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<?php
final class Timer
{
private static ?Timer $instance = null;
private array $timers = [];
/**
* gets the instance via lazy initialization (created on first usage)
*/
public static function getInstance(): Timer
{
if (self::$instance === null) {
self::$instance = new self();
}
return self::$instance;
}
public function start_timer(string $timer_name, $instance): void
{
$this->timers[$timer_name][$instance]['start'] = microtime(true);
}
public function stop_timer(string $timer_name, $instance): void
{
if (isset($this->timers[$timer_name][$instance])) {
$this->timers[$timer_name][$instance]['end'] = microtime(true);
} else {
throw new InvalidArgumentException('Timer not found: ' . $timer_name);
}
}
public function get_time_deltas(): array
{
$deltas = [];
foreach ($this->timers as $timer_name => $timer) {
foreach ($timer as $instance) {
$delta = $this->compute_delta($instance);
if (is_float($delta)) {
$deltas[$timer_name][] = $delta * 1000;
}
}
}
$res = [];
foreach ($deltas as $timer_name => $data) {
$res[$timer_name]['avg'] = array_sum($data)/count($data);
$res[$timer_name]['std_dev'] = $this->standard_deviation($data);
$res[$timer_name]['data'] = $data;
}
return $res;
}
//src: https://www.geeksforgeeks.org/php-program-find-standard-deviation-array/
private function standard_deviation($array): float
{
$num_of_elements = count($array);
$variance = 0.0;
// calculating mean using array_sum() method
$average = array_sum($array)/$num_of_elements;
foreach($array as $i)
{
// sum of squares of differences between
// all numbers and means.
$variance += pow(($i - $average), 2);
}
return (float)sqrt($variance/$num_of_elements);
}
private function compute_delta($data)
{
if (isset($data['start']) && isset($data['end'])) {
return $data['end'] - $data['start'];
}
return false;
}
/**
* is not allowed to call from outside to prevent from creating multiple instances,
* to use the singleton, you have to obtain the instance from Singleton::getInstance() instead
*/
private function __construct()
{
}
/**
* prevent the instance from being cloned (which would create a second instance of it)
*/
private function __clone()
{
}
/**
* prevent from being unserialized (which would create a second instance of it)
*/
public function __wakeup()
{
throw new Exception("Cannot unserialize singleton");
}
}
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