add get_program_cache_key function

Author: jacquesqiao

python/paddle/fluid/executor.py

@@ -163,6 +163,22 @@ def fetch_var(name, scope=None, return_numpy=True):
     return tensor
 
 
+def get_program_cache_key(feed, fetch_list):
+    feed_var_names = feed.keys()
+
+    def to_name_str(var):
+        if isinstance(var, Variable):
+            return var.desc.name()
+        elif isinstance(var, str):
+            return var
+        else:
+            raise TypeError(str(var) + " should be Variable or str")
+
+    fetch_var_names = map(to_name_str, fetch_list)
+
+    return str(feed_var_names + fetch_var_names)
+
+
 class Executor(object):
     def __init__(self, places):
         if not isinstance(places, list) and not isinstance(places, tuple):
@@ -232,12 +248,13 @@ def run(self,
 
         Python executor takes a program, add feed operators and fetch operators to this program according
         to feed map and fetch_list. Feed map provides input data for the program. fetch_list provides
-        the variables that user want to get after program run. Note: the executor will run all
+        the variables(or names) that user want to get after program run. Note: the executor will run all
         operators in the program but not only the operators dependent by the fetch_list
 
         :param program: the program that need to run, if not provied, then default_main_program will be used.
         :param feed: feed variable map, e.g. {"image": ImageData, "label": LableData}
-        :param fetch_list: a list of variable that user want to get, run will return them according to this list.
+        :param fetch_list: a list of variable or variable names that user want to get, run will return them according
+        to this list.
         :param feed_var_name: the name for the input variable of feed Operator.
         :param fetch_var_name: the name for the output variable of feed Operator.
         :param scope: the scope used to run this program, you can switch it to different scope. default is global_scope
@@ -247,6 +264,8 @@ def run(self,
         """
         if feed is None:
             feed = {}
+        if not isinstance(feed, dict):
+            raise TypeError("feed should be a map")
         if fetch_list is None:
             fetch_list = []
 
@@ -260,10 +279,7 @@ def run(self,
             scope = global_scope()
 
         program_cache = None
-
-        feed_var_names = feed.keys()
-        fetch_var_names = [var.desc.name() for var in fetch_list]
-        program_cache_key = str(feed_var_names + fetch_var_names)
+        program_cache_key = get_program_cache_key(feed, fetch_list)
 
         if use_program_cache:
             # find program cache by cache_key

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

@@ -89,7 +89,7 @@ def check_decay(self, python_decay_fn, fluid_decay_fn, kwargs):
         exe.run(fluid.default_startup_program())
         for step in range(10):
             lr_val, = exe.run(fluid.default_main_program(),
-                              feed=[],
+                              feed={},
                               fetch_list=[decayed_lr])
             python_decayed_lr = python_decay_fn(
                 global_step=float(step), **kwargs)