Fix prepare data

gns/train.py

@@ -413,24 +413,26 @@ def setup_tensorboard(cfg, metadata):
 
 
 def prepare_data(example, device_id):
-    """Prepare data for training or validation."""
-    position = example[0][0].to(device_id)
-    particle_type = example[0][1].to(device_id)
-
-    if len(example[0]) == 4:  # if data loader includes material_property
-        material_property = example[0][2].to(device_id)
-        n_particles_per_example = example[0][3].to(device_id)
-    elif len(example[0]) == 3:
-        material_property = None
-        n_particles_per_example = example[0][2].to(device_id)
+    features, labels = example
+
+    if len(features) == 4:  # If material property is present
+        position, particle_type, material_property, n_particles_per_example = features
     else:
-        raise ValueError("Unexpected number of elements in the data loader")
-
-    labels = example[1].to(device_id)
-
+        position, particle_type, n_particles_per_example = features
+        material_property = None
+
+    # Convert numpy arrays to tensors
+    position = torch.from_numpy(position).float().to(device_id)
+    particle_type = torch.from_numpy(particle_type).long().to(device_id)
+    if material_property is not None:
+        material_property = torch.from_numpy(np.array(material_property)).float().to(device_id)
+    n_particles_per_example = torch.tensor([n_particles_per_example], device=device_id).long()
+    labels = torch.from_numpy(labels).float().to(device_id)
+
     return position, particle_type, material_property, n_particles_per_example, labels
 
 
+
 def train(rank, cfg, world_size, device, verbose, use_dist):
     """Train the model.