diff --git a/src/lib/lbfgs.c b/src/lib/lbfgs.c
index 93cc64e..277a847 100644
--- a/src/lib/lbfgs.c
+++ b/src/lib/lbfgs.c
@@ -651,8 +651,10 @@ int lbfgs(
             
             veccpy(d, dp, n);
         } else if (ys < yy) {
+            // 这里假设了初始的Hessian矩阵为单位阵乘以ys/yy
             vecscale(d, ys / yy, n); // 适当缩放d的大小
         } else {
+            // 假设初始的Hessian矩阵为 I + [(ys - yy)/tr(Yk)]diag(y2)
             veccpy(y2, lm[end].y, n);
             vecmul(y2, lm[end].y, n);
             vecdot(&Yk, y2, y2, n);
diff --git a/src/sample/sample4.cpp b/src/sample/sample4.cpp
index ad31406..9af17ee 100644
--- a/src/sample/sample4.cpp
+++ b/src/sample/sample4.cpp
@@ -187,7 +187,7 @@ int TEST_FUNC::Routine()
 	lbfgs_parameter_init(&self_para);
 	self_para.epsilon = 1e-7;
 
-	int ret = lbfgs(N, x, &fx, _Func, _Progress, this, &self_para, NULL);
+	int ret = lbfgs(N, x, &fx, _Func, _Progress, this, &self_para, _Precondition);
 
 	clog << endl << "L-BFGS optimization terminated with status: " << lbfgs_strerror(ret) << endl;
     clog << "Maximal difference = " << max_diff(x, m, N) << endl;