add DISABLE_PLOT for test

python/paddle/v2/plot/plot_curve.py

@@ -1,5 +1,5 @@
-import matplotlib.pyplot as plt
 from IPython import display
+import os
 
 
 class PlotCost(object):
@@ -11,18 +11,29 @@ class PlotCost(object):
         self.train_costs = ([], [])
         self.test_costs = ([], [])
 
+        self.__disable_plot__ = os.environ.get("DISABLE_PLOT")
+        if not self.__plot_is_disabled__():
+            import matplotlib.pyplot as plt
+            self.plt = plt
+
+    def __plot_is_disabled__(self):
+        return self.__disable_plot__ == "True"
+
     def plot(self):
-        plt.plot(*self.train_costs)
-        plt.plot(*self.test_costs)
+        if self.__plot_is_disabled__():
+            return
+
+        self.plt.plot(*self.train_costs)
+        self.plt.plot(*self.test_costs)
         title = []
         if len(self.train_costs[0]) > 0:
             title.append('Train Cost')
         if len(self.test_costs[0]) > 0:
             title.append('Test Cost')
-        plt.legend(title, loc='upper left')
+        self.plt.legend(title, loc='upper left')
         display.clear_output(wait=True)
-        display.display(plt.gcf())
-        plt.gcf().clear()
+        display.display(self.plt.gcf())
+        self.plt.gcf().clear()
 
     def append_train_cost(self, step, cost):
         self.train_costs[0].append(step)