Upgrade V8 to version 4.9.385.28
https://chromium.googlesource.com/v8/v8/+/4.9.385.28
FPIIM-449
Change-Id: I4b2e74289d4bf3667f2f3dc8aa2e541f63e26eb4
diff --git a/test/mjsunit/random-bit-correlations.js b/test/mjsunit/random-bit-correlations.js
new file mode 100644
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--- /dev/null
+++ b/test/mjsunit/random-bit-correlations.js
@@ -0,0 +1,69 @@
+// 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 --nostress-opt --noalways-opt --predictable
+
+(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;
+ }
+ }
+ }
+})();