- // Loop through all legal moves
- CheckInfo ci(pos);
- for (MoveStack* cur = mlist; cur != last; cur++)
- {
- m = cur->move;
- pos.do_move(m, st, ci, pos.move_is_check(m, ci));
- sum += perft(pos, depth - ONE_PLY);
- pos.undo_move(m);
- }
- return sum;
+ MoveStack mlist[MOVES_MAX];
+ StateInfo st;
+ Move m;
+ int64_t sum = 0;
+
+ // Generate all legal moves
+ MoveStack* last = generate<MV_LEGAL>(pos, mlist);
+
+ // If we are at the last ply we don't need to do and undo
+ // the moves, just to count them.
+ if (depth <= ONE_PLY)
+ return int(last - mlist);
+
+ // Loop through all legal moves
+ CheckInfo ci(pos);
+ for (MoveStack* cur = mlist; cur != last; cur++)
+ {
+ m = cur->move;
+ pos.do_move(m, st, ci, pos.move_is_check(m, ci));
+ sum += perft(pos, depth - ONE_PLY);
+ pos.undo_move(m);
+ }
+ return sum;