eval arithmetic expression as a string vs calling function - performance

I was going to advice some fellow Perl developers against eval-ing formulas as a string each time the formula is calculated, and instead eval - once - functions for each formula. Thus, instead of calling eval thousands of times, a function is called. I.e:
Instead of:
sub calc_formulas_naive
{
my %formulas;
$formulas{formula_a} = '$ref->{metric_a} + $ref->{metric_b} * $ref->{metric_c} - 100 * $ref->{metric_c} / 1000 + 33.33 * $ref->{metric_d}';
$formulas{formula_b} = '$ref->{metric_a} * $ref->{metric_c} - 33';
$formulas{formula_c} = '$ref->{metric_a} * $ref->{metric_c} - 33 + 0.265 * ($ref->{metric_d} / $ref->{metric_c}) - $ref->{metric_a} + $ref->{metric_e} * ($ref->{metric_d} + 1)';
my $ref = shift #_;
my $form_a_val = eval $formulas{formula_a};
my $form_b_val = eval $formulas{formula_b};
my $form_c_val = eval $formulas{formula_c};
}
Use:
my %formulas_adv;
sub prep_formulas_adv # called only once prior to parsing!
{
my $sub = 'sub { my $ref = shift #_; my $result = $ref->{metric_a} + $ref->{metric_b} * $ref->{metric_c} - 100 * $ref->{metric_c} / 1000 + 33.33 * $ref->{metric_d}; return $result; }';
$formulas_adv{formula_a} = eval $sub;
$sub = 'sub { my $ref = shift #_; my $result = $ref->{metric_a} * $ref->{metric_c} - 33; return $result; }';
$formulas_adv{formula_b} = eval $sub;
$sub = 'sub { my $ref = shift #_; my $result = $ref->{metric_a} * $ref->{metric_c} - 33 + 0.265 * ($ref->{metric_d} / $ref->{metric_c}) - $ref->{metric_a} + $ref->{metric_e} * ($ref->{metric_d} + 1); return $result; }';
$formulas_adv{formula_c} = eval $sub;
}
sub calc_formulas_advanced
{
my $ref = shift #_;
my $form_a_val = $formulas_adv{formula_a}($ref);
my $form_b_val = $formulas_adv{formula_b}($ref);
my $form_c_val = $formulas_adv{formula_c}($ref);
}
Now the question itself. I was totally sure that 2nd approach gives noticeable advantage when processing big amounts of data. I haven't had access to my old projects, but I also was quite sure I saw the 2nd approach working faster than the 1st. After all, Perl doesn't have to compile anything on-the-run in this case.
But before giving the advice, I wrote a small artificial example with 5K text files populated with rand generated metrics, ran both implementations, and... I don't observe any advantage of using unnamed functions over strings evaluation.
What's the matter? Was I hallucinating all the time, when I thought that eval is less effective than a function?

Related

Calculate the time difference of two rows in laravel

I want calculate time different between 2 row and calculate rank.
this is my code:
public function testtima($sid,$rid){
$calcs=users::where([['si',$sid]])->first();
$calcr=users::where([['ri',$rid]])->first();
$stime=$calcs['created_at'];
$rtime=$calcr['created_at'];
$show['stime']=$stime;
$show['rtime']=$rtime;
$show['now']=carbon::now();
return $show;
}
how can i calculate $rtime-$stime ?
Use Carbon's method, diffInSeconds, diffInDays or diffInMonths etc:
public function testtima($sid,$rid){
$stime = users::where('si',$sid)->first()->created_at;
$rtime = users::where('ri',$rid)->first()->created_at;
$diff = (new Carbon($stime))->diffInSeconds($rtime);
//$diff = (new Carbon($stime))->diffInDays($rtime);
return $diff;
}
$row1= "2007-03-24";
$row2= "2009-06-26";
$diff = abs(strtotime($row2) - strtotime($row1));
$years = floor($diff / (365*60*60*24));
$months = floor(($diff - $years * 365*60*60*24) / (30*60*60*24));
$days = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24)/ (60*60*24));
printf("%d years, %d months, %d days\n", $years, $months, $days);

