underdevelopment

So a little while back ibuildings had this fun contest to build a path finding program that would solve a traveling salesman like problem. The constraints where pretty simple, you got a CSV file with latitude/longitude locations. You started at a certain location and you should end at a certain location. The application should then find the shortest route that touched all locations.

Now I’ll be the first to say that PHP is really not the language for that. A few years back I wrote a pathfinding tool for use with a game called EVE online in which I calculated certain trade routes based on data you could export from the game. After seeing PHP’s performance I switched to Python and more or less sliced the processing time in half if not more. Mainly because Python has specific array like types and PHP just has generic array’s, which with large data sets matters a lot. Perhaps also because my pathfinding-foo was still rather weak

However, back to now and the ibuildings challenge. The challenge would be rated on 3 criteria. Speed, lines of code and code complexity. Personally I could care less about the latter two and focused purely on speed. In the weeks that followed I had a great time comparing execution times with Remi and Andries. I think this was also key to keep diving into it and tweaking it until it was as fast as I could get it.

Sadly, my submission actually had a off-by-one bug in it which more or less instantly disqualified my entry. Yes, bit of a bummer, but such is life.

Now I had already decided to publish my code after the contest, however sadly I never really found the time to type this up. So a bit late but here is the code for my solution for the ibuildings elephpant challenge.

Below is the submitted code, and a link to download the code and original test data file so you can try it out for yourself.

download the code – Just unpack and run via php contest.php elephpant_landmarks.csv

-edit-

Ok scratch the code, I’m having some trouble with getting it to play nice. Just download the tar.gz and view the code in your favorite editor.

admin PHP, software development code, performance, spielerij, techniques, traveling salesman

Sometimes in applications you will have certain user settings that you want to apply, even when the user is not logged in. Take for instance these examples:

• “welcome back <name>” msg on return.
• You have a portal type page where the user can control what content is shown where
• You want to track where the user was when he last visited the site, perhaps to offer him the option to return to there.

I recently needed some functionality like that. So I’ve created a object that can help me with that.

I thought about it for a moment and created a singleton settings object for me to call upon to set and retrieve certain settings. Now I have to warn you that there is a small problem with singletons, if you use unit testing it can be difficult to control the behaviour of singletons over multiple tests. So be wary of this when you are running unit tests.

I also wrap all data in a separate array. This isn’t really necessary, but it makes handling the data a lot easier. If you wanted you could also add some sort of encryption to the cookie data so that users couldn’t easily tamper with it.

admin PHP, software development design patterns, object oriented programming, PHP, singleton, techniques

Transparency in HTML/CSS is largely an already solved problem, recent browsers all seem to handle PNG transparency pretty well and there are scripts that will make sure older browsers will handle them as well.

However, I wanted to make a post about a little technique I rarely see used which I think is quite genius in it’s simplicity.  Whenever you want to create a semi-transparent surface you create a gif file that contains a simple pattern of transparent and opaque pixels; as in the example on the right.  The white you see in the chequered image is of course transparent.

So let’s demonstrate how this effect actually looks.

Now as you can see the effect itself is very specific, and different backgrounds have different outcomes for the effect. Which might not fit every design. Another disadvantage is that it can only be used to show a 50% transparency effect. There might be pixel patterns that will give you a different distribution but I’ve never seen them.

The biggest advantage however is that you don’t need any fancy CSS or javascript or PNG, which in certain specific cases can be a big plus.  It’s more of a hack on your eyes/brain then on the browser

admin design CSS, design, HTML, techniques, tricks