From 85eabc238f1604fdd09cf94cf2e40c6e3d68f98b Mon Sep 17 00:00:00 2001
From: Ihor Indyk <iindyk@google.com>
Date: Thu, 19 Feb 2026 21:03:28 -0800
Subject: [PATCH] Remove unused pure python implementation for index shuffle.

PiperOrigin-RevId: 872699971
---
 .../python/index_shuffle_python.py            | 79 -------------------
 .../python/index_shuffle_python_test.py       | 50 ------------
 2 files changed, 129 deletions(-)
 delete mode 100644 grain/_src/python/experimental/index_shuffle/python/index_shuffle_python.py
 delete mode 100644 grain/_src/python/experimental/index_shuffle/python/index_shuffle_python_test.py

diff --git a/grain/_src/python/experimental/index_shuffle/python/index_shuffle_python.py b/grain/_src/python/experimental/index_shuffle/python/index_shuffle_python.py
deleted file mode 100644
index 6184f7f29..000000000
--- a/grain/_src/python/experimental/index_shuffle/python/index_shuffle_python.py
+++ /dev/null
@@ -1,79 +0,0 @@
-# Copyright 2023 Google LLC
-#
-# 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
-#
-#     https://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.
-"""Pure Python version of `index_shuffle`.
-
-This is roughly 10x slower than the C++ index_shuffle but still sufficiently
-fast for many use cases. Use it if the C++ version (and it's CLIF wrapper) don't
-work for you.
-"""
-
-import hashlib
-
-
-def _fingerprint(*args) -> int:
-  """A 128-bit fingerprint based on md5.
-
-  For data shuffling - not for cryptography.
-
-  Args:
-    *args: any argument list that can be converted to a string
-
-  Returns:
-    an integer in [0, 2 ** 128)
-  """
-  return int.from_bytes(hashlib.md5(str(args).encode()).digest(), "little")
-
-
-def index_shuffle(index: int, max_index: int, seed: int, rounds: int) -> int:
-  """computes the position of `index` after a pseudorandom permutation on `[0, max_index])`.
-
-  Based on Feistel ciphers.
-
-  For data shuffling - not for cryptography.
-
-  if i != j, then
-  pseudorandom_permutation(n, i, seed) != pseudorandom_permutation(n, j, seed)
-
-  Args:
-    index: an integer in [0, max_index)
-    max_index: A positive integer.
-    seed: A posivtive integer used as seed for the pseudorandom permutation.
-    rounds: Ignored. For compatibility with C++ version.
-
-  Returns:
-    An integer in [0, max_index].
-  """
-  del rounds
-  if not isinstance(max_index, int):
-    raise ValueError("n must be an integer")
-
-  if index < 0 or index > max_index:
-    raise ValueError("out of range")
-
-  if max_index == 1:
-    return 0
-
-  # smallest k such that max_index fits in 2k bits
-  k = (max_index.bit_length() + 1) // 2
-  assert max_index <= 4**k
-  # Permute repeatedly in [max_index, 4 ** k) until you land back in
-  # [0, max_index]. This constitutes a permutation of [0, max_index].
-  while True:
-    # Feistel ciper on 2k bits - i.e. a permutation of [0, 4 ** k)
-    a, b = index // (2**k), index % (2**k)
-    for r in range(3):
-      a, b = b, a ^ (_fingerprint(b, r, seed) % (2**k))
-    index = a * (2**k) + b
-    if index <= max_index:
-      return int(index)
diff --git a/grain/_src/python/experimental/index_shuffle/python/index_shuffle_python_test.py b/grain/_src/python/experimental/index_shuffle/python/index_shuffle_python_test.py
deleted file mode 100644
index bb6fb98c9..000000000
--- a/grain/_src/python/experimental/index_shuffle/python/index_shuffle_python_test.py
+++ /dev/null
@@ -1,50 +0,0 @@
-# Copyright 2023 Google LLC
-#
-# 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
-#
-#     https://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.
-"""Minimal unit test for the Python wrapper of index_shuffle."""
-
-from absl.testing import absltest
-from grain._src.python.experimental.index_shuffle.python import index_shuffle_python
-
-
-class IndexShuffleTest(absltest.TestCase):
-
-  def test_index_shuffle(self):
-    max_index = 46_204
-    seen = set()
-    for x in range(max_index + 1):
-      y = index_shuffle_python.index_shuffle(x, max_index, seed=52, rounds=4)
-      self.assertBetween(y, 0, max_index)
-      seen.add(y)
-    self.assertLen(seen, max_index + 1)
-
-  def test_index_shuffle_huge_number(self):
-    max_index = 1_234_567_891
-    seen = set()
-    for x in range(10_000):
-      y = index_shuffle_python.index_shuffle(x, max_index, seed=27, rounds=4)
-      self.assertBetween(y, 0, max_index)
-      seen.add(y)
-    self.assertLen(seen, 10_000)
-
-  def test_index_shuffle_single_record(self):
-    self.assertEqual(
-        0,
-        index_shuffle_python.index_shuffle(
-            index=0, max_index=0, seed=0, rounds=4
-        ),
-    )
-
-
-if __name__ == '__main__':
-  absltest.main()