Computer Chess Club Archives




Subject: Re: PVS and MTD(f) branching factor

Author: Robert Hyatt

Date: 14:13:58 06/19/03

Go up one level in this thread

On June 18, 2003 at 12:56:36, Russell Reagan wrote:

>On June 18, 2003 at 04:24:00, martin fierz wrote:
>>better move ordering reduces the branching factor! you can easily see that from
>>best/worst case which is sqrt(N)(best) and N(worst) as branching factor for
>>alpha beta. that's not a constant speed improvement then...
>Hi Martin,
>Sorry if I wasn't very clear.
>I was wondering if pvs/mtd(f) with perfect move ordering led to a decrease in
>the branching factor over alpha-beta with perfect move ordering, or only a
>constant speedup. Better move ordering does lead to a reduced branching factor,
>but I was wondering about the situation where all 3 algorithms had perfect move
>ordering already.
>So, I am not talking about the improvement where you go from an N branching
>factor to a sqrt(N) branching factor, but when you go from alpha-beta with
>perfect move ordering, to pvs/mtd(f) with perfect move ordering.
>Does this make it more clear?

It can't.  You can't search less than the minimal alpha/beta tree, no matter
what you do, unless you use forward pruning...

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