Author: chandler yergin
Date: 18:53:24 10/11/05
Go up one level in this thread
On October 11, 2005 at 21:34:44, Dann Corbit wrote: >On October 11, 2005 at 21:10:59, chandler yergin wrote: > >>On October 11, 2005 at 20:58:29, Dann Corbit wrote: >> >>>On October 11, 2005 at 20:47:54, chandler yergin wrote: >>> >>>>On October 11, 2005 at 20:34:28, Michael Yee wrote: >>>> >>>>>On October 11, 2005 at 19:52:46, chandler yergin wrote: >>>>> >>>>>>On October 11, 2005 at 19:43:59, Michael Yee wrote: >>>>>> >>>>>>>On October 11, 2005 at 17:46:02, chandler yergin wrote: >>>>>>> >>>>>>>>I apologize if I have offended anyone. >>>>>>>>A case of "Apples & Oranges" again.. >>>>>>>>Misunderstandings.. >>>>>>>>Stephen, and a few others here, know I seldom voice "Opinions"; >>>>>>>>I Post facts.. >>>>>>>>That way... if someone differs from the Post, they should attack the Fact, >>>>>>>>not the Poster. >>>>>>>>It doesn't always work that way... >>>>>>>>Everything I have Posted about Computer Chess Programs..I gave the Link >>>>>>>>Everything else I have Posted about Engines, Analysis Modules, is directly >>>>>>>>from the Chessbase Manual. It therefore refers to the Top Commercial >>>>>>>>Programs only.. Fritz, & Shredder >>>>>>>>Many of you that Program your own Engines 'tweak' them as you desire, >>>>>>>>and have a lot of fun. >>>>>>>>Players mostly use the Top Commercial Programs to assist in their play >>>>>>>>and improve their expertise. >>>>>>>>Thanks to a recent Post by Dan H. some of the confusion has been cleared up. >>>>>>>>Chessbase does use Mini/Max and so does indeed search every legal move >>>>>>>>for every position. >>>>>>>>So the "Apples & Oranges" now are just the difference between the Top >>>>>>>>Commercial Programs and the others. >>>>>>>>I find it very intersting that some of the 'lesser' Engines are really >>>>>>>>kicking Butt! Congrats to all! Keep it up... >>>>>>>>A Swift Kick only hurts for a little while.. >>>>>>>>;) >>>>>>>>Chan >>>>>>> >>>>>>> >>>>>>>The posts from Dan don't say that chessbase uses minimax and searches every >>>>>>>legal move for every position. >>>>>> >>>>>>I know he didn't say it.. I said it! >>>>>> >>>>>> In fact, he said something almost the >>>>>>>opposite--that if a program worked that way, it would be crushed. >>>>>> >>>>>>Just plain wrong..sorry. >>>>>>> >>>>>>>You actually supplied evidence of the answer in one of your other posts (where >>>>>>>you provide a description of the analysis output). The analysis window reported: >>>>>>> >>>>>>>search depth = 12 (selective depth 40) >>>>>>>positions searched = 4.2 x 10^7 >>>>>> >>>>>>I was using an example.. the type of info the Analysis Module window shows. >>>>>> >>>>>>> >>>>>>>If the analysis module really searched every position up to depth 12 >>>>>>>(approximately 20 moves, 20 replies to each of those moves, 20 replies to each >>>>>>>of those replies, etc.), then it would have searched >>>>>>> >>>>>>>20^12 = 4.1 x 10^15 positions >>>>>>> >>>>>>>This is way more than what was reported in the analysis window. (And the 20 is a >>>>>>>very low estimate of average moves per position anyway.) Instead, >>>>>>> >>>>>>>4.32^12 = 4.22 x 10^7 >>>>>>> >>>>>>>shows a branching factor that's more like 4--i.e., the program was not searching >>>>>>>every move in every position. >>>>>>> >>>>>>>Michael >>>>>> Michael, Please read the Chessbase Manual! >>>>>>Do you have Chessbase? Do you have Fritz or Shredder? >>>>>>If so Start the engine look at the Analysis Window as I have requested. >>>>>>You will find what I said. EVERY Legal move in the position is evaluated. >>>>>>It's the way it works. Like it or not. >>>>> >>>>>Some commercial engines I have include an old fritz 7, shredder 9 uci, fruit >>>>>2.2, and gandalf 6. I've analyzed positions before (e.g., during some of the >>>>>recent World Championship games from Argentina). What I see are depths, >>>>>selective depths, and node counts that are not consistent with a program that >>>>>searches every legal move in every position. >>>>> >>>>>You're right that engines do look at each move in the root (initial) position >>>>>(as Dann noted in another post). If that's what you meant, then I