From: Michael Orlitzky <michael@orlitzky.com>
Date: Tue, 26 Mar 2013 00:43:55 +0000 (-0400)
Subject: Refix the non-negativity of denom in step_length_positive_definite().
X-Git-Url: https://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=602624313348cec0073320c36849e16aba12b4cf;p=octave.git

Refix the non-negativity of denom in step_length_positive_definite().
---

diff --git a/optimization/step_length_positive_definite.m b/optimization/step_length_positive_definite.m
index 7e15a46..b9fe48e 100644
--- a/optimization/step_length_positive_definite.m
+++ b/optimization/step_length_positive_definite.m
@@ -34,11 +34,12 @@ function alpha = step_length_positive_definite(g, Q, p)
   %
   denom = (p' * Q * p);
 
-  if (abs(denom) < eps)
+  % denom is non-negative, since it's a Q-norm. No need to abs() it.
+  if (denom < eps)
     % Catch divide-by-zeros. If denom is effectively zero, set it to
     % something tiny instead. This trick is also used in the PCGM.
-    denom = sign(denom)*eps;
+    denom = eps;
   end
 
-  alpha = -(g' * p)/denom;
+  alpha = (g' * g)/denom;
 end