Author: Vasik Rajlich
Date: 09:49:00 10/19/04
Go up one level in this thread
On October 19, 2004 at 10:25:43, Anthony Cozzie wrote: >On October 19, 2004 at 08:24:45, Rick Bischoff wrote: > >>I am still struggling with my huge node count in WAC #Iforgotthenumber-- anyway, >>I am trying out lazy evaluation, e.g., only counting material and seeing if I >>can get a cutoff from there.. Here is the code in the evaluation function: >> >> //int x = whiteScore - blackScore; >> //extern bool wtm; >> //if ( !wtm ) x = -x; >> //if ( x + 200 <= alpha ) return alpha; >> //else if ( x - 200 >= beta ) return beta; >> >>When this code is off, as shown above, I have the following stats from a depth-7 >>search: >> >> 6 157 295 112333 1. Ne5 Qxb3 2. Nxd7+ Kc8 3. axb3 Kxd7 4. Rxa7 >> 7 153 1132 397249 1. Ne5 Qxb3 2. Nxd7+ Kc8 3. axb3 Kxd7 4. Rxa7 Nd5 >>1294061 nodes (1041179, 0.804583) 31.162 seconds (41526.9 NPS) >>4000 nullmove try 1330 nullmove succeed (%33.25) >> >>OK, so when I turn on the lazy evaulation: >> >> 6 53 403 198712 1. Ne5 Rf6 2. Bg5 Qxb3 3. axb3 Re6 >> 7 141 1720 752626 1. Ne5 Qxb3 2. axb3 Bxb5 3. Nxg6 Nxg6 4. Be3 >>move Ne5 >>3314059 nodes (2830629, 0.854128) 66.653 seconds (49721.1 NPS) >>171058 nullmove try 66872 nullmove succeed (%39.0932) >> >>So you can see, not only has the PV in the last two iterations changed >>drastically, the node count has also increased by a factor of 2 or more! >> >>Clearly, this has to be a bug? From the opening with lazy eval off: >> >> 6 0 50 24360 1. d4 d5 2. Bf4 Bf5 3. Nf3 Nc6 >> 7 10 263 107854 1. d4 d5 2. Bf4 Nc6 3. Nf3 Bf5 >>move d4 >>278745 nodes (225693, 0.809676) 6.184 seconds (45075.2 NPS) >>5307 nullmove try 2870 nullmove succeed (%54.0795) >> >>With it on: >> >> 6 0 48 24099 1. d4 d5 2. Bf4 Bf5 3. Nf3 Nc6 >> 7 10 257 110823 1. d4 d5 2. Bf4 Nc6 3. Nf3 Bf5 >>move d4 >>348815 nodes (289003, 0.828528) 6.985 seconds (49937.7 NPS) >>9995 nullmove try 3934 nullmove succeed (%39.3597) >> >>So, I am still getting a node increase here, but the PV has remained the same. >>What gives!? > >I am now going to give you the biggest secret in chess programming. If you want >the magic bullet for a good search, this is it. > >YOU HAVE NO IDEA WHAT THE HECK YOUR ENGINE IS DOING. > >You are getting a lot of nodes - but you have no idea why. Zappa has an option >to create a logfile (usually some GB in size) of every node. I have a specially >written GUI that can then view this and show every move it considered and what >the depths and alphas and betas and scores were. If you do this, you will be >_amazed_ at what stupidities you find. If you don't feel like writing a GUI, >you can write a logfile and grep through it, although if you are serious about >getting a strong program I think a GUI is worth it. > >For example > >$ grep 000000142234 > >000000142234 hash: s=30, T=FH, D=8 >000000142234 trying null [23,24] child=0000001422344 >000000142234 null returned 23 [1234 child nodes] >000000142234 Trying child Nf3 [20,24] d=8 cid=00000022232344 > >... > >You get the point. > >anthony You might also look into "Chant", by Andrei Fortuna - it's a variation visualizer. Vas
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