force single thread when CINN is on (#44103)

python/paddle/fluid/compiler.py

@@ -16,6 +16,7 @@ import multiprocessing
 import os
 import six
 import sys
+import warnings
 from .. import compat as cpt
 from . import framework
 from .framework import _get_paddle_place, _get_paddle_place_list
@@ -373,6 +374,12 @@ class CompiledProgram(object):
             else:
                 self._exec_strategy.num_threads = len(places) * 2
 
+        if "FLAGS_use_cinn" in core.globals() and core.globals(
+        )["FLAGS_use_cinn"] and self._exec_strategy.num_threads != 1:
+            warnings.warn("At present, when CINN is turned on, each process can " \
+                  "only contain one thread, so reset the number of threads to 1 here.")
+            self._exec_strategy.num_threads = 1
+
         if self._build_strategy.num_trainers > 1:
             assert self._is_data_parallel, \
                 "If you use multi-trainer to train the model, you should use "\