php/archived-php-src
1
0
Fork 0
mirror of https://github.com/php/php-src.git synced 2026-03-24 00:02:20 +01:00
Code Issues Packages Projects Releases Wiki Activity

round: Abolished the CPU rounding mode change and modified it to a different logic. (#13435)

Browse Source 
* Removed changing CPU round mode and added processing to detect and correct errors.
This commit is contained in:
Saki Takamachi
2024-03-09 08:51:37 +09:00
committed by GitHub
parent 447e6428d5
commit 2e50371a7a
1 changed files with 19 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
ext/standard/math.c
View File

@@ -27,7 +27,6 @@
#include <float.h>
#include <math.h>
#include <stdlib.h>
#include <fenv.h>
#include "basic_functions.h"
@@ -163,9 +162,7 @@ static inline double php_round_helper(double integral, double value, double expo
* mode. For the specifics of the algorithm, see http://wiki.php.net/rfc/rounding
*/
PHPAPI double _php_math_round(double value, int places, int mode) {
double exponent;
double tmp_value;
int cpu_round_mode;
double exponent, tmp_value, tmp_value2;
if (!zend_finite(value) || value == 0.0) {
return value;
@@ -182,21 +179,29 @@ PHPAPI double _php_math_round(double value, int places, int mode) {
* 0.285 * 10000000000 => 2849999999.9999995
* floor(0.285 * 10000000000) => 2849999999
*
* Therefore, change the CPU rounding mode to away from 0 only from
* fegetround to fesetround.
* Add 1 to the absolute value of the value adjusted by floor or ceil, use the
* exponent to return it to its original precision, and compare it with value.
* If it is equal to value, it is assumed that the absolute value is 1 smaller
* due to error and will be corrected.
* e.g.
* 0.285 * 10000000000 => 2850000000.0
* floor(0.285 * 10000000000) => 2850000000
* 0.285 * 10000000000 => 2849999999.9999995
* floor(0.285 * 10000000000) => 2849999999 (tmp_value)
* tmp_value2 = 2849999999 + 1 => 2850000000
* 2850000000 / 10000000000 == 0.285 => true
* tmp_value = tmp_value2
*/
cpu_round_mode = fegetround();
if (value >= 0.0) {
fesetround(FE_UPWARD);
tmp_value = floor(places > 0 ? value * exponent : value / exponent);
tmp_value = floor(places > 0 ? value * exponent : value / exponent);
tmp_value2 = tmp_value + 1.0;
} else {
fesetround(FE_DOWNWARD);
tmp_value = ceil(places > 0 ? value * exponent : value / exponent);
tmp_value = ceil(places > 0 ? value * exponent : value / exponent);
tmp_value2 = tmp_value - 1.0;
}
if ((places > 0 ? tmp_value2 / exponent : tmp_value2 * exponent) == value) {
tmp_value = tmp_value2;
}
fesetround(cpu_round_mode);
/* This value is beyond our precision, so rounding it is pointless */
if (fabs(tmp_value) >= 1e16) {