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Use 'in <literal>' instead of str.isupper/isspace/islower in gen_moves (+3.7% nps) #132

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Use 'in <literal>' instead of str.isupper/isspace/islower in gen_moves (+3.7% nps) #132

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9 changes: 6 additions & 3 deletions sunfish.py
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Original file line number Diff line number Diff line change
Expand Up @@ -154,14 +154,17 @@ def gen_moves(self):
# For each of our pieces, iterate through each possible 'ray' of moves,
# as defined in the 'directions' map. The rays are broken e.g. by
# captures or immediately in case of pieces such as knights.
# NB: `in <literal-str>` is ~30% faster than the equivalent .isupper() /
# .isspace() / .islower() method calls in CPython; this matters because
# these checks run millions of times per search.
for i, p in enumerate(self.board):
if not p.isupper():
if p not in "PNBRQK":
continue
for d in directions[p]:
for j in count(i + d, d):
q = self.board[j]
# Stay inside the board, and off friendly pieces
if q.isspace() or q.isupper():
if q in " \nPNBRQK":
break
# Pawn move, double move and capture
if p == "P":
Expand All @@ -182,7 +185,7 @@ def gen_moves(self):
# Move it
yield Move(i, j, "")
# Stop crawlers from sliding, and sliding after captures
if p in "PNK" or q.islower():
if p in "PNK" or q in "pnbrqk":
break
# Castling, by sliding the rook next to the king
if i == A1 and self.board[j + E] == "K" and self.wc[0]:
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