Change the internal iterative deepening margin from +256 to +128.
Passed STC:
LLR: 3.26 (-2.94,2.94) [0.00,5.00]
Total: 22006 W: 4646 L: 4400 D: 12960
http://tests.stockfishchess.org/tests/view/
5ab54a240ebc590295d8847d
Passed LTC:
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 46665 W: 7187 L: 6898 D: 32580
http://tests.stockfishchess.org/tests/view/
5ab5ba690ebc590295d884b4
Possible work in this area after this change:
• Reduce even more the margin?
• Try to do IID for smaller depths too?
Bench:
5851102
// Step 11. Internal iterative deepening (skipped when in check)
if ( depth >= 6 * ONE_PLY
&& !ttMove
- && (PvNode || ss->staticEval + 256 >= beta))
+ && (PvNode || ss->staticEval + 128 >= beta))
{
Depth d = 3 * depth / 4 - 2 * ONE_PLY;
search<NT>(pos, ss, alpha, beta, d, cutNode, true);