Revert "ignore inf in loss tb summary, and report valid_rate"

This reverts commit 72cf8fa.

alf/algorithms/algorithm.py

@@ -1207,25 +1207,7 @@ def update_with_gradient(self,
             loss_info.loss * weight)
 
         loss_info = loss_info._replace(gns=gns)
-
-        new_fields_values = {}
-
-        def _mean_ignore_inf(path, loss):
-            inf_mask = torch.isinf(loss)
-            if inf_mask.any():
-                # populate the valid_rate field only when value can be inf.
-                new_fields_values[
-                    path + '-valid_rate'] = 1.0 - inf_mask.float().mean()
-            if inf_mask.all():
-                return torch.tensor(np.float32(np.inf), device=loss.device)
-            else:
-                return loss[~inf_mask].mean()
-
-        loss_info = alf.nest.py_map_structure_with_path(
-            _mean_ignore_inf, loss_info)
-
-        for k, v in new_fields_values.items():
-            loss_info = alf.nest.set_field(loss_info, k, v)
+        loss_info = alf.nest.map_structure(torch.mean, loss_info)
 
         return loss_info, all_params