Add parse for PrefLib data files.

PiperOrigin-RevId: 597287351
Change-Id: Ica9550288e611f54187f63f88167dd4c47c87004

open_spiel/python/voting/preflib_util.py

@@ -0,0 +1,79 @@
+# Copyright 2023 DeepMind Technologies Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Helpers to work with PrefLib data."""
+
+import pyspiel
+from open_spiel.python.voting import base
+
+
+def parse_preflib_data(string_data: str) -> base.PreferenceProfile:
+  """Parses the contents of a PrefLib data file.
+
+  Currently only supports SOC and SOI. See https://www.preflib.org/format.
+
+  Args:
+    string_data: the name of the file to parse.
+
+  Returns:
+    A preference profile.
+  """
+  lines = string_data.split("\n")
+  alternatives = []
+  num_alternatives = None
+  num_votes = None
+  profile = base.PreferenceProfile()
+  for raw_line in lines:
+    line = raw_line.strip()
+    if not line: continue
+    if line.startswith("#"):
+      parts = line.split(" ")
+      if line.startswith("# DATA TYPE: "):
+        assert(parts[3] == "soc" or parts[3] == "soi")
+      elif line.startswith("# NUMBER ALTERNATIVES:"):
+        num_alternatives = int(parts[3])
+        alternatives = [None] * num_alternatives
+      elif line.startswith("# NUMBER VOTERS:"):
+        num_votes = int(parts[3])
+      elif line.startswith("# ALTERNATIVE NAME "):
+        num = int(parts[3].split(":")[0])
+        index_of_colon = line.index(":")
+        assert 1 <= num <= num_alternatives
+        alternatives[num-1] = line[index_of_colon+2:]
+    else:
+      if profile.num_alternatives() == 0:
+        profile = base.PreferenceProfile(alternatives=alternatives)
+      index_of_colon = line.index(":")
+      weight = int(line[:index_of_colon])
+      vote_parts = line[index_of_colon+2:].split(",")
+      vote = [alternatives[int(part) - 1] for part in vote_parts]
+      if weight > 0:
+        profile.add_vote(vote, weight)
+  assert num_votes == profile.num_votes()
+  return profile
+
+
+def parse_preflib_datafile(filename: str) -> base.PreferenceProfile:
+  """Parses a Preflib data file.
+
+  Currently only supports SOC and SOI. See https://www.preflib.org/format.
+
+  Args:
+    filename: the name of the file to parse.
+
+  Returns:
+    A preference profile.
+  """
+  contents = pyspiel.read_contents_from_file(filename, "r")
+  return parse_preflib_data(contents)

open_spiel/python/voting/preflib_util_test.py

@@ -0,0 +1,60 @@
+# Copyright 2023 DeepMind Technologies Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for open_spiel.python.voting.util."""
+
+from absl.testing import absltest
+from open_spiel.python.voting import preflib_util
+
+TEST_DATA = """
+# FILE NAME: 00004-00000050.soc
+# TITLE: Netflix Prize Data
+# DESCRIPTION:
+# DATA TYPE: soc
+# MODIFICATION TYPE: induced
+# RELATES TO:
+# RELATED FILES:
+# PUBLICATION DATE: 2013-08-17
+# MODIFICATION DATE: 2022-09-16
+# NUMBER ALTERNATIVES: 3
+# NUMBER VOTERS: 391
+# NUMBER UNIQUE ORDERS: 6
+# ALTERNATIVE NAME 1: The Amityville Horror
+# ALTERNATIVE NAME 2: Mars Attacks!
+# ALTERNATIVE NAME 3: Lean on Me
+186: 3,1,2
+71: 1,3,2
+58: 3,2,1
+45: 2,3,1
+18: 1,2,3
+13: 2,1,3
+"""
+
+
+class UtilTest(absltest.TestCase):
+  def test_load_preflib(self):
+    print(TEST_DATA)
+    profile = preflib_util.parse_preflib_data(TEST_DATA)
+    print(profile)
+    self.assertEqual(profile.num_alternatives(), 3)
+    self.assertEqual(profile.num_votes(), 391)
+    self.assertListEqual(profile.alternatives, [
+        "The Amityville Horror", "Mars Attacks!", "Lean on Me"
+    ])
+    print(profile.alternatives)
+    print(profile.margin_matrix())
+
+
+if __name__ == "__main__":
+  absltest.main()