Fix to avoid RuntimeError (#2138)

Author: mseeger

litgpt/model.py

@@ -872,7 +872,7 @@ def build_rope_cache(
             theta = theta / factor
 
     # Create position indices `[0, 1, ..., seq_len - 1]`
-    seq_idx = torch.arange(seq_len, device=device) / condense_ratio
+    seq_idx = torch.arange(seq_len, device=device).float() / condense_ratio
 
     # Calculate the product of position index and $\theta_i$
     idx_theta = torch.outer(seq_idx, theta).repeat(1, 2)