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442e0e8192
Change-Id: I34c317d3f11bef061cb9f2f6ad1123e948ef78f2 Reviewed-on: https://dart-review.googlesource.com/16683 Reviewed-by: Vyacheslav Egorov <vegorov@google.com> Reviewed-by: Kasper Lund <kasperl@google.com>
49 lines
1.4 KiB
Dart
49 lines
1.4 KiB
Dart
// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// Test that the distribution of hash codes for doubles is reasonable.
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// VMOptions=--intrinsify
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// VMOptions=--no_intrinsify
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import 'package:expect/expect.dart';
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main() {
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Expect.isTrue(ratio(0, 1) >= 0.95);
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Expect.isTrue(ratio(0, 100) >= 0.95);
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Expect.isTrue(ratio(0, 0xffffff) >= 0.95);
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Expect.isTrue(ratio(0xffffff) >= 0.95);
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Expect.isTrue(ratio(0xffffffff) >= 0.95);
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Expect.isTrue(ratio(0xffffffffffffff) >= 0.95);
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Expect.isTrue(ratio(0, -1) >= 0.95);
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Expect.isTrue(ratio(0, -100) >= 0.95);
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Expect.isTrue(ratio(0, -0xffffff) >= 0.95);
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Expect.isTrue(ratio(-0xffffff) >= 0.95);
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Expect.isTrue(ratio(-0xffffffff) >= 0.95);
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Expect.isTrue(ratio(-0xffffffffffffff) >= 0.95);
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}
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double ratio(num start, [num end]) {
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final n = 1000;
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end ??= (start + 1) * 2;
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// Collect the set of distinct doubles and the
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// set of distinct hash codes.
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final doubles = new Set<double>();
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final codes = new Set<int>();
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final step = (end.toDouble() - start.toDouble()) / n;
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var current = start.toDouble();
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for (int i = 0; i < n; i++) {
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doubles.add(current);
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codes.add(current.hashCode);
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current += step;
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}
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// Return the ratio between distinct doubles and
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// distinct hash codes.
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return codes.length / doubles.length;
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}
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