Correcting usage of Stopwatch TimeStamp Ticks vs DateTime Ticks

Author: LeeCampbell

README.md

@@ -20,7 +20,7 @@ namespace HdrHistogram.Examples
     /// </summary>
     static class SimpleHistogramExample
     {
-        private static readonly LongHistogram Histogram = new LongHistogram(TimeSpan.TicksPerHour, 3);
+        private static readonly LongHistogram Histogram = new LongHistogram(TimeStamp.Hours(1), 3);
         private static volatile Socket _socket;
         private static readonly Lazy<AddressFamily> AddressFamily = new Lazy<AddressFamily>(() => GetAddressFamily("google.com"));
 
@@ -57,20 +57,20 @@ private static void OutputMeasurements()
             var size = Histogram.GetEstimatedFootprintInBytes();
             Console.WriteLine("Histogram size = {0} bytes ({1:F2} MB)", size, size / 1024.0 / 1024.0);
 
-            Console.WriteLine("Recorded latencies [in ticks] for Create+Close of a DatagramSocket:");
+            Console.WriteLine("Recorded latencies [in system clock ticks] for Create+Close of a DatagramSocket:");
             Histogram.OutputPercentileDistribution(Console.Out, outputValueUnitScalingRatio: OutputScalingFactor.None);
             Console.WriteLine();
 
             Console.WriteLine("Recorded latencies [in usec] for Create+Close of a DatagramSocket:");
-            Histogram.OutputPercentileDistribution(Console.Out, outputValueUnitScalingRatio: OutputScalingFactor.TicksToMicroseconds);
+            Histogram.OutputPercentileDistribution(Console.Out, outputValueUnitScalingRatio: OutputScalingFactor.TimeStampToMicroseconds);
             Console.WriteLine();
 
             Console.WriteLine("Recorded latencies [in msec] for Create+Close of a DatagramSocket:");
-            Histogram.OutputPercentileDistribution(Console.Out, outputValueUnitScalingRatio: OutputScalingFactor.TicksToMilliseconds);
+            Histogram.OutputPercentileDistribution(Console.Out, outputValueUnitScalingRatio: OutputScalingFactor.TimeStampToMilliseconds);
             Console.WriteLine();
 
             Console.WriteLine("Recorded latencies [in sec] for Create+Close of a DatagramSocket:");
-            Histogram.OutputPercentileDistribution(Console.Out, outputValueUnitScalingRatio: OutputScalingFactor.TicksToSeconds);
+            Histogram.OutputPercentileDistribution(Console.Out, outputValueUnitScalingRatio: OutputScalingFactor.TimeStampToSeconds);
         }
 
         private static void CreateAndCloseDatagramSocket()

src/HdrHistogram.Examples/SimpleHistogramExample.cs

@@ -1,16 +1,18 @@
-using System;
-using System.Globalization;
+using System.Globalization;
 using System.IO;
 using NUnit.Framework;
 
 namespace HdrHistogram.UnitTests
 {
+    /// <summary>
+    /// Validates against files generated by the official Java implementation.
+    /// </summary>
     [TestFixture]
     public sealed class HgrmPercentileDistrubutionOutputTests
     {
         [Test, Combinatorial]
         public void PercentileDistrubution_hgrm_output_is_in_correct_format(
-            [Values(TimeSpan.TicksPerHour)]long highestTrackableValue,
+            [Values(36000000000)]long highestTrackableValue,
             [Values(1, 2, 3, 4, 5)]int signigicantDigits,
             [Values(10000.0)]double scaling,
             [Values(5, 10, 20)]int percentileTicksPerHalfDistance)
@@ -31,7 +33,7 @@ public void PercentileDistrubution_hgrm_output_is_in_correct_format(
 
