Ensure missing data points don’t lead to infinite loop

Missing data points can be represented as -1 values.
For the timeline, this would mean we end up in an infinite loop, because the value would be always become smaller instead of bigger as it would be expected.

This is avoided in two ways:
- extract method determineSignificantDigits(.,.), which ensures the input value is positive
- filter out negative numbers directly when collecting smallestValue

Signed-off-by: Stefan Marr <git@stefan-marr.de>

Author: smarr

codespeed/static/js/timeline.js

@@ -95,10 +95,20 @@ function getHighlighterConfig(median) {
   }
 }
 
+function determineSignificantDigits(value, digits) {
+  var val = Math.abs(value);
+
+  while (val < 1) {
+    val *= 10;
+    digits++;
+  }
+  return digits;
+}
+
 function renderPlot(data) {
   var plotdata = [],
       series = [],
-      lastvalues = [];//hopefully the smallest values for determining significant digits.
+      smallestValue = Number.MAX_SAFE_INTEGER; // hopefully the smallest values for determining significant digits.
   seriesindex = [];
   var hiddenSeries = 0;
   var median = data['data_type'] === 'M';
@@ -154,17 +164,17 @@ function renderPlot(data) {
       series.push(seriesConfig);
       seriesindex.push(exe_id);
       plotdata.push(data.branches[branch][exe_id]);
-      lastvalues.push(data.branches[branch][exe_id][0][1]);
-    }
-    //determine significant digits
-    var digits = 2;
-    var value = Math.min.apply( Math, lastvalues );
-    if (value !== 0) {
-      while( value < 1 ) {
-        value *= 10;
-        digits++;
+
+      // determine smallest non-negative value in lastvalues
+      // (missing values can be represented as -1)
+      var val = data.branches[branch][exe_id][0][1];
+      if (val > 0 && val < smallestValue) {
+        smallestValue = val;
       }
     }
+
+    var digits = determineSignificantDigits(smallestValue, 2);
+
     $("#plotgrid").html('<div id="plot"></div><div id="plotdescription"></div>');
 
     if (data.benchmark_description) {