Exporters.Plotting: ScottPlot histogram export

src/BenchmarkDotNet.Exporters.Plotting/ScottPlotExporter.cs

@@ -8,6 +8,7 @@
 using BenchmarkDotNet.Reports;
 using ScottPlot;
 using ScottPlot.Plottables;
+using ScottPlot.Statistics;
 
 namespace BenchmarkDotNet.Exporters.Plotting
 {
@@ -37,6 +38,7 @@ public ScottPlotExporter(int width = 1920, int height = 1080)
             this.Height = height;
             this.IncludeBarPlot = true;
             this.IncludeBoxPlot = true;
+            this.IncludeHistogramPlot = true;
             this.RotateLabels = true;
         }
 
@@ -78,6 +80,12 @@ public ScottPlotExporter(int width = 1920, int height = 1080)
         /// </summary>
         public bool IncludeBoxPlot { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether a histogram plot for time-per-op
+        /// measurement values should be exported.
+        /// </summary>
+        public bool IncludeHistogramPlot { get; set; }
+
         /// <summary>
         /// Not supported.
         /// </summary>
@@ -141,6 +149,18 @@ where measurement.Is(IterationMode.Workload, IterationStage.Result)
                         annotations);
                 }
 
+                if (this.IncludeHistogramPlot)
+                {
+                    // <BenchmarkName>-histogramplot.png
+                    yield return CreateHistogramPlot(
+                        $"{title} - {benchmarkName}",
+                        Path.Combine(summary.ResultsDirectoryPath, $"{title}-{benchmarkName}-histogramplot.png"),
+                        "Count",
+                        $"Time ({timeUnit})",
+                        timeStats,
+                        annotations);
+                }
+
                 /* TODO: Rest of the RPlotExporter plots.
                 <BenchmarkName>-<MethodName>-density.png
                 <BenchmarkName>-<MethodName>-facetTimeline.png
@@ -347,6 +367,60 @@ private string CreateBoxPlot(string title, string fileName, string yLabel, strin
             return Path.GetFullPath(fileName);
         }
 
+        // This doesn't support RotateTicks. I figure it's not necessary, since they're not category labels and thus shouldn't be very long
+        private string CreateHistogramPlot(string title, string fileName, string yLabel, string xLabel, IEnumerable<ChartStats> data, IReadOnlyList<Annotation> annotations)
+        {
+            Plot plt = new Plot();
+            plt.Title(title, this.TitleFontSize);
+            plt.YLabel(yLabel, this.FontSize);
+            plt.XLabel(xLabel, this.FontSize);
+
+            var palette = new ScottPlot.Palettes.Category10();
+
+            var legendPalette = data.Select(d => d.JobId)
+                .Distinct()
+                .Select((jobId, index) => (jobId, index))
+                .ToDictionary(t => t.jobId, t => palette.GetColor(t.index).WithAlpha(0.5));
+
+            plt.Legend.IsVisible = true;
+            plt.Legend.Alignment = Alignment.UpperRight;
+            plt.Legend.FontSize = this.FontSize;
+            var legend = data.Select(d => d.JobId)
+                .Distinct()
+                .Select((label, index) => new LegendItem()
+                {
+                    LabelText = label,
+                    FillColor = legendPalette[label]
+                })
+                .ToList();
+
+            plt.Legend.ManualItems.AddRange(legend);
+
+            var jobCount = plt.Legend.ManualItems.Count;
+
+            plt.Axes.Left.TickLabelStyle.FontSize = this.FontSize;
+            plt.Axes.Bottom.MajorTickStyle.Length = 0;
+            plt.Axes.Bottom.TickLabelStyle.FontSize = this.FontSize;
+
+            // 5 is an arbitrary multiplier, this may need to be responsive to the number of points
+            // There are theoretically optimzal binsizes (e.g. the 2 * IQR * N^(-1/3) rule), but they tend to make significant assumptions about the data
+            var binWidth = data.GroupBy(s => s.Target).SelectMany(tg => tg.Select(stats => 5 * (stats.Max - stats.Min) / stats.Values.Count)).Min();
+
+            foreach (var (targetGroup, targetGroupIndex) in data.GroupBy(s => s.Target).Select((targetGroup, index) => (targetGroup, index)))
+            {
+                var hists = targetGroup.Select((job) => (job, hist: Histogram.WithBinSize(binWidth, job.Values)));
+
+                foreach (var (job, hist) in hists) {
+                    plt.Add.Histogram(hist, legendPalette[job.JobId]);
+                }
+            }
+
+            plt.PlottableList.AddRange(annotations);
+
+            plt.SavePng(fileName, this.Width, this.Height);
+            return Path.GetFullPath(fileName);
+        }
+
         /// <summary>
         /// Provides a list of annotations to put over the data area.
         /// </summary>

tests/BenchmarkDotNet.Exporters.Plotting.Tests/ScottPlotExporterTests.cs

@@ -35,6 +35,7 @@ public void BarPlots(Type benchmarkType)
             {
                 IncludeBarPlot = true,
                 IncludeBoxPlot = false,
+                IncludeHistogramPlot = false,
             };
             var summary = MockFactory.CreateSummary(benchmarkType);
             var filePaths = exporter.ExportToFiles(summary, logger).ToList();
@@ -57,6 +58,7 @@ public void BoxPlots(Type benchmarkType)
             {
                 IncludeBarPlot = false,
                 IncludeBoxPlot = true,
+                IncludeHistogramPlot = false,
             };
             var summary = MockFactory.CreateSummaryWithBiasedDistribution(benchmarkType, 1, 4, 10, 9);
             var filePaths = exporter.ExportToFiles(summary, logger).ToList();
@@ -79,6 +81,7 @@ public void BoxPlotsWithOneMeasurement(Type benchmarkType)
             {
                 IncludeBarPlot = false,
                 IncludeBoxPlot = true,
+                IncludeHistogramPlot = false,
             };
             var summary = MockFactory.CreateSummaryWithBiasedDistribution(benchmarkType, 1, 4, 10, 1);
             var filePaths = exporter.ExportToFiles(summary, logger).ToList();
@@ -90,6 +93,29 @@ public void BoxPlotsWithOneMeasurement(Type benchmarkType)
             output.WriteLine(logger.GetLog());
         }
 
+        [Theory]
+        [MemberData(nameof(GetGroupBenchmarkTypes))]
+        public void HistogramPlots(Type benchmarkType)
+        {
+            var logger = new AccumulationLogger();
+            logger.WriteLine("=== " + benchmarkType.Name + " ===");
+
+            var exporter = new ScottPlotExporter()
+            {
+                IncludeBarPlot = false,
+                IncludeBoxPlot = false,
+                IncludeHistogramPlot = true,
+            };
+            var summary = MockFactory.CreateSummaryWithBiasedDistribution(benchmarkType, 1, 4, 10, 9);
+            var filePaths = exporter.ExportToFiles(summary, logger).ToList();
+            Assert.NotEmpty(filePaths);
+            Assert.All(filePaths, f => File.Exists(f));
+
+            foreach (string filePath in filePaths)
+                logger.WriteLine($"* {filePath}");
+            output.WriteLine(logger.GetLog());
+        }
+
         [SuppressMessage("ReSharper", "InconsistentNaming")]
         public static class BaselinesBenchmarks
         {