Use a lower stat score threshold of 22500.
Failed yellow at STC after many games (~0.92 Elo):
LLR: -2.96 (-2.94,2.94) [0.00,4.00]
Total: 73978 W: 14947 L: 14834 D: 44197
http://tests.stockfishchess.org/tests/view/
5af2deec0ebc5968e6523f80
But scales good and passed LTC:
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 23147 W: 3453 L: 3237 D: 16457
http://tests.stockfishchess.org/tests/view/
5af3cf820ebc5968e6524022
Closes https://github.com/official-stockfish/Stockfish/pull/1591
Bench:
4777674
// Step 9. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
- && (ss-1)->statScore < 30000
+ && (ss-1)->statScore < 22500
&& eval >= beta
&& ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
&& !ss->excludedMove