Merge pull request #118 from dnouri/issues/optimizer-initialization

make sure model is initialized before optim init

skorch/net.py

@@ -916,6 +916,12 @@ def set_params(self, **kwargs):
             self.initialize_module()
             self.initialize_optimizer()
         if any(key.startswith('optimizer') for key in special_params):
+            # Model selectors such as GridSearchCV will set the
+            # parameters before .initialize() is called, therefore we
+            # need to make sure that we have an initialized model here
+            # as the optimizer depends on it.
+            if not hasattr(self, 'module_'):
+                self.initialize_module()
             self.initialize_optimizer()
 
         return self

skorch/tests/test_net.py

@@ -367,6 +367,12 @@ def test_changing_model_reinitializes_optimizer(self, net, data):
         # by the optimizer after 10 epochs.
         assert (abs(d2 - d1) > 1e-05).all()
 
+    def test_setting_optimizer_needs_model(self, net_cls, module_cls):
+        net = net_cls(module_cls)
+        assert not hasattr(net, 'module_')
+        # should not break
+        net.set_params(optimizer=torch.optim.SGD)
+
     def test_module_params_in_init(self, net_cls, module_cls, data):
         X, y = data