From b076067402160b4630ba722fe85be2787a445e43 Mon Sep 17 00:00:00 2001
From: Christoph Ruegg <git@cdrnet.ch>
Date: Sat, 8 Oct 2016 20:52:38 +0200
Subject: [PATCH] Root Finding: Zero Crossing Bracketing expansion must reset
 boundaries if it fails

---
 src/Numerics/RootFinding/ZeroCrossingBracketing.cs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Numerics/RootFinding/ZeroCrossingBracketing.cs b/src/Numerics/RootFinding/ZeroCrossingBracketing.cs
index 8af802e5..126df806 100644
--- a/src/Numerics/RootFinding/ZeroCrossingBracketing.cs
+++ b/src/Numerics/RootFinding/ZeroCrossingBracketing.cs
@@ -82,6 +82,9 @@ namespace MathNet.Numerics.RootFinding
         /// <remarks>This iterative methods stops when two values with opposite signs are found.</remarks>
         public static bool Expand(Func<double, double> f, ref double lowerBound, ref double upperBound, double factor = 1.6, int maxIterations = 50)
         {
+            double originalLowerBound = lowerBound;
+            double originalUpperBound = upperBound;
+
             if (lowerBound >= upperBound)
             {
                 throw new ArgumentOutOfRangeException("upperBound", string.Format(Resources.ArgumentOutOfRangeGreater, "xmax", "xmin"));
@@ -109,6 +112,8 @@ namespace MathNet.Numerics.RootFinding
                 }
             }
 
+            lowerBound = originalLowerBound;
+            upperBound = originalUpperBound;
             return false;
         }
     }