update

python/paddle/v2/fluid/clip.py

@@ -112,58 +112,52 @@ class GradientClipByNorm(BaseGradientClipAttr):
 
 
 class GradientClipByGlobalNorm(BaseGradientClipAttr):
-    global_norm_var = None
-    local_norm_var = None
-    clip_norm_var = None
-    scale_var = None
-
-    @classmethod
-    def init(cls, clip_norm):
-        if not (isinstance(clip_norm, int) or isinstance(clip_norm, float)):
-            raise TypeError("The 'clip_norm' must be a value of int or float")
-
-        cls.global_norm_var = layers.fill_constant(
-            shape=[1], dtype="float32", value=0.0)
-        cls.local_norm_var = layers.create_tensor(dtype="float32")
-        cls.clip_norm_var = layers.fill_constant(
-            shape=[1], dtype="float32", value=clip_norm)
-
-    @classmethod
-    def check_init(cls):
-        if not (isinstance(cls.global_norm_var, framework.Variable) and
-                isinstance(cls.local_norm_var, framework.Variable) and
-                isinstance(cls.clip_norm_var, framework.Variable)):
-            raise ValueError(
-                "Class 'GradientClipByGlobalNorm' has not been properly initialized. \
-                 Please call GradientClipByGlobalNorm.init() first.")
+    def __init__(self, clip_norm, group_name="default_group"):
+        if not isinstance(group_name, basestring):
+            raise TypeError("'group_name' must be a basestring.")
+
+        self.clip_norm = clip_norm
+        self.group_name = group_name
 
     def process_context(self, context, param, grad):
-        cls = self.__class__
-        cls.check_init()
+        if self.group_name not in context:
+            context[self.group_name] = []
+            context[self.group_name + "_clip_value"] = self.clip_norm
+            context[self.group_name + "_clip"] = layers.fill_constant(
+                shape=[1], dtype="float32", value=self.clip_norm)
+        else:
+            if not self.clip_norm == context[self.group_name + "_clip_value"]:
+                raise ValueError(
+                    "All parameters' 'clip_norm' of a same group should be the same"
+                )
 
-        cls.local_norm_var = layers.reduce_sum(
-            input=layers.pow(x=grad, factor=2.0))
-        layers.sums(
-            input=[cls.local_norm_var, cls.global_norm_var],
-            out=[cls.global_norm_var])
+        local_norm_var = layers.reduce_sum(input=layers.pow(x=grad, factor=2.0))
+        context[self.group_name].append(local_norm_var)
 
-    def create_operators(self, param, grad):
-        cls = self.__class__
-        cls.check_init()
+        self.context = context
 
-        if cls.scale_var is None:
-            layers.sqrt(x=cls.global_norm_var, out=cls.global_norm_var)
-            cls.scale_var = layers.elementwise_div(
-                x=cls.clip_norm_var,
+    def create_operators(self, param, grad):
+        group_scale_name = self.group_name + "_scale"
+        if group_scale_name not in self.context:
+            group_norm_var = layers.sums(input=self.context[self.group_name])
+            layers.sqrt(x=group_norm_var, out=group_norm_var)
+            clip_var = self.context[self.group_name + "_clip"]
+            group_scale_var = layers.elementwise_div(
+                x=clip_var,
                 y=layers.elementwise_max(
-                    x=cls.clip_norm_var, y=cls.global_norm_var))
-            assert cls.scale_var.shape == (1L, )
+                    x=clip_var, y=group_norm_var))
+            assert group_scale_var.shape == (1L, )
+            self.context[group_scale_name] = group_scale_var
 
-        new_grad = layers.elementwise_mul(x=grad, y=cls.scale_var)
+        new_grad = layers.elementwise_mul(
+            x=grad, y=self.context[group_scale_name])
         return param, new_grad
 
 
-def gradient_clip_by_global_norm(clip_norm, param_list=None, program=None):
+def gradient_clip_by_global_norm(clip_norm,
+                                 param_list=None,
+                                 group_name="default_group",
+                                 program=None):
     if program is None:
         program = framework.default_main_program()
     if param_list is None:
@@ -175,9 +169,9 @@ def gradient_clip_by_global_norm(clip_norm, param_list=None, program=None):
             "'param_list' should be a list of Parameter or basestring(parameter's name)."
         )
 
-    GradientClipByGlobalNorm.init(clip_norm)
     for param in param_list:
-        param.gradient_clip_attr = GradientClipByGlobalNorm()
+        param.gradient_clip_attr = GradientClipByGlobalNorm(clip_norm,
+                                                            group_name)
 
 
 def append_gradient_clip_ops(param_grad):

python/paddle/v2/fluid/tests/test_gradient_clip.py

@@ -15,21 +15,10 @@ import numpy as np
 import paddle.v2 as paddle
 import paddle.v2.fluid as fluid
 
-
-def _get_global_param_norm_(params_grads):
-    res = fluid.layers.fill_constant(shape=[1], dtype="float32", value=0.0)
-    for _, grad in params_grads:
-        norm_var = fluid.layers.reduce_sum(
-            input=fluid.layers.pow(x=grad, factor=2.0))
-        fluid.layers.sums(input=[norm_var, res], out=[res])
-    fluid.layers.sqrt(x=res, out=res)
-    return res
-
-
 BATCH_SIZE = 128
-CLIP = 0.5
-prog = fluid.framework.Program()
+CLIP = 1
 
+prog = fluid.framework.Program()
 with fluid.program_guard(main_program=prog):
     image = fluid.layers.data(name='x', shape=[784], dtype='float32')
 
@@ -49,13 +38,12 @@ avg_cost_clip = prog_clip.block(0).var(avg_cost.name)
 p_g = fluid.backward.append_backward(loss=avg_cost)
 p_g_clip = fluid.backward.append_backward(loss=avg_cost_clip)
 
-with fluid.program_guard(main_program=prog):
-    gloabl_norm = _get_global_param_norm_(p_g)
-
 with fluid.program_guard(main_program=prog_clip):
     fluid.clip.gradient_clip_by_global_norm(clip_norm=CLIP)
     p_g_clip = fluid.clip.append_gradient_clip_ops(p_g_clip)
-    gloabl_norm_clip = _get_global_param_norm_(p_g_clip)
+
+grad_list = [elem[1] for elem in p_g]
+grad_clip_list = [elem[1] for elem in p_g_clip]
 
 train_reader = paddle.batch(
     paddle.reader.shuffle(
@@ -72,11 +60,21 @@ for data in train_reader():
     count += 1
     if count > 5:
         break
-    out, = exe.run(prog, feed=feeder.feed(data), fetch_list=[gloabl_norm])
-    out_clip, = exe.run(prog_clip,
-                        feed=feeder.feed(data),
-                        fetch_list=[gloabl_norm_clip])
-
-    if not np.allclose(out_clip, np.minimum(out, np.array([CLIP]))):
+    out = exe.run(prog, feed=feeder.feed(data), fetch_list=grad_list)
+    out_clip = exe.run(prog_clip,
+                       feed=feeder.feed(data),
+                       fetch_list=grad_clip_list)
+    global_norm = 0
+    for v in out[1:]:
+        global_norm += np.sum(np.power(v, 2))
+    global_norm = np.sqrt(global_norm)
+
+    global_norm_clip = 0
+    for v in out_clip[1:]:
+        global_norm_clip += np.sum(np.power(v, 2))
+    global_norm_clip = np.sqrt(global_norm_clip)
+
+    if not np.isclose(
+            a=global_norm_clip, b=np.minimum(global_norm, CLIP), rtol=5e-3):
         exit(1)
 exit(0)