Reduce VALUE_KNOWN_WIN to 10000

uriblass · mcostalba · commit 93f95cc93669 · 2014-01-27T20:09:51.000+01:00
With some positions like

8/8/8/2p2K2/1pp5/br1p1b2/2p2r2/qqkqq3 w - -

The eval score is higher than VALUE_INFINITE because
is the sum of VALUE_KNOWN_WIN plus a big material
advantage. This leads to an assert. Here are the
steps to reproduce:

Compile SF with debug=yes then do

./stockfish
position fen 8/8/8/2p2K2/1pp5/br1p1b2/2p2r2/qqkqq3 w - -
go depth 1

This patch fixes the issue in this case, but do exsist
other positions for which the patch is not enough and
we will need to limit the eval score to be sure not
overflow the limit.

Note that is not possible to increase the value of
VALUE_INFINITE because should remain within int16_t
type to be stored in a TT entry.

bench: 7356053
diff --git a/src/types.h b/src/types.h
@@ -155,7 +155,7 @@ enum Bound {
 enum Value {
   VALUE_ZERO      = 0,
   VALUE_DRAW      = 0,
-  VALUE_KNOWN_WIN = 15000,
+  VALUE_KNOWN_WIN = 10000,
   VALUE_MATE      = 30000,
   VALUE_INFINITE  = 30001,
   VALUE_NONE      = 30002,
