Fix modules ignoring default device when created via native P/Invoke …

src/TorchSharp/NN/Module.cs

@@ -1138,10 +1138,8 @@ protected static (Device device, ScalarType dtype) GetDefaultDeviceAndType(Devic
                 internal T MoveModule<T>(Device? device, ScalarType? dtype) where T : Module
                 {
                     T module = (T)this;
-
-                    return device != null ?
-                       (dtype.HasValue ? (T)module._to(device, dtype.Value, false) : (T)module._to(device.type, device.index, false)) :
-                       (dtype.HasValue ? (T)module._to(dtype.Value, false) : module);
+                    var (targetDevice, targetDtype) = GetDefaultDeviceAndType(device, dtype);
+                    return (T)module._to(targetDevice, targetDtype, false);
                 }
 
                 protected void ClearModules() { _internal_submodules.clear(); }

test/TorchSharpTest/NN.cs

@@ -5264,6 +5264,37 @@ public void TestEmbeddingBagFromPretrained()
             }
         }
 
+        [Fact]
+        public void TestEmbeddingDefaultDevice()
+        {
+            // Regression test for https://github.com/dotnet/TorchSharp/issues/1438
+            // Embedding (and other native modules) ignored torch.set_default_device(),
+            // causing device mismatch when called with tensors on the default device.
+            var defaultDevice = torch.get_default_device();
+
+            try {
+                torch.set_default_device(torch.META);
+
+                // Before the fix, these modules were created on CPU despite META being
+                // the default device, which would cause "Expected all tensors to be on
+                // the same device" errors when used with tensors on the default device.
+                using (var emb = Embedding(2, 3)) {
+                    Assert.Equal(DeviceType.META, emb.weight!.device_type);
+                }
+
+                using (var emb = EmbeddingBag(2, 3)) {
+                    Assert.Equal(DeviceType.META, emb.weight!.device_type);
+                }
+
+                // Verify explicit device still takes precedence over default
+                using (var emb = Embedding(2, 3, device: torch.CPU)) {
+                    Assert.Equal(DeviceType.CPU, emb.weight!.device_type);
+                }
+            } finally {
+                torch.set_default_device(defaultDevice);
+            }
+        }
+
         [Fact]
         public void TestOneHotEncoding1()
         {