add self.metric for ReduceLROnPlateau optimizer

Author: junyanz

models/base_model.py

@@ -41,6 +41,7 @@ def __init__(self, opt):
         self.visual_names = []
         self.optimizers = []
         self.image_paths = []
+        self.metric = 0 #  used for learning rate policy 'plateau'
 
     @staticmethod
     def modify_commandline_options(parser, is_train):
@@ -115,7 +116,7 @@ def get_image_paths(self):
     def update_learning_rate(self):
         """Update learning rates for all the networks; called at the end of every epoch"""
         for scheduler in self.schedulers:
-            scheduler.step()
+            scheduler.step(self.metric)
         lr = self.optimizers[0].param_groups[0]['lr']
         print('learning rate = %.7f' % lr)