fix test_gen_nccl_id_op failed (#30686)

python/paddle/fluid/tests/unittests/test_gen_nccl_id_op.py

@@ -16,6 +16,7 @@ import unittest
 import os
 import copy
 from launch_function_helper import wait, _find_free_port
+from multiprocessing import Pool, Process
 from threading import Thread
 
 os.environ['GLOG_vmodule'] = str("gen_nccl_id_op*=10,gen_comm_id*=10")
@@ -30,8 +31,8 @@ def run_gen_ncc_id(attr):
     nccl_comm_num = attr['nccl_comm_num']
     use_hallreduce = attr['use_hierarchical_allreduce']
 
-    startup_program = paddle.static.Program()
-    main_program = paddle.static.Program()
+    startup_program = paddle.static.default_startup_program()
+    main_program = paddle.static.default_main_program()
 
     with paddle.static.program_guard(main_program, startup_program):
         nccl_id_var = startup_program.global_block().create_var(
@@ -62,8 +63,6 @@ def run_gen_ncc_id(attr):
 
     place = paddle.CPUPlace()
     exe = paddle.static.Executor(place)
-    scope = paddle.static.Scope()
-    with paddle.static.scope_guard(scope):
     exe.run(startup_program)
 
 
@@ -99,13 +98,12 @@ class TestGenNcclIdOp(unittest.TestCase):
         procs = []
         for i in range(nranks):
             attr['trainer_id'] = i
-            # NOTE. multiprocessing cannot be covered by coverage
-            p = Thread(target=run_gen_ncc_id, args=(copy.copy(attr), ))
+            # NOTE: multiprocessing cannot be covered by coverage
+            p = Process(target=run_gen_ncc_id, args=(attr, ))
             p.start()
             procs.append(p)
 
-        for p in procs:
-            p.join()
+        wait(procs, timeout=120)
 
     def test_flat(self):
         print(">>> test gen flat nccl id")