From: Jerry Donald Watson Date: Sun, 12 Aug 2018 07:47:30 +0000 (+0200) Subject: Simple razoring: depth 1 only, no distinction between PV / NonPV X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=348cd5ed74e808733545c392d1bd80965a379617;ds=sidebyside Simple razoring: depth 1 only, no distinction between PV / NonPV We simplify the razoring logic by applying it to all nodes at depth 1 only. An added advantage is that only one razor margin is needed now, and we treat PV and Non-PV nodes in the same manner. How to continue? - There may be some conditions in which depth 2 razoring is beneficial. - We can see whether the razor margin can be tuned, perhaps even with a different value for PV nodes. - Perhaps we can unify the treatment of PV and Non-PV nodes in other parts of the search as well. STC: LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 5474 W: 1281 L: 1127 D: 3066 http://tests.stockfishchess.org/tests/view/5b6de3b20ebc5902bdba0d1e LTC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 62670 W: 10749 L: 10697 D: 41224 http://tests.stockfishchess.org/tests/view/5b6dee340ebc5902bdba0eb0 In addition, we ran a fixed LTC test against a similar patch which also passed SPRT [-3, 1]: ELO: 0.23 +-2.1 (95%) LOS: 58.6% Total: 36412 W: 6168 L: 6144 D: 24100 http://tests.stockfishchess.org/tests/view/5b6e83940ebc5902bdba1485 We are opting for this patch as the more logical and simple of the two, and it appears to be no less strong. Thanks in particular to @DU-jdto for input into this patch. Bench: 4476945 --- diff --git a/src/search.cpp b/src/search.cpp index 8f7d263a..bd5eb260 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -66,7 +66,7 @@ namespace { constexpr int SkipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 }; // Razor and futility margins - constexpr int RazorMargin[] = {0, 590, 604}; + constexpr int RazorMargin = 600; Value futility_margin(Depth d, bool improving) { return Value((175 - 50 * improving) * d / ONE_PLY); } @@ -730,15 +730,9 @@ namespace { } // Step 7. Razoring (~2 Elo) - if ( !PvNode - && depth < 3 * ONE_PLY - && eval <= alpha - RazorMargin[depth / ONE_PLY]) - { - Value ralpha = alpha - (depth >= 2 * ONE_PLY) * RazorMargin[depth / ONE_PLY]; - Value v = qsearch(pos, ss, ralpha, ralpha+1); - if (depth < 2 * ONE_PLY || v <= ralpha) - return v; - } + if ( depth < 2 * ONE_PLY + && eval <= alpha - RazorMargin) + return qsearch(pos, ss, alpha, beta); improving = ss->staticEval >= (ss-2)->staticEval || (ss-2)->staticEval == VALUE_NONE;