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<?php declare(strict_types = 1);
/*
** Zabbix
** Copyright (C) 2001-2021 Zabbix SIA
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
**/
/**
* A math helper class.
*/
class CMathHelper {
/**
* Calculate sum of values (overflow safe).
*
* @param array $values
*
* @return float
*/
public static function safeSum(array $values): float {
sort($values, SORT_NUMERIC);
$result = $values[0];
$head = 1;
$tail = count($values) - 1;
while ($head <= $tail) {
$result += $values[$result > 0 ? $head++ : $tail--];
}
return $result;
}
/**
* Calculate multiplication of values (overflow safe).
*
* @param array $values
*
* @return float
*/
public static function safeMul(array $values): float {
usort($values, function(float $a, float $b): int {
return abs($a) <=> abs($b);
});
$result = $values[0];
$head = 1;
$tail = count($values) - 1;
while ($head <= $tail) {
$result *= $values[abs($result) > 1 ? $head++ : $tail--];
}
return $result;
}
/**
* Calculate average of values (overflow safe).
*
* @param array $values A non-empty array of values.
*
* @return float
*/
public static function safeAvg(array $values): float {
sort($values, SORT_NUMERIC);
$result = 0;
$count = 1;
$head = 0;
$tail = count($values) - 1;
while ($head <= $tail) {
$value = $values[$result > 0 ? $head++ : $tail--];
// Expression optimized to avoid overflow.
$result += $value / $count - $result / $count;
$count++;
}
return $result;
}
}
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