diff --git a/python/paddle/optimizer/lbfgs.py b/python/paddle/optimizer/lbfgs.py
index d309e67772b4cab7763e5123123c70ea430c1104..7afd59e65ade1873859be01401756a46331ea1de 100644
--- a/python/paddle/optimizer/lbfgs.py
+++ b/python/paddle/optimizer/lbfgs.py
@@ -143,6 +143,8 @@ def _strong_wolfe(
 
                 a_lo = aj;
         end(repeat)
+
+    reference: https://github.com/pytorch/pytorch
     """
 
     d_norm = d.abs().max()
@@ -275,7 +277,6 @@ def _strong_wolfe(
             # Armijo condition not satisfied or not lower than lowest point
             bracket[high_pos] = alpha
             bracket_f[high_pos] = loss_new
-            # bracket_g[high_pos] = grad_new.clone(memory_format=torch.contiguous_format)
             bracket_g[high_pos] = grad_new.clone()
             bracket_gtd[high_pos] = gtd_new
             low_pos, high_pos = (