[Perf] Display results with 4 significant figures (#3770)

- Fixes #3554

tools/perf-automation/Azure.Sdk.Tools.PerfAutomation.Tests/NumberFormatterTests.cs

@@ -0,0 +1,70 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using NUnit.Framework;
+using System;
+
+namespace Azure.Sdk.Tools.PerfAutomation.Tests
+{
+    public class NumberFormatterTests
+    {
+        // Standard Tests
+        [TestCase(0.00012345, 1, "0.0001")]
+        [TestCase(0.00012345, 2, "0.00012")]
+        [TestCase(0.00012345, 3, "0.000123")]
+        [TestCase(0.00012345, 4, "0.0001235")]
+        [TestCase(0.00012345, 5, "0.00012345")]
+        [TestCase(0.00012345, 6, "0.000123450")]
+        [TestCase(0.00012345, 7, "0.0001234500")]
+        [TestCase(1.2345, 1, "1")]
+        [TestCase(1.2345, 2, "1.2")]
+        [TestCase(1.2345, 3, "1.23")]
+        [TestCase(1.2345, 4, "1.235")]
+        [TestCase(1.2345, 5, "1.2345")]
+        [TestCase(1.2345, 6, "1.23450")]
+        [TestCase(1.2345, 7, "1.234500")]
+        [TestCase(12_345, 1, "12,345")]
+        [TestCase(12_345, 2, "12,345")]
+        [TestCase(12_345, 3, "12,345")]
+        [TestCase(12_345, 4, "12,345")]
+        [TestCase(12_345, 5, "12,345")]
+        [TestCase(12_345, 6, "12,345.0")]
+        [TestCase(12_345, 7, "12,345.00")]
+
+        // Group separator
+        [TestCase(12_345, 1, "12345", false)]
+        [TestCase(12_345, 2, "12345", false)]
+        [TestCase(12_345, 3, "12345", false)]
+        [TestCase(12_345, 4, "12345", false)]
+        [TestCase(12_345, 5, "12345", false)]
+        [TestCase(12_345, 6, "12345.0", false)]
+        [TestCase(12_345, 7, "12345.00", false)]
+
+        // Bug where fractional part of log10 was > 0.5
+        [TestCase(8.22929639076288, 4, "8.229")]
+
+        // Zero
+        [TestCase(0, 1, "0")]
+        [TestCase(0, 2, "0.0")]
+        [TestCase(0, 3, "0.00")]
+        [TestCase(0, 4, "0.000")]
+
+        // Negative numbers
+        [TestCase(-1, 1, "-1")]
+        [TestCase(-1, 4, "-1.000")]
+        [TestCase(-0.00012345, 4, "-0.0001235")]
+        [TestCase(-1.2345, 4, "-1.235")]
+        [TestCase(-12_345, 4, "-12,345")]
+        public void Format(double value, int minSignificantDigits, string expected, bool groupSeparator = true)
+        {
+            Assert.AreEqual(expected, NumberFormatter.Format(value, minSignificantDigits, groupSeparator));
+        }
+
+        [TestCase(1.2345, 0, typeof(ArgumentException))]
+        [TestCase(1.2345, -1, typeof(ArgumentException))]
+        public void FormatException(double value, int minSignificantDigits, Type expectedExceptionType)
+        {
+            Assert.Throws(expectedExceptionType, () => NumberFormatter.Format(value, minSignificantDigits));
+        }
+    }
+}

tools/perf-automation/Azure.Sdk.Tools.PerfAutomation/NumberFormatter.cs

@@ -0,0 +1,41 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+
+namespace Azure.Sdk.Tools.PerfAutomation
+{
+    public static class NumberFormatter
+    {
+        // Formats a number with a minimum number of significant digits.
+        // Digits to the left of the decimal point are always significant.
+        // Examples:
+        // - Format(0, 4) -> "0.000"
+        // - Format(12345, 4) -> "12,345"
+        // - Format(1.2345, 4) -> "1.235"
+        // - Format(0.00012345, 4) -> "0.0001235"
+        public static string Format(double value, int minSignificantDigits, bool groupSeparator = true)
+        {
+            if (minSignificantDigits <= 0)
+            {
+                throw new ArgumentException("Must be greater than zero", nameof(minSignificantDigits));
+            }
+
+            // Special case since log(0) is undefined
+            if (value == 0)
+            {
+                return value.ToString($"F{minSignificantDigits - 1}");
+            }
+
+            double log = Math.Log10(Math.Abs(value));
+            int significantDigits = (int)Math.Max(Math.Ceiling(log), minSignificantDigits);
+
+            double divisor = Math.Pow(10, Math.Ceiling(log) - significantDigits);
+            double rounded = divisor * Math.Round(value / divisor, MidpointRounding.AwayFromZero);
+
+            int decimals = (int)Math.Max(0, significantDigits - Math.Floor(log) - 1);
+
+            return rounded.ToString(groupSeparator ? $"N{decimals}" : $"F{decimals}");
+        }
+    }
+}

tools/perf-automation/Azure.Sdk.Tools.PerfAutomation/Program.cs

@@ -552,7 +552,8 @@ private static async Task WriteResultsSummaryThroughput(
                     row.Add(resultSummary.Test);
                     row.Add(resultSummary.Arguments);
 
-                    var operationsPerSecondStrings = operationsPerSecond(resultSummary).Select(o => $"{o.operationsPerSecond:F2}");
+                    var operationsPerSecondStrings = operationsPerSecond(resultSummary)
+                        .Select(o => $"{NumberFormatter.Format(o.operationsPerSecond, 4, groupSeparator: outputFormat != OutputFormat.Csv)}");
                     var operationsPerSecondDifferencesStrings = operationsPerSecondDifferences(resultSummary).Select(o => $"{o * 100:N2}%");
 
                     var values = operationsPerSecondStrings.Take(1).Concat(operationsPerSecondStrings.Skip(1)