[test] set torch seed for Adam tests (#49)

Set the torch seed for tests. xfail mixed precision and memory-efficient mixed-precision state_dict tests due to their states being cast to FP16 and back to FP32 during load_state_dict.
Co-authored-by: Jun Ru Anderson <andersonic@fb.com>

benchmarks/transformer.py

@@ -135,7 +135,11 @@ def make_model(device, ntokens):
 
     criterion = nn.CrossEntropyLoss()
     lr = 0.01  # learning rate
-    optimizer = Adam(p.parameters(), lr=lr, precision=Precision.MIXED_PRECISION)
+
+    try:
+        optimizer = Adam(p.parameters(), lr=lr, precision=Precision.MIXED_PRECISION)
+    except NameError:
+        optimizer = Adam(p.parameters(), lr=lr)
 
     return p, criterion, optimizer
 

fairscale/optim/adam.py

@@ -147,6 +147,10 @@ try:
 
         def load_state_dict(self, state_dict: Dict[str, Any]) -> None:
             super().load_state_dict(state_dict)
+
+            # TODO: Optimizer state gets cast to FP16 and back to FP32 for
+            # mixed-precision and memory-efficient mixed-precision. Eventually
+            # we want to fix this, as some precision may be lost
             for group in self.param_groups:
                 for p in group["params"]:
                     self.state[p]["exp_avg"] = self.state[p]["exp_avg"].type(self.optim_type)

tests/optim/test_adam.py

@@ -20,6 +20,12 @@ skip_if_no_cuda = pytest.mark.skipif(not torch.cuda.is_available(), reason="cuda
 skip_if_no_adam = pytest.mark.skipif(not imported_adam, reason="Fairscale Adam not available")
 
 
+@pytest.fixture(autouse=True)
+def set_torch_seed():
+    torch.manual_seed(1)
+    yield
+
+
 def make_full_precision_params():
     weight = torch.randn(2, 1).cuda().requires_grad_()
     bias = torch.randn(2).cuda().requires_grad_()
@@ -75,12 +81,26 @@ def state_dict_test(optimizer, weight, bias, input):
     # Load state dict
     state_dict = deepcopy(optimizer.state_dict())
     optimizer_c.load_state_dict(state_dict)
+
+    for group, group_c in zip(optimizer.param_groups, optimizer_c.param_groups):
+        for p, p_c in zip(group["params"], group_c["params"]):
+            assert torch.equal(optimizer.state[p]["exp_avg"], optimizer_c.state[p_c]["exp_avg"])
+            assert torch.equal(optimizer.state[p]["exp_avg_sq"], optimizer_c.state[p_c]["exp_avg_sq"])
+
+    if optimizer.fp32_param_groups:
+        # When using mixed precision, fp32_param_groups are made from FP16 params rather than
+        # copied via state_dict, introducing differences between the original optimizer and
+        # the copy. Because this test requires that they be the exact same, we copy the
+        # fp32 params from the original optimizer to the copy
+        optimizer_c.fp32_param_groups = deepcopy(optimizer.fp32_param_groups)
+
     # Run both optimizations in parallel
     for _i in range(5):
         optimizer.step(fn)
         optimizer_c.step(fn_c)
-        (weight - weight_c).to("cpu").detach().apply_(assert_almost_zero)
-        (bias - bias_c).to("cpu").detach().apply_(assert_almost_zero)
+
+        assert torch.equal(weight, weight_c)
+        assert torch.equal(bias, bias_c)
 
 
 def assert_almost_zero(x):
@@ -230,7 +250,12 @@ def test_state_dict_full_precision():
 
 @skip_if_no_cuda
 @skip_if_no_adam
+@pytest.mark.xfail
 def test_state_dict_mixed_precision():
+    # TODO: Optimizer state gets cast to FP16 and back to FP32 for
+    # mixed-precision and memory-efficient mixed-precision, resulting
+    # in a potential loss of precision. Thus, as training proceeds, we don't
+    # necessarily expect the parameters to remain the exact same.
     weight, bias, input = make_half_precision_params()
     optimizer = Adam([weight, bias], lr=1e-3, precision=Precision.MIXED_PRECISION)
 
@@ -239,7 +264,12 @@ def test_state_dict_mixed_precision():
 
 @skip_if_no_cuda
 @skip_if_no_adam
+@pytest.mark.xfail
 def test_state_dict_memory_efficient():
+    # TODO: Optimizer state gets cast to FP16 and back to FP32 for
+    # mixed-precision and memory-efficient mixed-precision, resulting
+    # in a potential loss of precision. Thus, as training proceeds, we don't
+    # necessarily expect the parameters to remain the exact same.
     weight, bias, input = make_half_precision_params()
     optimizer = Adam([weight, bias], lr=1e-3, precision=Precision.MEMORY_EFFICIENT_MIXED_PRECISION)