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Simplified shuffle extension version (#2121)

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only the extension part of the shuffle patch is sufficient to
pass [0,3.5] bounds at VLTC as shown by two more tests.

http://tests.stockfishchess.org/tests/view/5cc168bc0ebc5925cf02bda8
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 120684 W: 17875 L: 17400 D: 85409

http://tests.stockfishchess.org/tests/view/5cc14d510ebc5925cf02bcb5
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 68415 W: 10250 L: 9905 D: 48260

this patch proposes to simplify back to this basic and easier to
understand version. In case there is a need to run a [-3, 1] VLTC on
this one, it can be done, but it is resource intensive, and not needed
IMO.

Bench: 3388643
This commit is contained in:
Joost VandeVondele 2019-05-02 19:22:29 +02:00 • committed by Marco Costalba
parent 7ede1ed071
commit 5c4002aa82
1 changed files with 1 additions and 11 deletions
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12
src/search.cpp
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@ -606,15 +606,6 @@ namespace {
: ttHit ? tte->move() : MOVE_NONE; : ttHit ? tte->move() : MOVE_NONE;
ttPv = (ttHit && tte->is_pv()) || (PvNode && depth > 4 * ONE_PLY); ttPv = (ttHit && tte->is_pv()) || (PvNode && depth > 4 * ONE_PLY);
// If position has been searched at higher depths and we are shuffling,
// return value_draw.
if ( pos.rule50_count() > 36 - 6 * (pos.count<ALL_PIECES>() > 14)
&& ss->ply > 36 - 6 * (pos.count<ALL_PIECES>() > 14)
&& ttHit
&& tte->depth() > depth
&& pos.count<PAWN>() > 0)
return VALUE_DRAW;
// At non-PV nodes we check for an early TT cutoff // At non-PV nodes we check for an early TT cutoff
if ( !PvNode if ( !PvNode
&& ttHit && ttHit
@ -939,9 +930,8 @@ moves_loop: // When in check, search starts from here
// Shuffle extension // Shuffle extension
else if ( PvNode else if ( PvNode
&& pos.rule50_count() > 18 && pos.rule50_count() > 18
&& ss->ply > 18
&& depth < 3 * ONE_PLY && depth < 3 * ONE_PLY
&& ss->ply < 3 * thisThread->rootDepth / ONE_PLY) // To avoid infinite loops && ss->ply < 3 * thisThread->rootDepth / ONE_PLY) // To avoid too deep searches
extension = ONE_PLY; extension = ONE_PLY;
// Passed pawn extension // Passed pawn extension