use list for lr_mult

tensorpack/models/model_desc.py

@@ -65,6 +65,6 @@ class ModelDesc(object):
 
     def get_lr_multiplier(self):
         """
-        Return a dict of {variable_regex: multiplier}
+        Return a list of (variable_regex: multiplier)
         """
-        return {}
+        return []

tensorpack/train.py

@@ -86,7 +86,7 @@ def scale_grads(grads, multiplier):
     ret = []
     for grad, var in grads:
         varname = var.name
-        for regex, val in multiplier.iteritems():
+        for regex, val in multiplier:
             if re.search(regex, varname):
                 logger.info("Apply lr multiplier {} for {}".format(val, varname))
                 ret.append((grad * val, var))