Dynamic draw value

joergoster · mcostalba · commit b917cd275e6f · 2014-02-26T19:33:52.000+01:00
Try to avoid repetition draws at early midgame,
this should give an edge against weaker opponents
and reduce draw rate.

Tested for regressions with SPRT[-3, 1] and
passed both short TC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 68498 W: 12928 L: 12891 D: 42679

And long TC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 40212 W: 6386 L: 6295 D: 27531

bench: 7990513
diff --git a/src/search.cpp b/src/search.cpp
@@ -206,10 +206,10 @@ void Search::think() {
       }
   }
 
-  if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"])
+  if (!Options["UCI_AnalyseMode"])
   {
-      int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns
-      cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase
+      // Dynamic draw value: try to avoid repetition draws at early midgame
+      int cf = std::max(70 - RootPos.game_ply(), 0);
       DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
       DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
   }

Original file line number	Diff line number	Diff line change
`@@ -206,10 +206,10 @@ void Search::think() {`
`206`	`206`	`}`
`207`	`207`	`}`
`208`	`208`
`209`		`- if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"])`
	`209`	`+ if (!Options["UCI_AnalyseMode"])`
`210`	`210`	`{`
`211`		`- int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns`
`212`		`- cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase`
	`211`	`+ // Dynamic draw value: try to avoid repetition draws at early midgame`
	`212`	`+ int cf = std::max(70 - RootPos.game_ply(), 0);`
`213`	`213`	`DrawValue[ RootColor] = VALUE_DRAW - Value(cf);`
`214`	`214`	`DrawValue[~RootColor] = VALUE_DRAW + Value(cf);`
`215`	`215`	`}`