rewrote collinearN code. other connect optimizations

src/evaluate.cpp

@@ -1281,7 +1281,7 @@ namespace {
     }
 
     // Connect-n
-    if (pos.connect_n() > 0)
+    if (pos.connect_n() > 0 && (pos.variant()->connectValue != VALUE_DRAW))
     {
         //Calculate eligible pieces for connection once.
         //Still consider all opponent pieces as blocking.

src/position.cpp

@@ -2801,7 +2801,7 @@ bool Position::is_immediate_game_end(Value& result, int ply) const {
   connectPieces &= pieces(~sideToMove);
 
   // Connect-n
-  if (connect_n() > 0)
+  if ((connect_n() > 0) && (popcount(connectPieces) >= connect_n()))
   {
       Bitboard b;
 
@@ -2843,8 +2843,8 @@ bool Position::is_immediate_game_end(Value& result, int ply) const {
           current |= newBitboard;
       }
   }
-  
-  if (connect_nxn())
+
+  if ((connect_nxn()) && (popcount(connectPieces) >= connect_nxn() * connect_nxn()))
   {
       Bitboard connectors = connectPieces;
       for (int i = 1; i < connect_nxn() && connectors; i++)
@@ -2858,27 +2858,37 @@ bool Position::is_immediate_game_end(Value& result, int ply) const {
 
   // Collinear-n
   if (collinear_n() > 0) {
-      Bitboard allPieces = connectPieces;
-      for (Direction d : var->connect_directions) {
-          Bitboard b = allPieces;
-          while (b) {
-              Square s = pop_lsb(b);
-
-              int total_count = 1; // Start with the current piece
-
-              // Check in both directions
-              for (int sign : {-1, 1}) {
-                  Bitboard shifted = shift(sign * d, square_bb(s));
-                  while (shifted) {
-                      if (shifted & b) {
-                          total_count++;
-                          b &= ~shifted; // Remove this piece from further consideration
-                      }
-                      shifted = shift(sign * d, shifted);
-                  }
-              }
-
-              if (total_count >= collinear_n()) {
+      Bitboard pieces = connectPieces;
+      while (pieces) {
+          if (popcount(pieces) < collinear_n()) {
+              break; // Early out to the next section
+          }
+          //Use pop_lsb to loop through the pieces. Then for each of the directions,
+          //use line_bb to calculate the entire row, column or diagonal that contains
+          //the piece and the shifted square, then use popcount to count the number
+          //of pieces on that line.
+          Square s = pop_lsb(pieces);
+          for (Direction d : var->connect_directions) {
+              Square shifted_square = s + d;
+
+
+              if (!is_ok(shifted_square)) continue; //This is totally fine.
+              //Pieces where the shift is outside the board will not be processed
+              //for that direction, but in order to be collinear with another piece,
+              //there would be another piece that counts it as part of its line.
+              //Even if say, all the pieces were on the EAST edge, it's the NORTH
+              //direction that would count them up.
+              //Only exception is that if collinearN was set to 1, and there was 1
+              //piece on the NORTH_EAST corner, it wouldn't count. Possible solutions:
+              //1. Ignore
+              //2. Tell user that collinearN=1 is silly, use flagPieces or connectN
+              //3. Special case here to check
+              //4. Quietly convert it to connectN=1
+
+
+              Bitboard line = line_bb(s, shifted_square);
+              int piece_count = popcount(line & connectPieces);
+              if (piece_count >= collinear_n()) {
                   result = convert_mate_value(-var->connectValue, ply);
                   return true;
               }