Doctrine distances function

I try to use a function which calculate distance between $user lat/lng and coordinates in my BDD with limited distance.
It's an SQL request and I try to use Doctrine to implement it.
Here is my code
$config = new \Doctrine\ORM\Configuration();
$config->addCustomNumericFunction('COS', 'DoctrineExtensions\Query\Mysql\Cos');
$config->addCustomNumericFunction('ACOS', 'DoctrineExtensions\Query\Mysql\Acos');
$config->addCustomNumericFunction('RADIANS', 'DoctrineExtensions\Query\Mysql\Radians');
$config->addCustomNumericFunction('SIN', 'DoctrineExtensions\Query\Mysql\Sin');
$maxLat = $form_citylat + rad2deg($rad / $R);
$minLat = $form_citylat - rad2deg($rad / $R);
$maxLng = $form_citylng + rad2deg(asin($rad / $R) / cos(deg2rad($form_citylat)));
$minLng = $form_citylng - rad2deg(asin($rad / $R) / cos(deg2rad($form_citylat)));
$qb = $this->createQueryBuilder('u')->select('u.lat, u.lng')
->addSelect('acos(sin(:lat)*sin(radians(u.Lat)) + cos(:lat)*cos(radians(u.Lat))*cos(radians(u.lng)-:lng)) * :R As D')
->where('lat Between :minlat And :maxlat And lng Between :minlng And :maxlng And acos(sin(:lat)*sin(radians(u.Lat)) + cos(:lat)*cos(radians(u.Lat))*cos(radians(u.Lng)-:lng)) * :R < :rad')
->setParameter('lat',deg2rad($form_citylat))
->setParameter('lng',deg2rad($form_citylng))
->setParameter('minlat',$minLat)
->setParameter('minlng',$minLng)
->setParameter('maxlat',$maxLat)
->setParameter('maxlng',$maxLng)
->setParameter('rad',$rad)
->setParameter('R',$R)
->orderBy('D');
return $qb->getQuery()->getResult();`
But I got this error message :
[Syntax Error] line 0, col 40: Error: Expected
Doctrine\ORM\Query\Lexer::T_CLOSE_PARENTHESIS, got '.'
I tried different options but it doesn't work.
Anyone has an answer please ?
public function findByThemeAndDistance($theme,$distance,$user){
$latUser=$user->getAddress()->getLnt();
$lngUser = $user->getAddress()->getLgt();
return $this->createQueryBuilder('a')
//->select('a as activity,dist('.$distance.') as distance' )
->join('a.author','u')
->join('u.address','add')
->andWhere('a.theme=:val')
->andWhere( '(6378 * acos(cos(radians( add.lnt)) * cos(radians(' . $latUser . ')) * cos(radians(' . $lngUser . ') - radians(add.lgt)) + sin(radians(add.lnt )) * sin(radians(' . $latUser . '))))< :distance')
->setParameter('distance', $distance)
->setParameter('val',$theme)
->orderBy( 'a.author','ASC')
->getQuery()
->getResult();
}

Php Generate random number without repeat

$C = $_POST['Cc'];
$X = $_POST['X'];
$CX = $_POST['Cc'] . $_POST['X'];
$NC = preg_replace_callback("/x/" ,function() {return rand(0,9);}, $CX);
$New = $NC ;
$NNew = str_repeat($New,10);
echo $NNew;
what's wrong when i output it , it gives me the same number How to make It Don't Give me the same Numbers ??
It's basically you are not changing the seed for the rand method. Each time it's getting same seed and generating same number.
Read this PHP manual : http://php.net/manual/en/function.srand.php
Check the code snippet below:
<?php
// seed with microseconds
function make_seed()
{
list($usec, $sec) = explode(' ', microtime());
return $sec + $usec * 1000000;
}
srand(make_seed());
$randval = rand(0,9);
echo $randval;
?>
Or you can use mt_rand() which is seeded differently on each execution.

