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Add Randomizer::nextFloat() and Randomizer::getFloat() (#9679)

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* random: Add Randomizer::nextFloat()

* random: Check that doubles are IEEE-754 in Randomizer::nextFloat()

* random: Add Randomizer::nextFloat() tests

* random: Add Randomizer::getFloat() implementing the y-section algorithm

The algorithm is published in:

Drawing Random Floating-Point Numbers from an Interval. Frédéric
Goualard, ACM Trans. Model. Comput. Simul., 32:3, 2022.
https://doi.org/10.1145/3503512

* random: Implement getFloat_gamma() optimization

see https://github.com/php/php-src/pull/9679/files#r994668327

* random: Add Random\IntervalBoundary

* random: Split the implementation of γ-section into its own file

* random: Add tests for Randomizer::getFloat()

* random: Fix γ-section for 32-bit systems

* random: Replace check for __STDC_IEC_559__ by compile-time check for DBL_MANT_DIG

* random: Drop nextFloat_spacing.phpt

* random: Optimize Randomizer::getFloat() implementation

* random: Reject non-finite parameters in Randomizer::getFloat()

* random: Add NEWS/UPGRADING for Randomizer’s float functionality
This commit is contained in:
Tim Düsterhus 2022-12-14 17:48:47 +01:00 • committed by GitHub
parent 284f61ee22
commit f9a1a90380
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13 changed files with 511 additions and 6 deletions
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109
ext/random/randomizer.c
View file

@ -24,6 +24,7 @@
#include "ext/standard/php_array.h"
#include "ext/standard/php_string.h"
#include "Zend/zend_enum.h"
#include "Zend/zend_exceptions.h"
static inline void randomizer_common_init(php_random_randomizer *randomizer, zend_object *engine_object) {
@ -88,6 +89,114 @@ PHP_METHOD(Random_Randomizer, __construct)
}
/* }}} */
/* {{{ Generate a float in [0, 1) */
PHP_METHOD(Random_Randomizer, nextFloat)
{
php_random_randomizer *randomizer = Z_RANDOM_RANDOMIZER_P(ZEND_THIS);
uint64_t result;
size_t total_size;
ZEND_PARSE_PARAMETERS_NONE();
result = 0;
total_size = 0;
do {
uint64_t r = randomizer->algo->generate(randomizer->status);
result = result | (r << (total_size * 8));
total_size += randomizer->status->last_generated_size;
if (EG(exception)) {
RETURN_THROWS();
}
} while (total_size < sizeof(uint64_t));
/* A double has 53 bits of precision, thus we must not
* use the full 64 bits of the uint64_t, because we would
* introduce a bias / rounding error.
*/
#if DBL_MANT_DIG != 53
# error "Random_Randomizer::nextFloat(): Requires DBL_MANT_DIG == 53 to work."
#endif
const double step_size = 1.0 / (1ULL << 53);
/* Use the upper 53 bits, because some engine's lower bits
* are of lower quality.
*/
result = (result >> 11);
RETURN_DOUBLE(step_size * result);
}
/* }}} */
/* {{{ Generates a random float within a configurable interval.
*
* This method uses the γ-section algorithm by Frédéric Goualard.
*/
PHP_METHOD(Random_Randomizer, getFloat)
{
php_random_randomizer *randomizer = Z_RANDOM_RANDOMIZER_P(ZEND_THIS);
double min, max;
zend_object *bounds = NULL;
int bounds_type = 'C' + sizeof("ClosedOpen") - 1;
ZEND_PARSE_PARAMETERS_START(2, 3)
Z_PARAM_DOUBLE(min)
Z_PARAM_DOUBLE(max)
Z_PARAM_OPTIONAL
Z_PARAM_OBJ_OF_CLASS(bounds, random_ce_Random_IntervalBoundary);
ZEND_PARSE_PARAMETERS_END();
if (!zend_finite(min)) {
zend_argument_value_error(1, "must be finite");
RETURN_THROWS();
}
if (!zend_finite(max)) {
zend_argument_value_error(2, "must be finite");
RETURN_THROWS();
}
if (bounds) {
zval *case_name = zend_enum_fetch_case_name(bounds);
zend_string *bounds_name = Z_STR_P(case_name);
bounds_type = ZSTR_VAL(bounds_name)[0] + ZSTR_LEN(bounds_name);
}
switch (bounds_type) {
case 'C' + sizeof("ClosedOpen") - 1:
if (UNEXPECTED(max <= min)) {
zend_argument_value_error(2, "must be greater than argument #1 ($min)");
RETURN_THROWS();
}
RETURN_DOUBLE(php_random_gammasection_closed_open(randomizer->algo, randomizer->status, min, max));
case 'C' + sizeof("ClosedClosed") - 1:
if (UNEXPECTED(max < min)) {
zend_argument_value_error(2, "must be greater than or equal to argument #1 ($min)");
RETURN_THROWS();
}
RETURN_DOUBLE(php_random_gammasection_closed_closed(randomizer->algo, randomizer->status, min, max));
case 'O' + sizeof("OpenClosed") - 1:
if (UNEXPECTED(max <= min)) {
zend_argument_value_error(2, "must be greater than argument #1 ($min)");
RETURN_THROWS();
}
RETURN_DOUBLE(php_random_gammasection_open_closed(randomizer->algo, randomizer->status, min, max));
case 'O' + sizeof("OpenOpen") - 1:
if (UNEXPECTED(max <= min)) {
zend_argument_value_error(2, "must be greater than argument #1 ($min)");
RETURN_THROWS();
}
RETURN_DOUBLE(php_random_gammasection_open_open(randomizer->algo, randomizer->status, min, max));
default:
ZEND_UNREACHABLE();
}
}
/* }}} */
/* {{{ Generate positive random number */
PHP_METHOD(Random_Randomizer, nextInt)
{