gistfile1.js

// To make the benchmark results predictable, we replace Math.random
// with a 100% deterministic alternative.
Math.random = (function() {
  var seed = 49734321;
  return function() {
    // Robert Jenkins' 32 bit integer hash function.
    seed = ((seed + 0x7ed55d16) + (seed << 12))  & 0xffffffff;
    seed = ((seed ^ 0xc761c23c) ^ (seed >>> 19)) & 0xffffffff;
    seed = ((seed + 0x165667b1) + (seed << 5))   & 0xffffffff;
    seed = ((seed + 0xd3a2646c) ^ (seed << 9))   & 0xffffffff;
    seed = ((seed + 0xfd7046c5) + (seed << 3))   & 0xffffffff;
    seed = ((seed ^ 0xb55a4f09) ^ (seed >>> 16)) & 0xffffffff;
    return (seed & 0xfffffff) / 0x10000000;
  };
})();

var table0 = mkTable(),
    table1 = mkTable(),
    table2 = mkTable(),
    table3 = mkTable();

function mkTable() {
  var N = Math.pow(2, 32);
  var t = new Int32Array(256);
  for (var i = 0; i < 256; i++) {
    var v = Math.random() * N;
    t[i] = v | 0;
  }
  return t;
}

function mkKey() {
  var key = new Uint8Array(20);
  for (var i = 0; i < 20; i++) key[i] = (Math.random() * 256) | 0;
  return key;
}

function hash(key) {
  var result = 0;
  for (var i = 0; i < 20; i += 4) {
    var a = key[i + 0];
    var b = key[i + 1];
    var c = key[i + 2];
    var d = key[i + 3];
    result = (result + a ^ table0[a]) | 0;
    result = (result + b ^ table1[b]) | 0;
    result = (result + c ^ table2[c]) | 0;
    result = (result + d ^ table3[d]) | 0;
  }
  return result;
}

var keys = new Array(100000);

for (var i = 0; i < keys.length; i++) {
  keys[i] = mkKey();
}

var start = Date.now();
for (var i = 0; i < keys.length; i++) {
  hash(keys[i]);
}
var end = Date.now();
print (end - start);