Tweak reductions formula: 0.88 * depth + 0.12

locutus2 · snicolet · commit 50287a55d3b0 · 2018-07-23T09:16:29.000+02:00
Replace the depth part in the reduction formula for higher depths with a slower growing linear function. So for depth > 3 less reductions are used. What we can try next: - move the break point to even higher depths - tweak the slope for lower and higher depth - even possibly use a further higher depth threshold for a another slower growing function STC: LLR: 2.95 (-2.94,2.94) [0.00,5.00] Total: 25317 W: 5763 L: 5505 D: 14049 http://tests.stockfishchess.org/tests/view/5b54f9f70ebc5902bdb840ed LTC: LLR: 2.96 (-2.94,2.94) [0.00,5.00] Total: 7451 W: 1320 L: 1167 D: 4964 http://tests.stockfishchess.org/tests/view/5b54feeb0ebc5902bdb84244 Closes #1692 Bench: 4617359
diff --git a/src/search.cpp b/src/search.cpp
@@ -153,7 +153,8 @@ void Search::init() {
       for (int d = 1; d < 64; ++d)
           for (int mc = 1; mc < 64; ++mc)
           {
-              double r = log(d) * log(mc) / 1.95;
+              double slope = d > 2 ? 0.88 * d + 0.36 : d;
+              double r = log(slope) * log(mc) / 1.95;
 
               Reductions[NonPV][imp][d][mc] = int(std::round(r));
               Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);

Original file line number	Diff line number	Diff line change
`@@ -153,7 +153,8 @@ void Search::init() {`
`153`	`153`	`for (int d = 1; d < 64; ++d)`
`154`	`154`	`for (int mc = 1; mc < 64; ++mc)`
`155`	`155`	`{`
`156`		`- double r = log(d) * log(mc) / 1.95;`
	`156`	`+ double slope = d > 2 ? 0.88 * d + 0.36 : d;`
	`157`	`+ double r = log(slope) * log(mc) / 1.95;`
`157`	`158`
`158`	`159`	`Reductions[NonPV][imp][d][mc] = int(std::round(r));`
`159`	`160`	`Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);`