code: def testRingPermutations(self):
      # 0 devices
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(1, 0, [])
      self.assertEqual(pred_by_c_d, [])
      self.assertEqual(rank_by_c_d, [])
      # 1 worker, 1 subchunk cases
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(1, 1, [0])
      self.assertEqual(pred_by_c_d, [[0]])
      self.assertEqual(rank_by_c_d, [[0]])
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(1, 1, [0, 1, 2])
      self.assertEqual(pred_by_c_d, [[2, 0, 1]])
      self.assertEqual(rank_by_c_d, [[0, 1, 2]])
      # multiple workers, 1 subchunk cases
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(2, 1, [0, 1, 2])
      self.assertEqual(pred_by_c_d, [[5, 0, 1, 2, 3, 4]])
      self.assertEqual(rank_by_c_d, [[0, 1, 2, 3, 4, 5]])
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(3, 1, [0, 1, 2])
      self.assertEqual(pred_by_c_d, [[8, 0, 1, 2, 3, 4, 5, 6, 7]])
      self.assertEqual(rank_by_c_d, [[0, 1, 2, 3, 4, 5, 6, 7, 8]])
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(2, 1, [2, 1, 0])
      self.assertEqual(pred_by_c_d, [[1, 2, 3, 4, 5, 0]])
      self.assertEqual(rank_by_c_d, [[2, 1, 0, 5, 4, 3]])
      # 1 worker, multiple subchunk cases
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(
          1, 2, [0, 1, 2, 3]
      )
      self.assertEqual(pred_by_c_d, [[3, 0, 1, 2], [3, 0, 1, 2]])
      self.assertEqual(rank_by_c_d, [[0, 1, 2, 3], [2, 3, 0, 1]])
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(
          1, 4, [0, 1, 2, 3]
      )
      self.assertEqual(
          pred_by_c_d,
          [[3, 0, 1, 2], [3, 0, 1, 2], [3, 0, 1, 2], [3, 0, 1, 2]],
      )
      self.assertEqual(
          rank_by_c_d,
          [[0, 1, 2, 3], [3, 0, 1, 2], [2, 3, 0, 1], [1, 2, 3, 0]],
      )
      # multiple worker, multiple subchunk cases
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(
          2, 2, [0, 1, 2, 3]
      )
      self.assertEqual(
          pred_by_c_d,
          [[7, 0, 1, 2, 3, 4, 5, 6], [3, 0, 5, 2, 7, 4, 1, 6]],
      )
      self.assertEqual(
          rank_by_c_d,
          [[0, 1, 2, 3, 4, 5, 6, 7], [2, 3, 0, 1, 6, 7, 4, 5]],
      )
      pred_by_c_d, rank_by_c_d = ar._ring_permutations(
          2, 2, [0, 3, 2, 1]
      )
      self.assertEqual(
          pred_by_c_d,
          [[5, 2, 3, 0, 1, 6, 7, 4], [1, 2, 7, 0, 5, 6, 3, 4]],
      )
      self.assertEqual(
          rank_by_c_d,
          [[0, 3, 2, 1, 4, 7, 6, 5], [2, 1, 0, 3, 6, 5, 4, 7]],
      )
  
imports: import time
  import numpy
  from tensorflow.core.framework import types_pb2
  from tensorflow.python.distribute.v1 import all_reduce
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import state_ops
  from tensorflow.python.platform import test
  from tensorflow.python.platform import tf_logging
label_desc: Use image node_id 2 for calling the AllReduceTest obj's underlying member method code with example usage: obj.testRingPermutations() without return types