Merge pull request #1712 from jacquesqiao/add-plot

add plot cost in v2 api

python/paddle/v2/plot/plot_curve.py

+from IPython import display
+import os
+
+
+class PlotCost(object):
+    """
+    append train and test cost in event_handle and then call plot.
+    """
+
+    def __init__(self):
+        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):
+        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')
+        self.plt.legend(title, loc='upper left')
+        display.clear_output(wait=True)
+        display.display(self.plt.gcf())
+        self.plt.gcf().clear()
+
+    def append_train_cost(self, step, cost):
+        self.train_costs[0].append(step)
+        self.train_costs[1].append(cost)
+
+    def append_test_cost(self, step, cost):
+        self.test_costs[0].append(step)
+        self.test_costs[1].append(cost)
+
+    def reset(self):
+        self.train_costs = ([], [])
+        self.test_costs = ([], [])