Revert of Add test to check PRNG quality.

test/mjsunit/random-bit-correlations.js

-// Copyright 2015 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Flags: --random-seed=12
-
-(function() {
-  var kHistory = 2;
-  var kRepeats = 100;
-  var history = new Uint32Array(kHistory);
-
-  function random() {
-    return (Math.random() * Math.pow(2, 32)) >>> 0;
-  }
-
-  function ChiSquared(m, n) {
-    var ys_minus_np1 = (m - n / 2.0);
-    var chi_squared_1 = ys_minus_np1 * ys_minus_np1 * 2.0 / n;
-    var ys_minus_np2 = ((n - m) - n / 2.0);
-    var chi_squared_2 = ys_minus_np2 * ys_minus_np2 * 2.0 / n;
-    return chi_squared_1 + chi_squared_2;
-  }
-  for (var predictor_bit = -2; predictor_bit < 32; predictor_bit++) {
-    // The predicted bit is one of the bits from the PRNG.
-    for (var random_bit = 0; random_bit < 32; random_bit++) {
-      for (var ago = 0; ago < kHistory; ago++) {
-        // We don't want to check whether each bit predicts itself.
-        if (ago == 0 && predictor_bit == random_bit) continue;
-        // Enter the new random value into the history
-        for (var i = ago; i >= 0; i--) {
-          history[i] = random();
-        }
-        // Find out how many of the bits are the same as the prediction bit.
-        var m = 0;
-        for (var i = 0; i < kRepeats; i++) {
-          for (var j = ago - 1; j >= 0; j--) history[j + 1] = history[j];
-          history[0] = random();
-          var predicted;
-          if (predictor_bit >= 0) {
-            predicted = (history[ago] >> predictor_bit) & 1;
-          } else {
-            predicted = predictor_bit == -2 ? 0 : 1;
-          }
-          var bit = (history[0] >> random_bit) & 1;
-          if (bit == predicted) m++;
-        }
-        // Chi squared analysis for k = 2 (2, states: same/not-same) and one
-        // degree of freedom (k - 1).
-        var chi_squared = ChiSquared(m, kRepeats);
-        if (chi_squared > 24) {
-          var percent = Math.floor(m * 100.0 / kRepeats);
-          if (predictor_bit < 0) {
-            var bit_value = predictor_bit == -2 ? 0 : 1;
-            print(`Bit ${random_bit} is ${bit_value} ${percent}% of the time`);
-          } else {
-            print(`Bit ${random_bit} is the same as bit ${predictor_bit} ` +
-              `${ago} ago ${percent}% of the time`);
-          }
-        }
-        // For 1 degree of freedom this corresponds to 1 in a million.  We are
-        // running ~8000 tests, so that would be surprising.
-        assertTrue(chi_squared <= 24);
-        // If the predictor bit is a fixed 0 or 1 then it makes no sense to
-        // repeat the test with a different age.
-        if (predictor_bit < 0) break;
-      }
-    }
-  }
-})();