Author: Robert Hyatt

Date: 07:51:07 04/02/00

Go up one level in this thread

On April 01, 2000 at 22:49:09, leonid wrote: >On April 01, 2000 at 20:24:02, Robert Hyatt wrote: > >>On April 01, 2000 at 13:38:00, leonid wrote: >> >>>Hello! >>> >>>Maybe you could take me out of my endless confusion about "branching factor". >>>Confusion come from the way that you can compare two different games. Would like >>>your help in finding useful numbers about this factor. >>> >>>Reason for concern about "branching factor" is that it make me loose 10 times >>>speed when logic search 10 ply deep starting from ply 3. Calculation was done, >>>as precise as I could, comparing brute force search without any extensions for >>>two games. >>> >>>Branching factor for me (I know it is not the usual one but very practical one) >>>is division of number of nodes seeing in ply against total number of nodes for >>>given ply. If number of nodes seeing was 5 and number of nodes for this ply 32 >>>-"branching factor" is around 16%. >>> >>>Confusion is that when I found my branching factor for the entire game it was >>>around 7%. When I see the branching factor for the ply over two lowest it is as >>>high as 21%. In good games I could see branching factor only starting from ply 6 >>>and it is around 15%. I have no idea what is the branching factor in other games >>>calculated for entire game. >>> >>>Please indicate me branching factor for entire game and for the ply over 6 if >>>you can. It could help me. Please say me this factor only for the brute force >>>search. In quick logic my branching factor is different and much smaller. >>> >>>Thanks for your help, >>>Leonid. >> >> >>the 'branching factor' number is generally used wrongly. It is roughly 38 in >>the game of chess, averaged over the complete game. "effective branching >>factor" is the number you are really looking for. Best way to calculate that >>is to do a search, then compute the following: >> >>for each iteration, compute exactly how much time it took. IE suppose you >>get the following times: > > >Do the "iteration" signify simply number of ply? And do you say "get the >following times" in the sense of time to solve the position for given ply in >(maybe) seconds ? > > >>iteration time >> >> 1 0 >> 2 3 >> 3 9 >> 4 24 >> >>you compute three values: >> >>t1=3-0 = 3; >>t2=9-3 = 6; >>t3=24-9=15; >> >>you can compute two estimates of your effective branching factor: >> >>b1=6/3 >>b2=15/6 >> >>those are the interesting numbers. IE if you know the time to do a depth=n >>search, what do you multiply that by to compute how long it will take to do >>depth N+1? > >I have the impression that your way to calculate is different from mine. If the >word "iteration" I undertood really as it must be. > >My biggest problem, in all my calculation, was the fact that I can see the time >that it took in other games starting from ply 6, on mine AMD 400Mhz. This way I >have no access to find the speed for the lowest two plies. And it is those >lowest two plies that do the most of the work. They can dramatically change the >speed of the entire game. I know, for instance, that you also have written your >lowest ply in different way and probably many other did. > >With my respect! >Leonid. what you want is the total time to complete iteration N divided by the total time to complete iteration N-1. Or the total nodes for each, which ought to be roughly equivalent.

- Re: Branching factor, make me confuse more that ever.
**leonid***12:21:46 04/02/00*

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