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Tim Düsterhus
582b724c35
The reference implementation of the "Drawing Random Floating-Point Numbers from an Interval" paper contains two mistakes that will result in erroneous values being returned under certain circumstances: - For large values of `g` the multiplication of `k * g` might overflow to infinity. - The value of `ceilint()` might exceed 2^53, possibly leading to a rounding error when promoting `k` to double within the multiplication of `k * g`. This commit updates the implementation based on Prof. Goualard suggestions after reaching out to him. It will correctly handle inputs larger than 2^-1020 in absolute values. This limitation will be documented and those inputs possibly be rejected in a follow-up commit depending on performance concerns.
42 lines
803 B
PHP
42 lines
803 B
PHP
--TEST--
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Random: Randomizer: getFloat(): Extreme ranges are handled correctly
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--FILE--
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<?php
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use Random\Engine;
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use Random\Randomizer;
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final class TestEngine implements Engine
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{
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private array $values = [
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"\x64\xe8\x58\x79\x3e\xf6\x38\x00",
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"\x65\xe8\x58\x79\x3e\xf6\x38\x00",
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"\x00\x00\x00\x00\x00\x00\x00\x00",
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];
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public function generate(): string
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{
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return \array_shift($this->values);
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}
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}
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$r = new Randomizer(new TestEngine());
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$min = -1.6e308;
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$max = 1.6e308;
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printf("%.17g\n", $min);
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printf("%.17g\n\n", $max);
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printf("%.17g\n", $r->getFloat($min, $max));
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printf("%.17g\n", $r->getFloat($min, $max));
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printf("%.17g\n", $r->getFloat($min, $max));
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?>
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--EXPECT--
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-1.6e+308
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1.6e+308
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-1.5999999999999998e+308
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-1.6e+308
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1.5999999999999998e+308
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