fix NaNs in dt for zero-length intervals

torchode/step_size_controllers.py

@@ -478,7 +478,7 @@ def _select_initial_step(
             args,
         )
 
-        d2 = norm((f1 - f0) * inv_scale) / dt0
+        d2 = torch.where(dt0 == 0, torch.inf, norm((f1 - f0) * inv_scale) / dt0)
 
         maxd1d2 = torch.maximum(d1, d2)
         dt1 = torch.where(