Latest abrok Development Version September 23rd 2021 (SF The gift that keeps on giving

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Author: Stéphane Nicolet
Date: Thu Sep 23 23:24:28 2021 +0200
Timestamp: 1632432268

Tweak doubly singular condition (Topo's patch)

This patch relax a little bit the condition for doubly singular moves
(ie moves that are so forced that we think that they deserve a local
double extension of the search). We lower the margin and allow up to
six such double extensions in the path between the root and the critical
node.

Original idea by Siad Daboul (@TopoIogist) in PR #3709

Tested with the previous commit:

passed STC:
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 33048 W: 8458 L: 8236 D: 16354 Elo +2.33
Ptnml(0-2): 120, 3701, 8660, 3923, 120
https://tests.stockfishchess.org/tests/view/614b24347bdc23e77ceb88fe

passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,3.50>
Total: 54176 W: 13712 L: 13406 D: 27058 Elo +1.96
Ptnml(0-2): 36, 5653, 15399, 5969, 31
https://tests.stockfishchess.org/tests/view/614b3b727bdc23e77ceb8911

closes https://github.com/official-stockfish/Stockfish/pull/3714

Bench: 5792377
see source