Less NMP if the position was previously in PV.
author31m059 <37052095+31m059@users.noreply.github.com>
Tue, 28 Jan 2020 01:48:01 +0000 (20:48 -0500)
committerJoost VandeVondele <Joost.VandeVondele@gmail.com>
Tue, 28 Jan 2020 09:31:25 +0000 (10:31 +0100)
commitd878bc8cda47044f4db37a954f25e6122dc0d0ca
tree8d01afa3ef17654c554910087bee3187d42d3e09
parent1d3efff47274bd03d4deced8d7ba0360bd1dba8a
Less NMP if the position was previously in PV.

The intention of the patch is to avoid aggressive null move pruning (NMP)
in positions that have previously been found to be important (PV nodes).
If we already do not apply NMP for current PV nodes, it makes sense to apply
it less often for positions that have previously been PV nodes too.

STC:
LLR: 2.96 (-2.94,2.94) {-1.00,3.00}
Total: 14959 W: 2921 L: 2782 D: 9256
Ptnml(0-2): 254, 1679, 3493, 1762, 282
http://tests.stockfishchess.org/tests/view/5e2f6637ab2d69d58394fcfd

LTC:
LLR: 2.95 (-2.94,2.94) {0.00,2.00}
Total: 6442 W: 899 L: 753 D: 4790
Ptnml(0-2): 42, 549, 1885, 659, 61
http://tests.stockfishchess.org/tests/view/5e2f767bab2d69d58394fd04

closes https://github.com/official-stockfish/Stockfish/pull/2525

Bench: 4725546
src/search.cpp