perf impact of reordering declaration ref list

calc.js

var master = [15.985, 15.774, 16.664, 16.111, 15.889, 15.603, 15.598, 15.690, 15.602, 16.159];

var reordered = [15.831, 16.182, 16.519, 15.383, 15.936, 15.888, 15.645, 15.775, 15.749, 16.076];

function mean(arr) {
  return arr.reduce(function(x,y) { return x + y; }) / arr.length;
}

function variance(arr) {
  var m = mean(arr);
  return mean(arr.map(function(x) {
    var diff = x - m;
    return diff*diff;
  }));
}

function stddev(arr) {
  return Math.sqrt(variance(arr));
}

function summarise(title, arr) {
  console.log(title + ":");
console.log("mean: " + mean(arr) + "s");
console.log("std dev: " + stddev(arr) + "s");
}

summarise("master", master);
summarise("reordered", reordered);

results.txt

*** current master ***

real    0m15.985s
user    1m24.916s
sys     0m26.712s

real    0m15.774s
user    1m25.188s
sys     0m25.840s

real    0m16.664s
user    1m29.352s
sys     0m27.292s

real    0m16.111s
user    1m25.568s
sys     0m27.128s

real    0m15.889s
user    1m25.332s
sys     0m26.176s

real    0m15.603s
user    1m23.188s
sys     0m26.628s

real    0m15.598s
user    1m22.132s
sys     0m27.304s

real    0m15.690s
user    1m23.196s
sys     0m26.740s

real    0m15.602s
user    1m24.196s
sys     0m25.564s

real    0m16.159s
user    1m25.284s
sys     0m27.264s

*** this branch ***

real    0m15.831s
user    1m24.448s
sys     0m26.440s

real    0m16.182s
user    1m25.628s
sys     0m27.200s

real    0m16.519s
user    1m26.384s
sys     0m28.056s

real    0m15.383s
user    1m21.764s
sys     0m26.812s

real    0m15.936s
user    1m25.824s
sys     0m25.820s

real    0m15.888s
user    1m25.448s
sys     0m25.952s

real    0m15.645s
user    1m23.276s
sys     0m26.700s

real    0m15.775s
user    1m24.872s
sys     0m25.908s

real    0m15.749s
user    1m25.428s
sys     0m25.632s

real    0m16.076s
user    1m24.292s
sys     0m27.124s

Output:

master:
mean: 15.907499999999999s
std dev: 0.3209788933870889s
reordered:
mean: 15.8984s
std dev: 0.29505531684753594s