Timepicker that removes times as they're selected (ajax)

I'm building a booking form for a moving business that uses a calendar combined with a start and end time. I built the timepicker with Formidable Pro, and it allows me to check "unique" on time fields which automatically removes them on the selected date. However it doesn't automatically remove the times from within the range between start and end times (ie: if someone chooses to rent a truck from 1am-3am I need 1am,2am,and 3am to be removed from future options but right now it only removes 1am and 3am) . I need to write ajax to remove the in-between times from the options. I'm not sure where to begin. This is the current ajax_time_ options function. Any push in the right direction would be appreciated.
function ajax_time_options(){
global $frmpro_settings, $frmdb, $wpdb;
//posted vars = $time_field, $date_field, $step, $start, $end, $date, $clock
extract($_POST);
$time_key = str_replace('field_', '', $time_field);
$date_key = str_replace('field_', '', $date_field);
if (!preg_match('/^\d{4}-\d{2}-\d{2}$/', trim($date)))
$date = FrmProAppHelper::convert_date($date, $frmpro_settings->date_format, 'Y-m-d');
$date_entries = FrmEntryMeta::getEntryIds("fi.field_key='$date_key' and meta_value='$date'");
$opts = array('' => '');
$time = strtotime($start);
$end = strtotime($end);
$step = explode(':', $step);
$step = (isset($step[1])) ? ($step[0] * 3600 + $step[1] * 60) : ($step[0] * 60);
$format = ($clock) ? 'H:i' : 'h:i A';
while($time <= $end){
$opts[date($format, $time)] = date($format, $time);
$time += $step;
}
if($date_entries and !empty($date_entries)){
$used_times = $wpdb->get_col("SELECT meta_value FROM $frmdb->entry_metas it LEFT JOIN $frmdb->fields fi ON (it.field_id = fi.id) WHERE fi.field_key='$time_key' and it.item_id in (". implode(',', $date_entries).")");
if($used_times and !empty($used_times)){
$number_allowed = apply_filters('frm_allowed_time_count', 1, $time_key, $date_key);
$count = array();
foreach($used_times as $used){
if(!isset($opts[$used]))
continue;
if(!isset($count[$used]))
$count[$used] = 0;
$count[$used]++;
if((int)$count[$used] >= $number_allowed)
unset($opts[$used]);
}
unset($count);
}
}
echo json_encode($opts);
die();
}

Smarty Date Difference

Please post any smarty syntax to Get number of days between two dates from my database. i was to able to display all the other fields,but this date field with number of days not working as the way i was expected.Please let me know is there any way to get this solution without any smarty additional plugins.
Smarty does not include any specific functions for doing date math operations. They have the date_format for timestamps, but otherwise you'd either have to write your own days_diff plugin, find one online, or do the date math in PHP and assign to a new variable in Smarty.
Here is my function for this problem:
/*
* Smarty plugin
* -------------------------------------------------------------
* Type: function
* Name: date_diff
* Author: Rafał Pawlukiewicz
* Purpose: factor difference between two dates in days, weeks, or years
* Input: d1 = "mm/dd/yyyy" or "yyyy/mm/dd" or "yyyy-mm-dd"
* d2 = "mm/dd/yyyy" or "yyyy/mm/dd" or "yyyy-mm-dd" or $smarty.now
* assign = name of variable to assign difference to
* interval = "days" (default), "weeks", "years"
* Examples: {date_diff d1="2020-01-20"}
* Examples: {date_diff d1="2020-01-20" d2=2020-02-10 interval="weeks"}
* Examples: {date_diff d1="2020-01-20" d2=2020-02-10 assign="variable_diff"} result: {$variable_diff}
* -------------------------------------------------------------
*/
function smarty_function_date_diff($params, &$smarty)
{
$d1 = isset($params['d1']) ? $params['d1'] : date('Y-m-d');
$d2 = isset($params['d2']) ? $params['d2'] : date('Y-m-d');
$assign_name = isset($params['assign']) ? $params['assign'] : '';
$date1 = strtotime($d1);
$date2 = strtotime($d2);
// use current for empty string
if (! $date1) {
$date1 = date('Y-m-d');
}
if (! $date2) {
$date2 = date('Y-m-d');
}
$interval = isset($params['interval']) ? $params['interval'] : 'days';
// diff in days
$diff = ($date2 - $date1) / 60 / 60 / 24;
if ($interval === "weeks") {
$diff /= 7;
}
elseif ($interval === "years") {
$diff /= 365.25;
}
$diff = floor($diff);
if ($assign_name) {
$smarty->assign($assign_name, $diff);
}
else {
return $diff;
}
}

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