* reworked ddp func to avoid dead locks in tests

* reworked ddp func to avoid dead locks in tests

tests/test_oml/test_ddp/test_loader_patcher.py

@@ -17,7 +17,6 @@
 from .utils import run_in_ddp
 
 
-@pytest.mark.skip(reason="Dead locks may appear when running in CI")
 @pytest.mark.long
 @pytest.mark.parametrize("n_labels_sampler", [2, 5])
 @pytest.mark.parametrize("n_instances_sampler", [2, 5])
@@ -156,7 +155,6 @@ def check_patching_balance_batch_sampler(
     assert len(set(outputs_from_epochs)) == len(outputs_from_epochs)
 
 
-@pytest.mark.skip(reason="Dead locks may appear when running in CI")
 @pytest.mark.long
 @pytest.mark.parametrize("shuffle", [True, False])
 @pytest.mark.parametrize("drop_last", [True, False])

tests/test_oml/test_ddp/utils.py

@@ -1,16 +1,12 @@
 import inspect
-import pickle
-import sys
+import socket
 from datetime import timedelta
-from pathlib import Path
 from typing import Any, Callable, Tuple
 
 import torch
 from torch.distributed import destroy_process_group, init_process_group
 from torch.multiprocessing import spawn
 
-from oml.const import TMP_PATH
-from oml.utils.io import calc_hash
 from oml.utils.misc import set_global_seed
 
 
@@ -23,22 +19,20 @@ def assert_signature(fn: Callable) -> None:  # type: ignore
         raise ValueError(f"The function '{fn.__name__}' should have 'rank' and 'world_size' as the first two arguments")
 
 
-def generate_connection_filename(world_size: int, fn: Callable, *args: Tuple[Any, ...]) -> Path:  # type: ignore
-    python_info = sys.version_info
-    python_str = f"{python_info.major}.{python_info.minor}.{python_info.micro}"
-    args_hash = calc_hash(pickle.dumps(args))
-    filename = TMP_PATH / f"{fn.__name__}_{world_size}_{python_str}_{args_hash}"
-    return filename
+def get_free_port() -> int:
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.bind(("", 0))
+        return s.getsockname()[1]
 
 
 def fn_ddp_wrapper(
-    rank: int, connection_file: Path, world_size: int, fn: Callable, *args: Tuple[Any, ...]  # type: ignore
+    rank: int, port: int, world_size: int, fn: Callable, *args: Tuple[Any, ...]  # type: ignore
 ) -> Any:  # type: ignore
     init_process_group(
         backend="gloo",
         rank=rank,
         world_size=world_size,
-        init_method=f"file://{connection_file}",
+        init_method=f"tcp://127.0.0.1:{port}",
         timeout=timedelta(seconds=120),
     )
     set_global_seed(1)
@@ -50,12 +44,12 @@ def fn_ddp_wrapper(
 
 def run_in_ddp(world_size: int, fn: Callable, args: Tuple[Any, ...] = ()) -> Any:  # type: ignore
     assert_signature(fn)
+    set_global_seed(1)
+    torch.set_num_threads(1)
     if world_size > 1:
-        connection_file = generate_connection_filename(world_size, fn, *args)
-        connection_file.unlink(missing_ok=True)
-        connection_file.parent.mkdir(exist_ok=True, parents=True)
+        port = get_free_port()
         # note, 'spawn' automatically passes 'rank' to its first argument
-        spawn(fn_ddp_wrapper, args=(connection_file, world_size, fn, *args), nprocs=world_size, join=True)
+        spawn(fn_ddp_wrapper, args=(port, world_size, fn, *args), nprocs=world_size, join=True)
     else:
         set_global_seed(1)
         return fn(0, world_size, *args)