         [Test, Combinatorial]
         public void PercentileDistrubution_csv_output_is_in_correct_format(
-            [Values(TimeSpan.TicksPerHour)]long highestTrackableValue,
+            [Values(36000000000)]long highestTrackableValue,
             [Values(1, 2, 3, 4, 5)]int signigicantDigits,
             [Values(10000.0)]double scaling,
             [Values(5, 10, 20)]int percentileTicksPerHalfDistance)

src/HdrHistogram.UnitTests/HgrmPercentileDistrubutionOutputTests.cs

@@ -5,7 +5,7 @@ namespace HdrHistogram.UnitTests
 {
     public abstract class HistogramTestBase
     {
-        private const long HighestTrackableValue = TimeSpan.TicksPerHour; // e.g. for 1 hr in ticks
+        private const long HighestTrackableValue = 7716549600;//TimeStamp.Hours(1); // e.g. for 1 hr in system clock ticks (StopWatch.Frequency)
         private const int NumberOfSignificantValueDigits = 3;
         private const long TestValueLevel = 4;
 

src/HdrHistogram.UnitTests/HistogramTestBase.cs

@@ -28,7 +28,7 @@ namespace HdrHistogram
     /// 36,000,000,000 while maintaining a value precision of 3 significant digits across that range.
     /// Value quantization within the range will thus be no larger than 1/1,000th (or 0.1%) of any value.
     /// This example Histogram could be used to track and analyze the counts of observed response times ranging between
-    /// 1 tick (100 nanoseconds) and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
+    /// 100 nanoseconds and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
     /// 100 microseconds, a resolution of 1 millisecond(or better) up to one second, and a resolution of 1 second 
     /// (or better) up to 1,000 seconds.
     /// At it's maximum tracked value(1 hour), it would still maintain a resolution of 3.6 seconds (or better).
@@ -122,8 +122,8 @@ public abstract class HistogramBase
         /// <remarks>
         /// Providing a lowestTrackableValue is useful in situations where the units used for the histogram's values are much 
         /// smaller that the minimal accuracy required.
-        /// For example when tracking time values stated in ticks (100 nanoseconds), where the minimal accuracy required is a
-        /// microsecond, the proper value for lowestTrackableValue would be 10.
+        /// For example when tracking time values stated in nanoseconds, where the minimal accuracy required is a
+        /// microsecond, the proper value for <paramref name="lowestTrackableValue"/> would be 1000.
         /// </remarks>
         protected HistogramBase(long lowestTrackableValue, long highestTrackableValue, int numberOfSignificantValueDigits)
         {

src/HdrHistogram/HistogramBase.cs

@@ -111,7 +111,7 @@ public static IEnumerable<HistogramIterationValue> Percentiles(this HistogramBas
         public static void OutputPercentileDistribution(this HistogramBase histogram,
             TextWriter writer,
             int percentileTicksPerHalfDistance = 5,
-            double outputValueUnitScalingRatio = OutputScalingFactor.TicksToMilliseconds,
+            double outputValueUnitScalingRatio = OutputScalingFactor.None,
             bool useCsvFormat = false)
         {
             var formatter = useCsvFormat
@@ -144,17 +144,22 @@ public static void OutputPercentileDistribution(this HistogramBase histogram,
 
         /// <summary>
         /// Executes the action and records the time to complete the action. 
-        /// The time is recorded in ticks. 
+        /// The time is recorded in system clock ticks. 
+        /// This time may vary between frameworks and platforms, but is equivalent to <c>(1/Stopwatch.Frequency)</c> seconds.
         /// Note this is a convenience method and can carry a cost.
         /// If the <paramref name="action"/> delegate is not cached, then it may incur an allocation cost for each invocation of <see cref="Record"/>
         /// </summary>
         /// <param name="histogram">The Histogram to record the latency in.</param>
         /// <param name="action">The functionality to execute and measure</param>
         /// <remarks>
         /// <para>
-        /// Ticks are used as the unit of recording here as they are the smallest unit that .NET can measure
-        /// and require no conversion at time of recording. Instead conversion (scaling) can be done at time
-        /// of output to microseconds, milliseconds, seconds or other appropriate unit.
+        /// The units returned from <code>Stopwatch.GetTimestamp()</code> are used as the unit of 
+        /// recording here as they are the smallest unit that .NET can measure and require no 
+        /// conversion at time of recording. 
+        /// Instead conversion (scaling) can be done at time of output to microseconds, milliseconds,
+        /// seconds or other appropriate unit.
+        /// These units are sometimes refered to as ticks, but should not not to be confused with 
+        /// ticks used in <seealso cref="DateTime"/> or <seealso cref="TimeSpan"/>.
         /// </para>
         /// <para>
         /// If you are able to cache the <paramref name="action"/> delegate, then doing so is encouraged.
@@ -187,9 +192,8 @@ public static void Record(this HistogramBase histogram, Action action)
         {
             var start = Stopwatch.GetTimestamp();
             action();
-            var elapsedTicks = (Stopwatch.GetTimestamp() - start);
-            histogram.RecordValue(elapsedTicks);
+            var elapsed = Stopwatch.GetTimestamp() - start;
+            histogram.RecordValue(elapsed);
         }
     }
-
 }

