From c16297a59ed2ab9692e07d07d7ef82e3cdb6eb4b Mon Sep 17 00:00:00 2001
From: Kostyukov <cranky.ru@gmail.com>
Date: Fri, 2 Jun 2017 14:59:56 +0300
Subject: [PATCH] Bug was fixed in delta criterion

Delta criterion didn't work properly. Please, consider fix to add
---
 lib/lbfgs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/lbfgs.c b/lib/lbfgs.c
index 30ffcf2..c710cf3 100644
--- a/lib/lbfgs.c
+++ b/lib/lbfgs.c
@@ -510,7 +510,7 @@ int lbfgs(
         /*
             Test for stopping criterion.
             The criterion is given by the following formula:
-                (f(past_x) - f(x)) / f(x) < \delta
+                |(f(past_x) - f(x))| / f(x) < \delta
          */
         if (pf != NULL) {
             /* We don't test the stopping criterion while k < past. */
@@ -519,7 +519,7 @@ int lbfgs(
                 rate = (pf[k % param.past] - fx) / fx;
 
                 /* The stopping criterion. */
-                if (rate < param.delta) {
+                if (fabs(rate) < param.delta) {
                     ret = LBFGS_STOP;
                     break;
                 }