[CFE] Add mean absolute numbers to TTestResult; print mean from -> to in benchmarker

Change-Id: If935f5d9668cc1bd12ba3e2af7ae55f3bdea141f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/421182
Commit-Queue: Jens Johansen <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: jensjoha

pkg/front_end/test/simple_stats.dart

@@ -27,10 +27,10 @@ class SimpleTTestStat {
     if (confidence < diffMean.abs()) {
       double percentDiff = diffMean * 100 / bMean;
       double percentDiffConfidence = confidence * 100 / bMean;
-      return new TTestResult(
-          true, percentDiff, percentDiffConfidence, diffMean, confidence);
+      return new TTestResult(true, percentDiff, percentDiffConfidence, diffMean,
+          confidence, aMean, bMean);
     } else {
-      return new TTestResult(false, 0, 0, 0, 0);
+      return new TTestResult(false, 0, 0, 0, 0, 0, 0);
     }
   }
 
@@ -106,9 +106,11 @@ class TTestResult {
   final double percentDiffConfidence;
   final double diff;
   final double confidence;
+  final double aMean;
+  final double bMean;
 
   TTestResult(this.significant, this.percentDiff, this.percentDiffConfidence,
-      this.diff, this.confidence);
+      this.diff, this.confidence, this.aMean, this.bMean);
 
   @override
   String toString() {
@@ -145,4 +147,11 @@ class TTestResult {
         "+/- "
         "${_format(confidence, fractionDigits: fractionDigits)}";
   }
+
+  String? meanChangeStringIfSignificant({int fractionDigits = 2}) {
+    if (!significant) return null;
+    return "${_format(bMean, fractionDigits: fractionDigits)} "
+        "-> "
+        "${_format(aMean, fractionDigits: fractionDigits)}";
+  }
 }

pkg/front_end/tool/benchmarker.dart

@@ -182,7 +182,8 @@ bool _compare(List<Map<String, num>> from, List<Map<String, num>> to) {
     if (stats.significant) {
       somethingWasSignificant = true;
       print("$caption: ${stats.percentChangeIfSignificant(fractionDigits: 4)} "
-          "(${stats.valueChangeIfSignificant(fractionDigits: 2)})");
+          "(${stats.valueChangeIfSignificant(fractionDigits: 2)}) "
+          "(${stats.meanChangeStringIfSignificant(fractionDigits: 2)})");
     }
   }
   return somethingWasSignificant;