Include all blockers in king danger

Simplification: in king danger, include all blockers and not only pinned
pieces, since blockers enemy pieces can result in discovered checks which
are also bad.

STC  http://tests.stockfishchess.org/tests/view/5af35f9f0ebc5968e6523fe9
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 145781 W: 29368 L: 29478 D: 86935

LTC http://tests.stockfishchess.org/tests/view/5af3cb430ebc5968e652401f
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 76398 W: 11272 L: 11232 D: 53894

I also incorrectly scheduled STC with [0,5] which it failed.
http://tests.stockfishchess.org/tests/view/5af283c00ebc5968e6523f33
LLR: -2.94 (-2.94,2.94) [0.00,5.00]
Total: 12338 W: 2451 L: 2522 D: 7365

Closes https://github.com/official-stockfish/Stockfish/pull/1593

bench: 4698290

----------------------------------------

Thanks to @vondele and @Rocky640 for a cleaner version of the patch,
and the following comments!

> Most of the pinned, (or for this pull request, blocking) squares were
> already computed in the unsafeChecks, the only missing squares being:
>
> a) squares attacked by a Queen which are occupied by friendly piece
>    or "unsafe". Note that adding such squares never passed SPRT[0,5].
>
> b) squares not in mobilityArea[Us].
>
> There is a strong relationship between the blockers and the unsafeChecks,
> but the bitboard unsafeChecks is still useful when the checker is not
> aligned with the king, and the checking square is occupied by friendly
> piece or is "unsafe". This is always the case for the Knight.

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index d2aab71df68c393c5e0323d87514efdaf523aa64..1d2c5f8e55304c1931790fa45c3649e9ddf0f55c 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -420,7 +420,7 @@ namespace {
                                            : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
 
     const Square ksq = pos.square<KING>(Us);
                                            : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
 
     const Square ksq = pos.square<KING>(Us);

-    Bitboard weak, b, b1, b2, safe, unsafeChecks, pinned;
+    Bitboard weak, b, b1, b2, safe, unsafeChecks;

 
     // King shelter and enemy pawns storm
     Score score = pe->king_safety<Us>(pos, ksq);
 
     // King shelter and enemy pawns storm
     Score score = pe->king_safety<Us>(pos, ksq);


@@ -472,12 +472,11 @@ namespace {
         // Unsafe or occupied checking squares will also be considered, as long as
         // the square is in the attacker's mobility area.
         unsafeChecks &= mobilityArea[Them];
         // Unsafe or occupied checking squares will also be considered, as long as
         // the square is in the attacker's mobility area.
         unsafeChecks &= mobilityArea[Them];

-        pinned = pos.blockers_for_king(Us) & pos.pieces(Us);

 
         kingDanger +=        kingAttackersCount[Them] * kingAttackersWeight[Them]
                      + 102 * kingAttacksCount[Them]
                      + 191 * popcount(kingRing[Us] & weak)
 
         kingDanger +=        kingAttackersCount[Them] * kingAttackersWeight[Them]
                      + 102 * kingAttacksCount[Them]
                      + 191 * popcount(kingRing[Us] & weak)

-                     + 143 * popcount(pinned | unsafeChecks)
+                     + 143 * popcount(pos.blockers_for_king(Us) | unsafeChecks)

                      - 848 * !pos.count<QUEEN>(Them)
                      -   9 * mg_value(score) / 8
                      +  40;
                      - 848 * !pos.count<QUEEN>(Them)
                      -   9 * mg_value(score) / 8
                      +  40;