Fixes gpu tests failures in RocCurve by 2802 (#2867)

* Update roc_auc.py

* Fixed issues

Author: vfdev-5

ignite/contrib/metrics/roc_auc.py

@@ -18,8 +18,8 @@ def roc_auc_compute_fn(y_preds: torch.Tensor, y_targets: torch.Tensor) -> float:
 def roc_auc_curve_compute_fn(y_preds: torch.Tensor, y_targets: torch.Tensor) -> Tuple[Any, Any, Any]:
     from sklearn.metrics import roc_curve
 
-    y_true = y_targets.numpy()
-    y_pred = y_preds.numpy()
+    y_true = y_targets.cpu().numpy()
+    y_pred = y_preds.cpu().numpy()
     return roc_curve(y_true, y_pred)
 
 
@@ -181,9 +181,9 @@ def compute(self) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
         if idist.get_rank() == 0:
             # Run compute_fn on zero rank only
             fpr, tpr, thresholds = self.compute_fn(_prediction_tensor, _target_tensor)
-            fpr = torch.tensor(fpr)
-            tpr = torch.tensor(tpr)
-            thresholds = torch.tensor(thresholds)
+            fpr = torch.tensor(fpr, device=_prediction_tensor.device)
+            tpr = torch.tensor(tpr, device=_prediction_tensor.device)
+            thresholds = torch.tensor(thresholds, device=_prediction_tensor.device)
         else:
             fpr, tpr, thresholds = None, None, None
 

tests/ignite/contrib/metrics/test_roc_curve.py

@@ -149,7 +149,7 @@ def update(engine, i):
 
     engine = Engine(update)
 
-    device = "cpu" if idist.device().type == "xla" else idist.device()
+    device = torch.device("cpu") if idist.device().type == "xla" else idist.device()
     metric = RocCurve(device=device)
     metric.attach(engine, "roc_curve")
 
@@ -159,10 +159,14 @@ def update(engine, i):
 
     fpr, tpr, thresholds = engine.state.metrics["roc_curve"]
 
+    assert isinstance(fpr, torch.Tensor) and fpr.device == device
+    assert isinstance(tpr, torch.Tensor) and tpr.device == device
+    assert isinstance(thresholds, torch.Tensor) and thresholds.device == device
+
     y = idist.all_gather(y)
     y_pred = idist.all_gather(y_pred)
-    sk_fpr, sk_tpr, sk_thresholds = roc_curve(y, y_pred)
+    sk_fpr, sk_tpr, sk_thresholds = roc_curve(y.cpu().numpy(), y_pred.cpu().numpy())
 
-    assert np.array_equal(fpr, sk_fpr)
-    assert np.array_equal(tpr, sk_tpr)
-    np.testing.assert_array_almost_equal(thresholds, sk_thresholds)
+    np.testing.assert_array_almost_equal(fpr.cpu().numpy(), sk_fpr)
+    np.testing.assert_array_almost_equal(tpr.cpu().numpy(), sk_tpr)
+    np.testing.assert_array_almost_equal(thresholds.cpu().numpy(), sk_thresholds)