Update distributed.py

Author: ananthsub

tests/utilities/distributed.py

@@ -16,6 +16,7 @@
 import sys
 from pathlib import Path
 from subprocess import TimeoutExpired
+from unittest import mock
 
 import pytorch_lightning
 
@@ -42,3 +43,48 @@ def call_training_script(module_file, cli_args, method, tmpdir, timeout=60):
         p.kill()
         std, err = p.communicate()
     return std, err
+
+
+@mock.patch.dict(os.environ, {"SLURM_PROCID": "0"})
+def test_rank_zero_slurm():
+    """ Test that SLURM environment variables are properly checked for rank_zero_only. """
+    from pytorch_lightning.utilities.distributed import _get_rank, rank_zero_only
+    rank_zero_only.rank = _get_rank()
+
+    @rank_zero_only
+    def foo():
+        # The return type is optional because on non-zero ranks it will not be called
+        return 1
+
+    x = foo()
+    assert x == 1
+
+
+@mock.patch.dict(os.environ, {"RANK": "0"})
+def test_rank_zero_torchelastic():
+    """ Test that torchelastic environment variables are properly checked for rank_zero_only. """
+    from pytorch_lightning.utilities.distributed import _get_rank, rank_zero_only
+    rank_zero_only.rank = _get_rank()
+
+    @rank_zero_only
+    def foo():
+        # The return type is optional because on non-zero ranks it will not be called
+        return 1
+
+    x = foo()
+    assert x == 1
+
+
+@mock.patch.dict(os.environ, {"RANK": "1", "SLURM_PROCID": "2", "LOCAL_RANK": "3"})
+def test_rank_zero_none_set():
+    """ Test that function is not called when rank environment variables are not global zero. """
+
+    from pytorch_lightning.utilities.distributed import _get_rank, rank_zero_only
+    rank_zero_only.rank = _get_rank()
+
+    @rank_zero_only
+    def foo():
+        return 1
+
+    x = foo()
+    assert x is None