Adding description for Optimizers (#4371)

test/test_optim.py

@@ -67,6 +67,7 @@ def _test_rosenbrock_sparse(self, constructor, sparse_only=False):
 
         params = Variable(params_t, requires_grad=True)
         optimizer = constructor([params])
+
         if not sparse_only:
             params_c = Variable(params_t.clone(), requires_grad=True)
             optimizer_c = constructor([params_c])
@@ -113,6 +114,9 @@ def _test_basic_cases_template(self, weight, bias, input, constructor):
         input = Variable(input)
         optimizer = constructor(weight, bias)
 
+        # to check if the optimizer can be printed as a string
+        optimizer.__repr__()
+
         def fn():
             optimizer.zero_grad()
             y = weight.mv(input)
@@ -177,6 +181,7 @@ def fn_base(optimizer, weight, bias):
         state_dict = deepcopy(optimizer.state_dict())
         state_dict_c = deepcopy(optimizer.state_dict())
         optimizer_cuda.load_state_dict(state_dict_c)
+
         # Make sure state dict wasn't modified
         self.assertEqual(state_dict, state_dict_c)
 

torch/optim/optimizer.py

@@ -47,6 +47,17 @@ def __getstate__(self):
     def __setstate__(self, state):
         self.__dict__.update(state)
 
+    def __repr__(self):
+        format_string = self.__class__.__name__ + ' ('
+        for i, group in enumerate(self.param_groups):
+            format_string += '\n'
+            format_string += 'Parameter Group {0}\n'.format(i)
+            for key in sorted(group.keys()):
+                if key != 'params':
+                    format_string += '    {0}: {1}\n'.format(key, group[key])
+        format_string += ')'
+        return format_string
+
     def state_dict(self):
         """Returns the state of the optimizer as a :class:`dict`.