src/HdrHistogram/HistogramExtensions.cs

@@ -23,7 +23,7 @@ namespace HdrHistogram
     /// 36,000,000,000 while maintaining a value precision of 3 significant digits across that range.
     /// Value quantization within the range will thus be no larger than 1/1,000th (or 0.1%) of any value.
     /// This example Histogram could be used to track and analyze the counts of observed response times ranging between
-    /// 1 tick (100 nanoseconds) and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
+    /// 100 nanoseconds and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
     /// 100 microseconds, a resolution of 1 millisecond(or better) up to one second, and a resolution of 1 second 
     /// (or better) up to 1,000 seconds.
     /// At it's maximum tracked value(1 hour), it would still maintain a resolution of 3.6 seconds (or better).
@@ -52,7 +52,7 @@ public IntHistogram(long highestTrackableValue, int numberOfSignificantValueDigi
         /// <summary>
         /// Construct a <see cref="IntHistogram"/> given the lowest and highest values to be tracked and a number of significant decimal digits.
         /// Providing a <paramref name="lowestTrackableValue"/> is useful is situations where the units used for the histogram's values are much smaller that the minimal accuracy required.
-        /// For example when tracking time values stated in ticks (100 nanosecond units), where the minimal accuracy required is a microsecond, the proper value for <paramref name="lowestTrackableValue"/> would be 10.
+        /// For example when tracking time values stated in nanoseconds, where the minimal accuracy required is a microsecond, the proper value for <paramref name="lowestTrackableValue"/> would be 1000.
         /// </summary>
         /// <param name="lowestTrackableValue">
         /// The lowest value that can be tracked (distinguished from 0) by the histogram.

src/HdrHistogram/IntHistogram.cs

@@ -23,7 +23,7 @@ namespace HdrHistogram
     /// 36,000,000,000 while maintaining a value precision of 3 significant digits across that range.
     /// Value quantization within the range will thus be no larger than 1/1,000th (or 0.1%) of any value.
     /// This example Histogram could be used to track and analyze the counts of observed response times ranging between
-    /// 1 tick (100 nanoseconds) and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
+    /// 100 nanoseconds and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
     /// 100 microseconds, a resolution of 1 millisecond(or better) up to one second, and a resolution of 1 second 
     /// (or better) up to 1,000 seconds.
     /// At it's maximum tracked value(1 hour), it would still maintain a resolution of 3.6 seconds (or better).
@@ -51,7 +51,7 @@ public LongHistogram(long highestTrackableValue, int numberOfSignificantValueDig
         /// <summary>
         /// Construct a <see cref="LongHistogram"/> given the lowest and highest values to be tracked and a number of significant decimal digits.
         /// Providing a <paramref name="lowestTrackableValue"/> is useful is situations where the units used for the histogram's values are much smaller that the minimal accuracy required. 
-        /// For example when tracking time values stated in tick (100 nanosecond units), where the minimal accuracy required is a microsecond, the proper value for <paramref name="lowestTrackableValue"/> would be 10.
+        /// For example when tracking time values stated in nanosecond units, where the minimal accuracy required is a microsecond, the proper value for <paramref name="lowestTrackableValue"/> would be 1000.
         /// </summary>
         /// <param name="lowestTrackableValue">
         /// The lowest value that can be tracked (distinguished from 0) by the histogram.

