lib: fix calculation of std and cv

RafaelGSS · Sep 18, 2024 · 157b675 · 157b675
1 parent f9449eb
commit 157b675
Showing 1 changed file with 9 additions and 6 deletions.
diff --git a/lib/histogram.js b/lib/histogram.js
@@ -112,11 +112,14 @@ class StatisticalHistogram {
   }
 
   calculateStd() {
-    const avgSquares = this.all.reduce(
-      (acc, value) => Math.min(Number.MAX_SAFE_INTEGER, Math.pow(value, 2) + acc), 0,
-    ) * (1 / this.all.length);
-
-    this.stddev = Math.sqrt(Math.max(0, this.all.length / (this.all.length - 1) * (avgSquares - (this.mean * this.mean))));
+    if (this.all.length < 2) {
+      this.stddev = 0;
+      return;
+    }
+    const variance = this.all.reduce((acc, value) => {
+      return acc + Math.pow(value - this.mean, 2);
+    }, 0) / (this.all.length - 1);
+    this.stddev = Math.sqrt(variance);
   }
 
   /**
@@ -125,7 +128,7 @@ class StatisticalHistogram {
    * - https://github.com/google/benchmark/blob/159eb2d0ffb85b86e00ec1f983d72e72009ec387/src/statistics.ccL81-L88
    */
   calculateCv() {
-    if (this.all.length < 2) {
+    if (this.all.length < 2 || this.mean === 0) {
       this.cv = 0;
       return;
     }