From 946ab8cec577b6a54fcf7e46f535b3dc66e284f8 Mon Sep 17 00:00:00 2001
From: mkzung <103102868+mkzung@users.noreply.github.com>
Date: Wed, 19 Aug 2026 18:52:28 +0500
Subject: [PATCH] Reject a ChoppinessIndex period of one

ComputeNextValue divides by Math.Log10(_period). At a period of one that
divisor is zero, so the double is infinite and the cast to decimal throws
OverflowException on the first update after warm-up. The constructor
accepts the value, so the failure lands on the data rather than on the
call that is wrong.

Beta, Correlation, Covariance and ValueAtRisk all reject a period their
formula cannot use, with the same message shape.
---
 Indicators/ChoppinessIndex.cs            |  9 +++++++--
 Tests/Indicators/ChoppinessIndexTests.cs | 10 ++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/Indicators/ChoppinessIndex.cs b/Indicators/ChoppinessIndex.cs
index b85b68affd4a..18c94199ed8d 100644
--- a/Indicators/ChoppinessIndex.cs
+++ b/Indicators/ChoppinessIndex.cs
@@ -46,10 +46,15 @@ public class ChoppinessIndex : BarIndicator, IIndicatorWarmUpPeriodProvider
         /// Creates a new ChoppinessIndex indicator using the specified period and moving average type
         /// </summary>
         /// <param name="name">The name of this indicator</param>
-        /// <param name="period">The period used for rolling windows for highs and lows</param>
+        /// <param name="period">The period used for rolling windows for highs and lows, must be greater than one</param>
         public ChoppinessIndex(string name, int period)
             : base(name)
         {
+            if (period < 2)
+            {
+                throw new ArgumentException($"Period parameter for ChoppinessIndex indicator must be greater than 1 but was {period}");
+            }
+
             _period = period;
 
             _trueRange = new TrueRange();
@@ -64,7 +69,7 @@ public ChoppinessIndex(string name, int period)
         /// <summary>
         /// Creates a new ChoppinessIndex indicator using the specified period
         /// </summary>
-        /// <param name="period">The period used for rolling windows for highs and lows</param>
+        /// <param name="period">The period used for rolling windows for highs and lows, must be greater than one</param>
         public ChoppinessIndex(int period)
             : this($"CHOP({period})", period)
         {
diff --git a/Tests/Indicators/ChoppinessIndexTests.cs b/Tests/Indicators/ChoppinessIndexTests.cs
index 48f20692606b..a3a07ad62591 100644
--- a/Tests/Indicators/ChoppinessIndexTests.cs
+++ b/Tests/Indicators/ChoppinessIndexTests.cs
@@ -13,6 +13,7 @@
  * limitations under the License.
 */
 
+using System;
 using NUnit.Framework;
 using QuantConnect.Data.Market;
 using QuantConnect.Indicators;
@@ -32,5 +33,14 @@ protected override IndicatorBase<IBaseDataBar> CreateIndicator()
         protected override string TestFileName => "spy_with_chop.csv";
 
         protected override string TestColumnName => "CHOP14";
+
+        [Test]
+        public void PeriodBelowMinimumThrows()
+        {
+            var period = 1;
+
+            var exception = Assert.Throws<ArgumentException>(() => new ChoppinessIndex(period));
+            Assert.That(exception.Message, Is.EqualTo($"Period parameter for ChoppinessIndex indicator must be greater than 1 but was {period}"));
+        }
     }
 }