w

flash/core/data/datamodule.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import os
+import platform
 from typing import Any, Optional
 
 import pytorch_lightning as pl
@@ -64,10 +65,10 @@ def __init__(
 
         # TODO: figure out best solution for setting num_workers
         if num_workers is None:
-            num_workers = os.cpu_count()
-        # if num_workers is None:
-        #     #    warnings.warn("Could not infer cpu count automatically, setting it to zero")
-        #     num_workers = 0
+            if platform.system() == "Darwin":
+                num_workers = 0
+            else:
+                num_workers = os.cpu_count()
         self.num_workers = num_workers
 
         self._data_pipeline = None

tests/core/test_data.py

@@ -11,6 +11,8 @@
 # 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.
+import platform
+
 import torch
 
 from flash import DataModule
@@ -55,7 +57,10 @@ def test_cpu_count_none():
     train_ds = DummyDataset()
     # with patch("os.cpu_count", return_value=None), pytest.warns(UserWarning, match="Could not infer"):
     dm = DataModule(train_ds, num_workers=None)
-    assert dm.num_workers > 0
+    if platform.system() == "Darwin":
+        assert dm.num_workers == 0
+    else:
+        assert dm.num_workers > 0
 
 
 def test_pipeline():