[cherry-pick][jit] Jit skip forward (#45926)

* skip forward save

* fix bug

* more ci for jit skip forward

python/paddle/fluid/dygraph/jit.py

@@ -381,7 +381,8 @@ class _SaveLoadConfig(object):
 
 def _parse_save_configs(configs):
     supported_configs = [
-        'output_spec', "with_hook", "combine_params", "clip_extra"
+        'output_spec', "with_hook", "combine_params", "clip_extra",
+        "skip_forward"
     ]
 
     # input check
@@ -397,6 +398,7 @@ def _parse_save_configs(configs):
     inner_config.with_hook = configs.get('with_hook', False)
     inner_config.combine_params = configs.get("combine_params", False)
     inner_config.clip_extra = configs.get("clip_extra", False)
+    inner_config.skip_forward = configs.get("skip_forward", False)
 
     return inner_config
 
@@ -522,7 +524,10 @@ def _build_load_path_and_config(path, config):
             "don't know which one to load, please make sure that the specified target "
             "of ``path`` is unique." % (path, path))
     elif not prefix_format_exist and not directory_format_exist:
-        raise ValueError("The ``path`` (%s) to load model not exists." % path)
+        raise ValueError("The ``path`` (%s) to load model not exists. "
+                         "Please make sure that *.pdmodel exists or "
+                         "don't using ``skip_forward=True`` to jit.save." %
+                         path)
     else:
         if prefix_format_exist:
             file_prefix = os.path.basename(path)
@@ -906,6 +911,7 @@ def save(layer, path, input_spec=None, **configs):
 
     combine_vars = {}
     property_vals = []  # (value, key)
+    concrete_program = None
     for attr_func in functions:
         if isinstance(layer, Layer):
             static_func = getattr(inner_layer, attr_func, None)
@@ -921,6 +927,10 @@ def save(layer, path, input_spec=None, **configs):
                 concrete_program = static_func.concrete_program_specify_input_spec(
                     inner_input_spec, with_hook=with_hook)
             elif 'forward' == attr_func:
+                if configs.skip_forward:
+                    # do not jit.save forward function
+                    continue
+
                 # transform in jit.save, if input_spec is incomplete, declarative will throw error
                 # inner_input_spec is list[InputSpec], it should be packed with same structure
                 # as original input_spec here.
@@ -1100,10 +1110,10 @@ def save(layer, path, input_spec=None, **configs):
     # file `***.pdiparams.info`
 
     # "layer" can only be Layer or function or StaticFunction.
-
     contain_parameter = False
-    for var in concrete_program.main_program.list_vars():
-        contain_parameter |= isinstance(var, Parameter)
+    if concrete_program is not None:
+        for var in concrete_program.main_program.list_vars():
+            contain_parameter |= isinstance(var, Parameter)
 
     if (isinstance(layer, Layer) or contain_parameter) and extra_var_info:
         with scope_guard(scope):

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

@@ -1740,6 +1740,40 @@ class TestInputSpecCompatibility(unittest.TestCase):
             shutil.rmtree(save_dir)
 
 
+class NotJitForward(paddle.nn.Layer):
+
+    def __init__(self):
+        super(NotJitForward, self).__init__()
+
+    def forward(self, x, y):
+        return x + y
+
+
+class TestNotJitForward(unittest.TestCase):
+
+    def setUp(self):
+        self.temp_dir = tempfile.TemporaryDirectory()
+
+    def tearDown(self):
+        self.temp_dir.cleanup()
+
+    def test_jit_not_save_forward(self):
+        layer = NotJitForward()
+
+        save_dir = os.path.join(self.temp_dir.name, "jit_not_save_forward")
+        path = save_dir + "/model"
+
+        paddle.jit.save(layer=layer, path=path, skip_forward=True)
+
+        self.assertTrue(not os.path.exists(path + ".pdmodel"))
+        self.assertTrue(not os.path.exists(path + ".pdparam"))
+
+        with self.assertRaises(ValueError):
+            paddle.jit.load(path=path)
+
+        shutil.rmtree(save_dir)
+
+
 if __name__ == '__main__':
     with fluid.framework._test_eager_guard():
         unittest.main()