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fix: set multiprocessing start method to 'fork' in pt env (since python3.14 defaults to forkserver) #5019

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Merged
njzjz merged 3 commits into from
Nov 30, 2025
Merged

fix: set multiprocessing start method to 'fork' in pt env (since python3.14 defaults to forkserver) #5019

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92c3cbc
fix: set multiprocessing start method to 'fork' in main function(pyth…
OutisLi Oct 20, 2025
83ad632
refactor and exclude windows
OutisLi Oct 20, 2025
c863724
set multiprocessing start method in env not cli entry
OutisLi Nov 27, 2025
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13 changes: 12 additions & 1 deletion deepmd/pt/utils/env.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
import logging
import multiprocessing
import os
import sys

import numpy as np
import torch
Expand All @@ -16,6 +17,17 @@
set_default_nthreads,
)

log = logging.getLogger(__name__)

if sys.platform != "win32":
try:
multiprocessing.set_start_method("fork", force=True)
log.debug("Successfully set multiprocessing start method to 'fork'.")
except (RuntimeError, ValueError) as err:
log.warning(f"Could not set multiprocessing start method: {err}")
else:
log.debug("Skipping fork start method on Windows (not supported).")

SAMPLER_RECORD = os.environ.get("SAMPLER_RECORD", False)
DP_DTYPE_PROMOTION_STRICT = os.environ.get("DP_DTYPE_PROMOTION_STRICT", "0") == "1"
try:
Expand All @@ -26,7 +38,6 @@
NUM_WORKERS = int(os.environ.get("NUM_WORKERS", min(4, ncpus)))
if multiprocessing.get_start_method() != "fork":
# spawn or forkserver does not support NUM_WORKERS > 0 for DataLoader
log = logging.getLogger(__name__)
log.warning(
"NUM_WORKERS > 0 is not supported with spawn or forkserver start method. "
"Setting NUM_WORKERS to 0."
Expand Down