Author: Tom Kerrigan
Date: 15:57:09 05/30/00
Go up one level in this thread
On May 30, 2000 at 17:56:48, Robert Hyatt wrote: >On May 30, 2000 at 12:50:33, Tom Kerrigan wrote: > >>On May 30, 2000 at 10:45:41, Robert Hyatt wrote: >> >>>On May 30, 2000 at 01:34:27, Tom Kerrigan wrote: >>> >>>>On May 30, 2000 at 00:25:29, Robert Hyatt wrote: >>>> >>>>>On May 28, 2000 at 19:44:05, Tom Kerrigan wrote: >>>>> >>>>>>On May 28, 2000 at 10:02:05, Georg v. Zimmermann wrote: >>>>>> >>>>>>>Hi, >>>>>>> >>>>>>>today I realized that the program I'm toying around with does in its search() >>>>>>> >>>>>>>1.) generate all moves >>>>>>>2.) order the moves and put hash move if available to 1st position >>>>>>>3.) do the recursive search >>>>>>> >>>>>>>I thought that I could increase its speed by testing the hash move first and >>>>>>>only if not >= beta do the move generation and the rest. >>>>>>> >>>>>>>From my tests it shows that it sticks with the hash-move about 50% of the time. >>>>>>>Should this number be higher ? >>>>>>> >>>>>>>I was very dissapointed when I didn't notice any speedup after my changes. What >>>>>>>speedup should I expect ? Something like 0.5-1% or more like 1ply ? >>>>>> >>>>>>You can forget about 1 ply. Your program needs to go ~4x faster for it to search >>>>>>1 ply deeper. Which means that your move generator must be taking ~400% of the >>>>>>execution time, which is clearly impossible. >>>>> >>>>> >>>>> >>>>> >>>>>His effective branching factor might be different than yours. Mine is at about >>>>>3.0... I have seen some higher and some a bit lower. >>>> >>>>If you make a program 20% faster, it will not search 1 ply deeper, regardless of >>>>your branching factor. (Unless your branching factor is < 1, which doesn't seem >>>>likely.) >>>> >>>>> >>>>>> >>>>>>Here's what you have to consider when calculating your speedup: >>>>>> >>>>>>1) How many moves you get from the hash table. I just ran some random position >>>>>>and got a 1.75% "hit rate." >>>>> >>>>>That sounds horribly low. I'd be concerned of something serious if it drops >>>> >>>>I don't hash during quiescence and my hash table was pretty small when I ran >>>>that test. That may explain the low rate. But my point was that the expected >>>>speedup of the optimization should be small. Even if you have a hit rate of 50%, >>>>the speedup is still only 0.5 * 0.5 * 0.2 = 5%. >>>> >>>>-Tom >>> >>> >>>I don't hash in quiescence either. I haven't in many years. >>>However, I am not sure that your 5% number is right or wrong, buet 5% is >>>something I would definitely go for if I knew it was laying around. You get >>>enough of those, and you can get into big savings. I've found very few large >>>savings (25%) in Crafty over the years. But I have found many dozens of 1-3% >>>improvements, and an occasional 5-10% boost as well. >>> >>>I think the key to improving a program, once it plays legally, is to develop >>>a methodology to carefully profile the code, find the hot spots, and then find >>>ways to speed up those hot spots. But all the while paying _careful_ attention >>>to the overall node counts on a wide range of test positions. A 1% speedup is >>>of no use at all if you introduce an error that happens once every billion >>>nodes. I can search that many nodes in 15 minutes. I can't stand errors that >>>frequently. I have what would probably be called a "zero-tolerance for errors" >>>in Crafty. If I make a change that should only make it faster or slower, then >>>the node counts must remain constant. If they don't I debug until I find out why >>>and fix it. >> >>If you're not hashing during quiescence, how are you getting hit rates around >>40%? That's more than my percentage of non-quiescent nodes, period... >> >>-Tom > >I would assume that my q-search is not as big as yours, at present. I posted >the numbers I got on the BK test. You can eyeball my code to see how I do the >hashing. > >the bigger numbers come in simpler positions where there is almost no q-search >at all. All I'm saying is that the numbers you gave (e.g. 25%) are (hash hits/hash probes) and not (hash hits/nodes). The latter is what's more important in this case. -Tom
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