fix SGD lr check (#6244)

2 files changed, 7 insertions, 3 deletions

diff --git a/test/test_optim.py b/test/test_optim.py
index 386438960a..736d1b51b4 100644
--- a/test/test_optim.py
+++ b/test/test_optim.py
@@ -260,6 +260,10 @@ class TestOptim(TestCase):
                 self._build_params_dict_single(weight, bias, lr=1e-2),
                 lr=1e-3)
         )
+        self._test_basic_cases(
+            lambda weight, bias: optim.SGD(
+                self._build_params_dict_single(weight, bias, lr=1e-2))
+        )
         with self.assertRaisesRegex(ValueError, "Invalid momentum value: -0.5"):
             optim.SGD(None, lr=1e-2, momentum=-0.5)
 
diff --git a/torch/optim/sgd.py b/torch/optim/sgd.py
index f6d5a484ef..78cb3e189a 100644
--- a/torch/optim/sgd.py
+++ b/torch/optim/sgd.py
@@ -50,11 +50,11 @@ class SGD(Optimizer):
 
     def __init__(self, params, lr=required, momentum=0, dampening=0,
                  weight_decay=0, nesterov=False):
-        if not 0.0 <= lr:
+        if lr is not required and lr < 0.0:
             raise ValueError("Invalid learning rate: {}".format(lr))
-        if not 0.0 <= momentum:
+        if momentum < 0.0:
             raise ValueError("Invalid momentum value: {}".format(momentum))
-        if not 0.0 <= weight_decay:
+        if weight_decay < 0.0:
             raise ValueError("Invalid weight_decay value: {}".format(weight_decay))
 
         defaults = dict(lr=lr, momentum=momentum, dampening=dampening,