agree. But you >>>>>seem to referring to *all* positions (not just the root). >>>> >>>>No Michael, and as Shakespeare said.. "Aye, there lies the rub.." >>>>Please re-read my Post carefully. >>>>Well.. here.. >>>>"Start your Engine for a position or at any part of a game. >>>>Look at the analysis window >>>>What do you see? >>>>The analysis module should show the following: >>>>The name of the Engine >>>>The search depth (brute force selective) Example "12/40" means that all >>>>variations were >>>>searched to a depth of 12 ply, while some promising continuations were checked >>>>down to 40 ply. >>>>Next should show the move currently being investigated. Example f4-d6 (3/47) >>>>meaning number 3 of 47 legal moves in the position. >>>>Next it will show the speed at which the program is running. >>>>Example: 403kN/s means it is looking at 403,000 nodes (= positions) per second. >>>>This is normal on a 400MHz processor. >>>>The main variation for example shows "=(0.00)", then the best sequence of moves >>>>the program has found so far, the amount of time it has spent computing on the >>>>position,(1 min. 46 sec) and the number of positions it has examined >>>>(41937kN =41,973,000) >>>>The evaluation expressed in units of a pawn, always from the point of view of >>>>White >>>>"+0.53) means the program thinks White has an advantage of about half a pawn; >>>>" (-3.52" indicates Black is more than a piece up. If Mate is found the Program >>>>stops calculating and displays the Mate. (Mate in 6)." >>>> >>>>What if anything is incorrect in the above? >>> >>>There is nothing wrong in the statements above. The problem is in your failure >>>to understand what they mean. >> >>If I didn't understand it, I wouldn't have posted it. >>To have a meaningful dialog about anything, both parties should have the >>same consensus about the meaning. >>I Posted my meaning; was looking for constructive comments by those that had a >>different view. I sure got them.. but instead of commenting on specifics, >>they were just personal attacks, with nothing constructive, >>I appreciate your review! Please add where you believe I err. >>Thanks and sincere Best Wishes, >>Chan > >You err in thinking that chess programs use mini/max to search. Chessbase does! Ask them. > They use a more You say 'they' without being specific. >sophisticated variant called alpha/beta which cuts the branching factor from 20 >to around 6. Then they trim that further with lots of speculation that >typically results in a branching factor of under 3. Notice that this does not >mean that it seaches half as many nodes, but that in a 17 ply search it is >searching less than one trillionth as many nodes as it would with a full width >search. > >You err in thinking that a ply is the same as fullmove. A ply is 1/2 of a full >move and constitues one turn for a player of a given color. You err.. as many have before. My Quote: "Yes I understand the common terminology of Ply. That's why I was careful & precise to note that "for analysis purposes" Chessbase considers 1 ply(= half moves, i.e. one move for each side) and evaluates every legal move in a position 1/2 ply at a time, which is 1 iteration." > >You err in thinking that professional chess programs examine every node during a >search. No I don't They search a microscopic fraction of the total number of nodes. Of course! Take >a bathtub full of water. Now take an eyedropper and get some of the water. >Squeeze gently to eek out the smallest drop you can create. On a 17 ply search >the ratio between nodes examined and nodes ignored is less than the ratio of >water in the bathtub to that drop you just made. > >>>>>You yourself computed a while ago an estimate of the number of move sequences >>>>>that can happen from the start position. Given the nodes per second you see in >>>>>the analysis windows, how could the engine possibly be following all move >>>>>sequences (even taking into account transpositions)? I did not compute anything, I was quoting from an example given in the Manual. It was an Example they used to illustrate. >>>> >>>>That was Dann, not me.. >>>>> >>>>>Michael
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