Add convert_function_with_cache in dygraph_to_static_func (#23190)

* add unittest test=develop

* add function cache test=develop

python/paddle/fluid/dygraph/dygraph_to_static/program_translator.py

@@ -29,7 +29,7 @@ from paddle.fluid.dygraph.dygraph_to_static.ast_transformer import DygraphToStat
 from paddle.fluid.dygraph.dygraph_to_static.utils import ast_to_source_code
 from paddle.fluid.framework import in_dygraph_mode
 
-__all__ = ['ProgramTranslator']
+__all__ = ['ProgramTranslator', 'convert_function_with_cache']
 
 
 class FunctionCache(object):
@@ -66,6 +66,19 @@ class FunctionCache(object):
             self._get_dedent_code_string(func), None) is not None
 
 
+_CACHE_LOCK = threading.Lock()
+_FUNCTION_CACHE = FunctionCache()
+
+
+def convert_function_with_cache(dygraph_func):
+    """
+    Transform function of dygraph into static function using the cache mechanism.
+    """
+    with _CACHE_LOCK:
+        static_func = _FUNCTION_CACHE.get_or_cache_func(dygraph_func)
+        return static_func
+
+
 def synchronized(func):
     func.__lock__ = threading.Lock()
 
@@ -273,7 +286,7 @@ class ProgramTranslator(object):
                 "The decorator 'dygraph_to_static_graph' doesn't work in dygraph mode."
                 " Please use it in static mode.")
             return dygraph_func
-        static_func, ast_transformer = convert_to_static(dygraph_func)
+        static_func = convert_function_with_cache(dygraph_func)
         return static_func
 
     def get_code(self, dygraph_func):

python/paddle/fluid/tests/unittests/dygraph_to_static/test_cache_program.py

@@ -21,7 +21,7 @@ from collections import Counter
 import paddle.fluid as fluid
 
 from paddle.fluid.dygraph.dygraph_to_static import ProgramTranslator
-from paddle.fluid.dygraph.jit import dygraph_to_static_output
+from paddle.fluid.dygraph.dygraph_to_static import convert_function_with_cache
 
 from test_fetch_feed import Pool2D, Linear
 
@@ -111,5 +111,19 @@ class TestCacheProgramWithOptimizer(unittest.TestCase):
                                                             static_loss))
 
 
+def simple_func(x):
+    inputs = fluid.dygraph.to_variable(x)
+    mean = fluid.layers.mean(inputs)
+    return mean
+
+
+class TestConvertWithCache(unittest.TestCase):
+    def test_cache(self):
+        static_func = convert_function_with_cache(simple_func)
+        # Get transformed function from cache.
+        cached_func = convert_function_with_cache(simple_func)
+        self.assertTrue(id(static_func), id(cached_func))
+
+
 if __name__ == '__main__':
     unittest.main()