diff --git a/lib/lbfgs.c b/lib/lbfgs.c
index c73f40c..db4e852 100644
--- a/lib/lbfgs.c
+++ b/lib/lbfgs.c
@@ -213,15 +213,6 @@ static void owlqn_project(
     const int end
     );
 
-static lbfgsfloatval_t owlqn_direction_line(
-    const lbfgsfloatval_t* x,
-    const lbfgsfloatval_t* g,
-    const lbfgsfloatval_t* s,
-    const lbfgsfloatval_t c,
-    const int start,
-    const int n
-    );
-
 
 #if     defined(USE_SSE) && (defined(__SSE__) || defined(__SSE2__))
 static int round_out_variables(int n)
@@ -342,17 +333,27 @@ int lbfgs(
     if (n < param.orthantwise_end) {
         return LBFGSERR_INVALID_ORTHANTWISE_END;
     }
-
-    switch (param.linesearch) {
-    case LBFGS_LINESEARCH_MORETHUENTE:
-        linesearch = line_search_morethuente;
-        break;
-    case LBFGS_LINESEARCH_BACKTRACKING:
-    case LBFGS_LINESEARCH_BACKTRACKING_STRONG:
-        linesearch = line_search_backtracking;
-        break;
-    default:
-        return LBFGSERR_INVALID_LINESEARCH;
+    if (param.orthantwise_c != 0.) {
+        switch (param.linesearch) {
+        case LBFGS_LINESEARCH_BACKTRACKING:
+            linesearch = line_search_backtracking_owlqn;
+            break;
+        default:
+            /* Only the backtracking method is available. */
+            return LBFGSERR_INVALID_LINESEARCH;
+        }
+    } else {
+        switch (param.linesearch) {
+        case LBFGS_LINESEARCH_MORETHUENTE:
+            linesearch = line_search_morethuente;
+            break;
+        case LBFGS_LINESEARCH_BACKTRACKING:
+        case LBFGS_LINESEARCH_BACKTRACKING_STRONG:
+            linesearch = line_search_backtracking;
+            break;
+        default:
+            return LBFGSERR_INVALID_LINESEARCH;
+        }
     }
 
     /* Allocate working space. */
@@ -803,12 +804,12 @@ static int line_search_morethuente(
     lbfgsfloatval_t *stp,
     const lbfgsfloatval_t* xp,
     const lbfgsfloatval_t* gp,
-    lbfgsfloatval_t *wp,
+    lbfgsfloatval_t *wa,
     callback_data_t *cd,
     const lbfgs_parameter_t *param
     )
 {
-    int i, count = 0;
+    int count = 0;
     int brackt, stage1, uinfo = 0;
     lbfgsfloatval_t dg;
     lbfgsfloatval_t stx, fx, dgx;
@@ -823,11 +824,6 @@ static int line_search_morethuente(
         return LBFGSERR_INVALIDPARAMETERS;
     }
 
-    /* Choose the orthant for the new point. */
-    for (i = 0;i < n;++i) {
-        wp[i] = (xp[i] == 0.) ? -gp[i] : xp[i];
-    }
-
     /* Compute the initial gradient in the search direction. */
     vecdot(&dginit, g, s, n);
 
@@ -889,14 +885,9 @@ static int line_search_morethuente(
         veccpy(x, xp, n);
         vecadd(x, s, *stp, n);
 
-        /* The current point is projected onto the orthant. */
-        owlqn_project(x, wp, param->orthantwise_start, param->orthantwise_end);
-
         /* Evaluate the function and gradient values. */
         *f = cd->proc_evaluate(cd->instance, x, g, cd->n, *stp);
-        *f += param->orthantwise_c * owlqn_x1norm(x, param->orthantwise_start, param->orthantwise_end);
-//        vecdot(&dg, g, s, n);
-        dg = owlqn_direction_line(x, g, s, param->orthantwise_c, param->orthantwise_start, param->orthantwise_end);
+        vecdot(&dg, g, s, n);
 
         ftest1 = finit + *stp * dgtest;
         ++count;
@@ -1364,47 +1355,3 @@ static void owlqn_project(
         }
     }
 }
-
-static lbfgsfloatval_t owlqn_direction_line(
-    const lbfgsfloatval_t* x,
-    const lbfgsfloatval_t* g,
-    const lbfgsfloatval_t* s,
-    const lbfgsfloatval_t c,
-    const int start,
-    const int n
-    )
-{
-    int i;
-    lbfgsfloatval_t d = 0.;
-
-    /* Compute the negative of gradients. */
-    for (i = 0;i < start;++i) {
-        d += s[i] * g[i];
-    }
-
-    /* Use psuedo-gradients for orthant-wise updates. */
-    for (i = start;i < n;++i) {
-        /* Notice that:
-            (-s[i] < 0)  <==>  (g[i] < -param->orthantwise_c)
-            (-s[i] > 0)  <==>  (param->orthantwise_c < g[i])
-           as the result of the lbfgs() function for orthant-wise updates.
-         */
-        if (s[i] != 0.) {
-            if (x[i] < 0.) {
-                /* Differentiable. */
-                d += s[i] * (g[i] - c);
-            } else if (0. < x[i]) {
-                /* Differentiable. */
-                d += s[i] * (g[i] + c);
-            } else if (s[i] < 0.) {
-                /* Take the left partial derivative. */
-                d += s[i] * (g[i] - c);
-            } else if (0. < s[i]) {
-                /* Take the right partial derivative. */
-                d += s[i] * (g[i] + c);
-            }
-        }
-    }
-
-    return d;
-}