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Simplify Passed Pawns (#2058)

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This is a non-functional simplification/speedup.

The truth-table for popcount(support) >= popcount(lever) - 1 is:
------------------lever
------------------0-------1---------2
support--0------X-------X---------0
-----------1------X-------X---------X
-----------2------X-------X---------X

Thus, it is functionally equivalent to just do: support || !more_than_one(lever) which removes the expensive popcounts and the -1.

Result of 20 runs:
base (...h_master.exe) = 1451680 +/- 8202
test (./stockfish ) = 1454781 +/- 8604
diff = +3101 +/- 931

STC
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 35424 W: 7768 L: 7674 D: 19982
Http://tests.stockfishchess.org/tests/view/5c970f170ebc5925cfff5e28

No functional change.
This commit is contained in:
protonspring 2019-03-24 10:37:38 -06:00 • committed by Marco Costalba
parent d320de7619
commit ea5505821d
1 changed files with 1 additions and 1 deletions
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2
src/pawns.cpp
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@ -114,7 +114,7 @@ namespace {
// which could become passed after one or two pawn pushes when are
// not attacked more times than defended.
if ( !(stoppers ^ lever ^ leverPush)
&& popcount(support) >= popcount(lever) - 1
&& (support || !more_than_one(lever))
&& popcount(phalanx) >= popcount(leverPush))
e->passedPawns[Us] |= s;