From: mstembera <MissingEmail@email>
Date: Sun, 5 Jul 2020 22:17:04 +0000 (-0700)
Subject: Simplify make_promotions()
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=bf5ce1c214f8f8e3f98e5e3ac43db0dd28617e35

Simplify make_promotions()

Remove special case handling of QUIET_CHECKS in make_promotions()

STC https://tests.stockfishchess.org/tests/view/5f055dbb59f6f035328945fb
LLR: 2.98 (-2.94,2.94) {-1.50,0.50}
Total: 42808 W: 8177 L: 8054 D: 26577
Ptnml(0-2): 665, 4890, 10201, 4953, 695

LTC https://tests.stockfishchess.org/tests/view/5f06231a59f6f03532894661
LLR: 2.96 (-2.94,2.94) {-1.50,0.50}
Total: 9616 W: 1214 L: 1111 D: 7291
Ptnml(0-2): 53, 821, 2965, 908, 61

closes https://github.com/official-stockfish/Stockfish/pull/2800

Bench: 4576410
---

diff --git a/src/movegen.cpp b/src/movegen.cpp
index 17203a95..4ff12fc6 100644
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -29,22 +29,20 @@ namespace {
   ExtMove* make_promotions(ExtMove* moveList, Square to, Square ksq) {
 
     if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
+    {
         *moveList++ = make<PROMOTION>(to - D, to, QUEEN);
+        if (attacks_bb<KNIGHT>(to) & ksq)
+            *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
+    }
 
     if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
     {
         *moveList++ = make<PROMOTION>(to - D, to, ROOK);
         *moveList++ = make<PROMOTION>(to - D, to, BISHOP);
-        *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
+        if (!(attacks_bb<KNIGHT>(to) & ksq))
+            *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
     }
 
-    // Knight promotion is the only promotion that can give a direct check
-    // that's not already included in the queen promotion.
-    if (Type == QUIET_CHECKS && (attacks_bb<KNIGHT>(to) & ksq))
-        *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
-    else
-        (void)ksq; // Silence a warning under MSVC
-
     return moveList;
   }
 
@@ -263,8 +261,8 @@ namespace {
 } // namespace
 
 
-/// <CAPTURES>     Generates all pseudo-legal captures and queen promotions
-/// <QUIETS>       Generates all pseudo-legal non-captures and underpromotions
+/// <CAPTURES>     Generates all pseudo-legal captures plus queen and checking knight promotions
+/// <QUIETS>       Generates all pseudo-legal non-captures and underpromotions(except checking knight)
 /// <NON_EVASIONS> Generates all pseudo-legal captures and non-captures
 ///
 /// Returns a pointer to the end of the move list.
@@ -287,8 +285,8 @@ template ExtMove* generate<QUIETS>(const Position&, ExtMove*);
 template ExtMove* generate<NON_EVASIONS>(const Position&, ExtMove*);
 
 
-/// generate<QUIET_CHECKS> generates all pseudo-legal non-captures and knight
-/// underpromotions that give check. Returns a pointer to the end of the move list.
+/// generate<QUIET_CHECKS> generates all pseudo-legal non-captures.
+/// Returns a pointer to the end of the move list.
 template<>
 ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
 
diff --git a/src/search.cpp b/src/search.cpp
index f14bdf77..1610c206 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1486,8 +1486,8 @@ moves_loop: // When in check, search starts from here
 
     // Initialize a MovePicker object for the current position, and prepare
     // to search the moves. Because the depth is <= 0 here, only captures,
-    // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
-    // be generated.
+    // queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS)
+    // will be generated.
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
                                       &thisThread->captureHistory,
                                       contHist,