src/HdrHistogram/LongHistogram.cs

@@ -6,7 +6,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/
  */
 
-using System;
+using System.Diagnostics;
 
 namespace HdrHistogram
 {
@@ -16,23 +16,40 @@ namespace HdrHistogram
     public static class OutputScalingFactor
     {
         /// <summary>
-        /// For use when values are recorded in ticks and output should be in ticks
+        /// For use when values are recorded and reported in the same unit of measurement.
         /// </summary>
         public const double None = 1.0;
-
+        
         /// <summary>
-        /// For use when values are recorded in ticks and output should be measured in microseconds.
+        /// For use when values are recorded with <seealso cref="Stopwatch.GetTimestamp()"/> and output should be reported in microseconds.
         /// </summary>
-        public const double TicksToMicroseconds = 10.0;
+        public static readonly double TimeStampToMicroseconds = Stopwatch.Frequency / (1000d * 1000d);
 
         /// <summary>
-        /// For use when values are recorded in ticks and output should be measured in milliseconds.
+        /// For use when values are recorded with <seealso cref="Stopwatch.GetTimestamp()"/> and output should be reported in milliseconds.
         /// </summary>
-        public const double TicksToMilliseconds = TimeSpan.TicksPerMillisecond;
+        public static readonly double TimeStampToMilliseconds = Stopwatch.Frequency / 1000d;
 
         /// <summary>
-        /// For use when values are recorded in ticks and output should be measured in seconds.
+        /// For use when values are recorded with <seealso cref="Stopwatch.GetTimestamp()"/> and output should be reported in seconds.
         /// </summary>
-        public const double TicksToSeconds = TimeSpan.TicksPerSecond;
+        public static readonly double TimeStampToSeconds = Stopwatch.Frequency;
+    }
+
+    public static class TimeStamp
+    {
+        public static long Seconds(int seconds)
+        {
+            return Stopwatch.Frequency*seconds;
+        }
+
+        public static long Minutes(int minutes)
+        {
+            return Stopwatch.Frequency * minutes * 60L;
+        }
+        public static long Hours(int hours)
+        {
+            return Stopwatch.Frequency * hours * 60L * 60L;
+        }
     }
 }

src/HdrHistogram/OutputScalingFactor.cs

@@ -24,7 +24,7 @@ namespace HdrHistogram
     /// 36,000,000,000 while maintaining a value precision of 3 significant digits across that range.
     /// Value quantization within the range will thus be no larger than 1/1,000th (or 0.1%) of any value.
     /// This example Histogram could be used to track and analyze the counts of observed response times ranging between
-    /// 1 tick (100 nanoseconds) and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
+    /// 100 nanoseconds and 1 hour in magnitude, while maintaining a value resolution of 100 nanosecond up to 
     /// 100 microseconds, a resolution of 1 millisecond(or better) up to one second, and a resolution of 1 second 
     /// (or better) up to 1,000 seconds.
     /// At it's maximum tracked value(1 hour), it would still maintain a resolution of 3.6 seconds (or better).
@@ -53,7 +53,7 @@ public ShortHistogram(long highestTrackableValue, int numberOfSignificantValueDi
         /// <summary>
         /// Construct a <see cref="ShortHistogram"/> given the lowest and highest values to be tracked and a number of significant decimal digits.
         /// Providing a <paramref name="lowestTrackableValue"/> is useful is situations where the units used for the histogram's values are much smaller that the minimal accuracy required. 
-        /// For example when tracking time values stated in ticks (100 nanosecond units), where the minimal accuracy required is a microsecond, the proper value for <paramref name="lowestTrackableValue"/> would be 10.
+        /// For example when tracking time values stated in nanoseconds, where the minimal accuracy required is a microsecond, the proper value for <paramref name="lowestTrackableValue"/> would be 1000.
         /// </summary>
         /// <param name="lowestTrackableValue">
         /// The lowest value that can be tracked (distinguished from 0) by the histogram.