Author: Robert Hyatt
Date: 19:13:07 08/17/03
Go up one level in this thread
On August 17, 2003 at 04:39:43, Tony Werten wrote: >On August 16, 2003 at 23:14:45, Robert Hyatt wrote: > >>On August 16, 2003 at 07:23:49, Gian-Carlo Pascutto wrote: >> >>>On August 15, 2003 at 22:56:34, Robert Hyatt wrote: >>> >>>>On August 14, 2003 at 15:27:06, Peter Fendrich wrote: >>>> >>>>>1FH = The ratio where the first generated move in the node is a Fail High. >>>>> >>>>>I experimented with removing the the hash table and became a bit surprised. >>>>>Normally I have about 1FH = 95-96%. When I removed the hash table that figure >>>>>raised to more like 1FH = 96-97% while the search depth, as expected, was >>>>>decreased. >>>>> >>>>>Increased 1FH when removing the hash table. Is this normal? >>>> >>>>Probably. You increased the size of the tree. And for the extra stuff you >>>>searched, you searched it pretty accurately. But you _did_ search it, which >>>>slowed you down. :) >>> >>>No! - That does not make any sense at all. >> >>Sorry, but it makes _lots_ of sense. >> >>If you don't try a hash table move first, then you will probably try captures >>and captures have re-captures that work instantly. Hence more cutoffs. Just >>try it... >> >>The hash move is often _not_ a capture. But if you try a capture first, >>then the corresponding re-capture will be an instant cutoff that is easier >>to find than a reply to a non-capture. >> >>> >>>"the extra stuff you searched, you searched it pretty accurately" >>> >>>If we disabled hashing and hence handicap move ordering, we'll do >>>worse, not better, on average. >>> >>>Yes, we may generate extra nodes and do well there, but that's certainly >>>not what we should expected in the average case, since we just made >>>our move ordering worse! >>> >>>Do you see your contradiction? >> >>Not at all. See above. Which is easier to refute, a non-capture or a >>capture? >> >>Answer: A capture. > >This is incorrect. It will be the opposite most of the time. Place a queen on >the board, count the amount of bad captures it can make, now count the amount of >squares it can go to that are defended ( and the queen will be captured) > >I'm pretty sure the latter will be higher most of the time. > >Maybe you meant: Is a move easier refuted by a capture or a noncapture ? > >Tony I meant _both_. If you don't try the hash move, your first move is going to be a capture, most likely. And since it most likely wasn't the best move, the refutation will also be a capture which you will find quickly. That was my point. I won't claim it is true for all programs, but I debugged a situation like this a year or so back when I was changing the hash table, and I saw exactly the situation, where the fh's on the first move went up higher than usual... I suspect this is true (at least in my case) because I try winning and even captures first, if there is no suggested hash move. An even capture has an obvious reply. Your case is not very likely. IE with no hash move, I try captures first, before just sticking the queen on any possible square. And generally, the queen is _not_ the piece I see capturing very much, since I discount captures that appear to lose material, and most queen captures do exactly that... YMMV of course, depending on how you generate moves. > >> >>> >>>-- >>>GCP
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