Is there any way to optimize this piece of code to work faster? I'd appreciate any suggestions!
This piece of code processes the transferring of edges during graph creation.
foreach($times_arrival as $city_id => $time_points) {
// if city is not prohibited for transfers and there is and exists any departure times for this city
if (isset($times_departure[$city_id]) && isset($cities[$city_id]))
{
foreach($times_arrival[$city_id] as $t1_info)
{
foreach($times_departure[$city_id] as $t2_info)
{
if ($t1_info[0] != $t2_info[0]) //transfers are allowed only for different passages
{
$t1 = $t1_info[1];
$t2 = $t2_info[1];
$vertex_key = new Vertex($city_id, $t1, 1);
$vertex_key = $vertex_key->toString();
//minimum transfer time is 10 min.
if (date('H:i', strtotime($t2)) > date('H:i', strtotime('+ 10 minutes', strtotime($t1))))
{
$this->graph[$vertex_key][] = new Edge(
NULL,
$vertex_key,
new Vertex($city_id, $t2, 0),
(float) 0,
$f((strtotime($t2) - strtotime($t1)) / 60, 0, 1) //edge weight
);
}
//if transfer is on the bound of the twenty-four hours
else if (date('H:i', strtotime('+ 24 hours', strtotime($t2))) > date('H:i', strtotime('+ 10 minutes', strtotime($t1))))
{
$this->graph[$vertex_key][] = new Edge(
NULL,
$vertex_key,
new Vertex($city_id, $t2, 0),
(float) 0,
$f(strtotime('+ 24 hours', strtotime($t2)) - strtotime($t1) / 60, 0, 1) //edge weight
);
}
}
}
}
}
}
example of variables:
var_dump($times_arrival); //$times_departure have the same structure
array
3 =>
array
0 =>
array
0 => string '1' (length=1)
1 => string '08:12' (length=5)
1 =>
array
0 => string '2' (length=1)
1 => string '08:40' (length=5)
41 =>
array
0 =>
array
0 => string '21' (length=2)
1 => string '12:40' (length=5)
Thank you all! The reason of slow speed was coz of using functions strtotime() and date().
In that case only you can say whether you chose a good or bad algorithm. In my point of view your code not has no extra computations.
Only one recommendation - use Xdebug to profile your code and find out where the bottleneck is, if possible.