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Unified Diff: test/mjsunit/random-bit-correlations.js

Issue 1472833004: Revert of Add test to check PRNG quality. (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: Created 5 years, 1 month ago
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Index: test/mjsunit/random-bit-correlations.js
diff --git a/test/mjsunit/random-bit-correlations.js b/test/mjsunit/random-bit-correlations.js
deleted file mode 100644
index 0561b544ba05d7abc02c70f1e593d77428aa598b..0000000000000000000000000000000000000000
--- a/test/mjsunit/random-bit-correlations.js
+++ /dev/null
@@ -1,69 +0,0 @@
-// 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;
- }
- }
- }
-})();
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