Author: Stuart Cracraft
Date: 08:55:58 09/05/04
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On September 03, 2004 at 10:47:38, Tord Romstad wrote: >On September 03, 2004 at 10:14:53, Stuart Cracraft wrote: > >>On September 03, 2004 at 09:47:26, Jan K. wrote: >> >>>You should look for bugs in your search....i find the move even with no >>>extensions but the threat extension set to 1/2 ply and no checks in qsearch. >>>Takes 60 seconds and almost the same number of nodes like your full search. >> >>Tord said something about having the null move search a window >>wider than -beta+1,beta and and then testing the return value >>against alpha-MARGIN. If less than that, a faillow and then >>extending. > >This was in the context of BM extensions, not mate threat extensions. For >mate threat extensions, there is no reason to use a wide window for the >null move search. The only thing you need to remember is that if you >use a fail-hard search, you must remember to return exact scores instead >of bounds if the exact score is a mate. I changed my program to do this for all values, not only mates. It was doing that for mates before. I changed each return of a bound to a value return and tested after each and nothing changed except the speed of the search and tree-size. The suite result was the same. Interesting. > >>Has anyone else with PVS search implemented mate. Can you just >>include your code fragment in reply to this. I have programmer's >>block. > >Sure. Here is the null move part of the code in my new engine (which >uses PVS), with some irrelevant noise removed in order to make it easier >to read. The BM extension is not yet implemented. > > if(nullmove && Ply>0 && !ss->check && !mate_threat && ss->eval >= beta && > ss->material[WHITE]>0 && ss->material[BLACK]>0) { > > make_nullmove(); > nullvalue = -search(-beta, -beta+1, depth-4*PLY, 0, 0); > unmake_nullmove(); > > if(nullvalue >= beta) return nullvalue; > if(nullvalue <= -MATE_VALUE+Ply+2) mate_threat = 1; > } > >Tord Do you increment ply within search? For me, ply is a parameter to search and I have experimented both with and without incrementing it with if nullvalue == -MATE+ply+2, but no substantive improvement for the result on test suite. Just parity. Same score. Note, when I change from == to <=, my search blows up and crashes on the first position. Stuart
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