parallel problems,
huge qsearch, singular extensions.
WITH nullmove and WITH hashtable and WITH SE and recaptures i never
get even to 15 ply...
>So they were using a selective algorithm.
>I wonder what it was.
No they weren't using a selective algorithm.
Hsu even writes in IEEE99 uses a typical 12 ply search as example.
The only thing which is not clear is how many plies he did in
hardware.
If they were selective like now is said then that would mean
that deep blue was the tactical worst program ever build as for
a simple tactical trick they needed 8 ply to find it:
---------------------------------------
--> 16. Qd3 <-- 24/91:38
---------------------------------------
hash guess Nd5c7,Guessing Nc7
6(4)[b3](29)[Qc3](30) 30^ T=1
qd3c3 Qe7d8 bg6f7 Pa7a5 bg3c7N Qd8c7b qc3c7Q Kc8c7q bf7e6P Bb7f3n
6(5)[Qc3](61) 61^ T=1
qd3c3 Qe7d8 bg6f7 Pa7a5 bg3c7N Qd8c7b qc3c7Q Kc8c7q bf7e6P Bb7f3n
6(5)[Qc3](16)[c3](32)[c4](46) 46 T=5
pc2c4 Qe7b4 pb2b3 Bf8d6 bg3d6B Qb4d6b ra1a7P
7(5) #[c4](23)####################################################[Ra3](41)# 41
T=10
ra1a3 Bb7d5 bg3c7N Kc8c7b qd3b5P Nd7b6 re1a1 Qe7b4
8(6) #[Ra3](11) 11v T=14
ra1a3 Bb7d5 bg3c7N Kc8c7b qd3b5P Nd7b6 re1a1 Pa7a5 qb5d5B Pe6d5q
8(6) #[Ra3](26)##################################################### 26 T=58
ra1a3 Bb7d5 re1a1 Bd5c4 qd3d2 Kc8b7 bg3c7N Kb7c7b ra3a7P
9(6) #[Ra3](35)#<ch> 'Bc6'
---------------------------------------
--> Bb7c6 <--
---------------------------------------
35 T=172
ra1a3 Bb7d5 bg3c7N Kc8c7b qd3b5P Nd7b6 re1a1 Pa7a5 ra3a5P Ra8a5r ra1a5R Qe7b4
this is from hashtable. It is the pv of the 10th ply there.
Every move which has a N or b or whatever behind it means it's a capture
so extended.
3(4) 30^ T=0
bg6f5 Qe7b4
Does the above look like a 7 ply search to you?
No it looks like a 3 ply search to me
3(5) 48 T=0
bg6f5 Qe7b4
Does the above look like a 8 ply search to you?
It is the same pv. It's even the same depth. Hardware processors
just do 1 ply extra.
4(5) 48 T=0
bg6f5 Qe7b4
Now they get to a 4 ply search.
5(5)[Bf5](18) 18v T=0
bg6f5 Qe7b4 re1e6P
Only now we see more plies. The bigger search depth allows
more extensions behind pv. it gets more serious now.
We all know the publications from the deep blue team on extensions how
they limited them. it's limited depending upon search depth. Each ply
they allow at most 2 extensions. I do not have this limit in diep
as i control my extensions better!
5(5)[Bf5](54)[c4](78) 78^ T=0
pc2c4 Nd5b4
5(5)[c4](97) 97 T=1
pc2c4 Nd5b4
6(5)[c4](87) 87 T=2
pc2c4 Nd5b4 qd3c3
Is the above line a 11 ply PV? No way. Not even 6 ply. It's just 3 ply!
One move deep blue always seems to get for free somehow in its pv.
Note that c4 attacks a piece and that Nb4 moves that piece away.
Simplistic case of a threat extension. Qc3 again attacks the piece
and gets away from the attack. So we again see here 1 normal move and
2 extensions. Very easy to extend all that. The search depth allows
the extensions as the depth to which things are allowed to get extended
has to do with the search depth.
Why do the hardware processors remain at (5) here all the time?
Because only now they get one ply extra!
7(5) #[c4](87)##################################################### 87 T=3
pc2c4 Nd5b4 qd3e2 Pb5c4p qe2c4P Nd7b6
See all the captures, that's all too simplistic to call this a 12 ply
search. This realy is a 2 ply search with loads of extensions.
As all processors need like 0.5 seconds timeout for just a few nodes a few
hardware processors already need 3 seconds.
8(6) #[c4](57) 57v T=8
pc2c4 Nd5b4 qd3e2 Pb5c4p qe2c4P Nd7b6 qc4c6B Nb4c6q ra1a7P Nc6a7r
8(6) #[c4](56)#[Bf5](117) 117^ T=16
bg6f5 Kc8b7 re1e6P Qe7b4 re6c6B Kb7c6r bf5d7N Kc6d7b nf3e5 Kd7e6 ne5g6 Qb4b2p
qd3e4
So finally at 8 ply Bf5 is found. Good lord. If this is 14 ply then
deep blue is the tactical worst program ever!
Even a program that doesn't use a single extension finds this tactical
win sooner as 14 ply. Not to mention a hardware processor which does
loads of things in qsearch and even extends extra ply if needed.
How to ever explain that this is a 14 ply search to find a tactical
trick which i find if i turn on recaptures also at 8 ply.
note shredder4 even in preprocessor version which hardly has
king safety found it at 8 ply with recaptures. Shredder4 is
forward pruning like hell but still finds this as it has recaptures.
Yes it finds it because this is a tactical shot, NOT a positional shot...
If it needs a 14 ply search to find this tactical shot
then Deep Blue was the biggest joke program ever made!
The long search line you see are all extensions which automatically get
triggered in PV, as detecting SE moves in PVs is easier and all captures
it seems to extend anyway.
8(6) #[Bf5](148) 148^ T=18
bg6f5 Kc8b7 re1e6P Qe7b4 re6c6B Kb7c6r bf5d7N Kc6d7b qd3f5 Kd7c6 qf5e6 Kc6b7
qe6d5N
5 of the plies are captures. Leaves 8 ply. 2 moves are a check and
we can go on like that.
Not a single normal move here.
See however at 6[5] where 3 more or less normal plies are shown.
That's not a 11 ply search...
8(6) #[Bf5](137)##################################################### 137 T=37
bg6f5 Pe6f5b re1e7Q Bf8e7r pc2c4 Pb5c4p qd3c4P Nd5b4 ra1a4 Kc8b7
9(6) #[Bf5](137)#[TIMEOUT] 137 T=184
bg6f5 Pe6f5b re1e7Q Nd5e7r qd3c3 Pa7a5 ra1a5P Ra8a5r qc3a5R Ne7d5 qa5a6 Bc6b7
qa6e6 Kc8d8 qe6f5P
---------------------------------------
--> 17. Bf5 <-- 23/88:25
---------------------------------------
>
>>>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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