From 00dda54f4f1f52ad497747a2316309cc2d0cbf05 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Date: Sun, 21 Jun 2020 17:12:18 -0400
Subject: [PATCH] ensure search window is increasing and greater than tolerance

---
 numerical_methods/golden_search_extrema.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/numerical_methods/golden_search_extrema.cpp b/numerical_methods/golden_search_extrema.cpp
index 5a327c1ef..5d84c5572 100644
--- a/numerical_methods/golden_search_extrema.cpp
+++ b/numerical_methods/golden_search_extrema.cpp
@@ -31,6 +31,14 @@ double get_minima(const std::function<double(double)> &f, double lim_a,
     double c, d;
     double prev_mean, mean = std::numeric_limits<double>::infinity();
 
+    // ensure that lim_a < lim_b
+    if (lim_a > lim_b) {
+        std::swap(lim_a, lim_b);
+    } else if (std::abs(lim_a - lim_b) <= EPSILON) {
+        std::cerr << "Search range must be greater than " << EPSILON << "\n";
+        return lim_a;
+    }
+
     do {
         prev_mean = mean;