PHP Hashtable array optimisation

Question

I made a PHP app which was taking about ~0.0070sec for execution. Now, I added a hashtable array with about 2000 values. Suddenly the time for execution has gone up to ~0.0700 secs. Almost 10 times the previous value.

I tried commenting out the part where I was searching inside the hashtable array (but array was still left defined). Still, the execution time remains about ~0.0500secs.

Array is something like:

$subjectinfo = array(
        'TPT753' => 'Industrial Training',
        'TPT801' => 'High Polymeric Engineering',
        'TPT802' => 'Corrosion Engineering',
        'TPT803' => 'Decorative ,Industrial And High Performance Coatings',
        'TPT851' => 'Project');

Is there any way to optimize this part?

I cannot use Database as I am running this app on Google app engine which is still not supporting JDO database for php.

Some more code from the app:

function getsubjectinfo($name)
    {
        $subjectinfo = array(
        'TPT753' => 'Industrial Training',
        'TPT801' => 'High Polymeric Engineering',
        'TPT802' => 'Corrosion Engineering',
        'TPT803' => 'Decorative ,Industrial And High Performance Coatings',
        'TPT851' => 'Project');

    $name = str_replace("-", "", $name);
    $name = str_replace(" ", "", $name);
    if (isset($subjectinfo["$name"]))
        return "(".$subjectinfo["$name"].")";
    else
        return "";
   }

Then I am using the following statement 2-3 times in the app:

echo $key." ".$this->getsubjectinfo($key)

@jon I have declared this array only once in my project. Searching inside this array 2 times throughout the app lifetime. — hiprakhar
– hiprakhar, Commented Mar 10, 2011 at 14:12
If every key has TPT in it, try to make the array with integer indices without TPT. Integer indices will work faster — Stanislav Yaglo
– Stanislav Yaglo, Commented Mar 10, 2011 at 14:19

KingCrunch · Accepted Answer · 2011-03-10 15:14:25Z

1

function getsubjectinfo($name)
{
    $subjectinfo = array(
    'TPT753' => 'Industrial Training',
    'TPT801' => 'High Polymeric Engineering',
    'TPT802' => 'Corrosion Engineering',
    'TPT803' => 'Decorative ,Industrial And High Performance Coatings',
    'TPT851' => 'Project');
// ..
}

This way the array is created everytime you call the function. Consider using a static variable here

function getsubjectinfo($name)
{
    static $subjectinfo = array(
    'TPT753' => 'Industrial Training',
    'TPT801' => 'High Polymeric Engineering',
    'TPT802' => 'Corrosion Engineering',
    'TPT803' => 'Decorative ,Industrial And High Performance Coatings',
    'TPT851' => 'Project');
// ..
}

And as a sidenote: You can also use a SQLite-Database :)

Update: An OOP approach

class MyClass {
    public static $subjectnames = array(
      'TPT753' => 'Industrial Training',
      'TPT801' => 'High Polymeric Engineering',
      'TPT802' => 'Corrosion Engineering',
      'TPT803' => 'Decorative ,Industrial And High Performance Coatings',
      'TPT851' => 'Project');

    public function getsubjectinfo($name) {
        $name = str_replace("-", "", $name);
        $name = str_replace(" ", "", $name);
        if (isset(self::$subjectnames["$name"]))
            return "(".self::$subjectnames["$name"].")";
        else
            return "";
    }
}

edited Mar 10, 2011 at 15:14

answered Mar 10, 2011 at 14:47

KingCrunch

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2 Comments

hiprakhar Over a year ago

@kingchurch Thanks! I am doing almost the same by using constructor to define the array.

KingCrunch Over a year ago

Dont see any constructor and it would not change anything: $subjectinfo is a local variable and will get created in a method everytime its call too.

Chris Tonkinson · Accepted Answer · 2011-03-10 14:43:53Z

0

You could try using integers as keys into your table.

"But all keys do not necessarily have TPT, they may be TOE362, AGS612 etc. I have sorted them in ascending order, but wonder if it helped."

Hash your original strings into numeric data, and use that output as your hash keys. Yes, there is a constant-time penalty involved per access (for the extra hash), but if your final data set is large enough, I suspect this may outperform letting PHP use string keys directly.

If all else fails, write the performance sensitive code in C and compile it as a PHP extension. No, better yet, write the whole app in C. Better yet, use direct machine code for everything. Or wire a breadboard with your desired logic! Reference: http://xkcd.com/378/

answered Mar 10, 2011 at 14:43

Chris Tonkinson

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1 Comment

hiprakhar Over a year ago

Thanks the comic strip.. liked it :)

hiprakhar · Accepted Answer · 2011-03-10 15:05:57Z

Lesson of the day learnt- Defining large arrays in the class constructor can speed up the things.

I modified the code as:

class myclass
{
    var $subjectnames = array();
    function myclass()
    {
        $this->subjectnames = array(
    'TPT753' => 'Industrial Training',
    'TPT801' => 'High Polymeric Engineering',
    'TPT802' => 'Corrosion Engineering',
    'TPT803' => 'Decorative ,Industrial And High Performance Coatings',
    'TPT851' => 'Project');
    }


function getsubjectinfo($name)
    {
        //$subjectinfo = array();
        $name = str_replace("-", "", $name);
        $name = str_replace(" ", "", $name);
        if (isset($this->subjectnames["$name"]))
            return "(".$this->subjectnames["$name"].")";
        else
            return "";
    }
}

Jerome WAGNER · Accepted Answer · 2011-03-10 16:07:13Z

0

I once read that you can optimize such a static array configuration via serialize/unserialize.

Inject in your source code the serialized version of the array. It will be a string.

Use unserialize(..) to dynamically build the array.

Urban legend says It might save some parsing time.

another thing you can try is to use object properties instead of array keys.

$obj->TRV3463 may be faster than array access.

answered Mar 10, 2011 at 16:07

Jerome WAGNER

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