Increase pawns cache (#2187)
Increase size of the pawns table by the factor 8. This decreases the number of recalculations of pawn structure information significantly (at least at LTC).
I have done measurements for different depths and pawn cache sizes.
First are given the number of pawn entry calculations are done (in parentheses is the frequency that a call to probe triggers a pawn entry calculation). The delta% are the percentage of less done pawn entry calculations in comparison to master
VSTC: bench 1 1 12
STC: bench 8 1 16
LTC: bench 64 1 20
VLTC: bench 512 1 24
VSTC STC LTC VLTC
master 82218(6%) 548935(6%) 2415422(7%) 9548071(7%)
pawncache*2 79859(6%) 492943(5%) 2084794(6%) 8275206(6%)
pawncache*4 78551(6%) 458758(5%) 1827770(5%) 7112531(5%)
pawncache*8 77963(6%) 439421(4%) 1649169(5%) 6128652(4%)
delta%(p2-m) -2.9% -10.2% -13.7% -13.3%
delta%(p4-m) -4.5% -16.4% -24.3% -25.5%
delta%(p8-m) -5.2% -20.0% -31.7% -35.8%
STC: (non-regression test because at STC the effect is smaller than at LTC)
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 22767 W: 5160 L: 5040 D: 12567
http://tests.stockfishchess.org/tests/view/5d00f6040ebc5925cf09c3e2
LTC:
LLR: 2.94 (-2.94,2.94) [0.00,4.00]
Total: 26340 W: 4524 L: 4286 D: 17530
http://tests.stockfishchess.org/tests/view/5d00a3810ebc5925cf09ba16
No functional change.