code: def test_persistent_reduction(self):
      def f(x):
          return x / x.sum(dim=-1, keepdim=True)
  
      with mock.patch.object(
          CoordescTuner,
          "compare_config",
          mock_compare_config_prefer_larger_XBLOCK,
      ):
          x = torch.ones(2, 256).cuda()
          expected = f(x)
          # the first call get correct result when cache miss. Don't know why yet
          _ = torch.compile(f)(x)
          actual = torch.compile(f)(x)
          self.assertTrue(
              torch.allclose(expected, actual, atol=1e-4, rtol=1e-4),
              f"Expected:\n{expected}\nActual:\n{actual}",
          )
  
file_path: pytorch/test/inductor/test_coordinate_descent_tuner.py
imports: import sys
  import unittest
  from unittest import mock
  import torch
  from torch._dynamo.test_case import run_tests, TestCase
  from torch.testing._internal.common_utils import IS_LINUX
  from torch.testing._internal.inductor_utils import HAS_CUDA
  from torch._inductor import config
  from torch._inductor.coordinate_descent_tuner import CoordescTuner
label_desc: Use image node_id 4 for calling the TestCoordinateDescentTuner obj's underlying member method code with example usage: obj.test_persistent_reduction() and returns: unknown