Efficiency Questions

[Night4554]

When coding my website, I want to have a thumbnail of the latest gallery item. But the thumbnail is of a different size than the gallery will automatically generate.

So I have a multitude of options but I'm wonder will be the most efficient in terms of generating the page quickest. (Note: all of this is using GDI)

1) Use a PHP file to generate a thmbnail from the fullsize image everytime. (Or generate it from another thumbnail)

2) Check if a thumbnail is made, if not, generate the thumbnail, then display it using HTML

3) Check if the thumbnail is made, if not, generate the thumbnail, and then make an image reference in PHP of the thumbnail and generate it that way.

As I code the Gallery Program (GALant), I run across instances where I'm say, checking if a file exists. Everytime I load a page. That doesn't seem efficient to me. Are there any papers or topics that discuss this area?

[swr]

2 or 3 would be faster than 1 because it doesn't require generating the image every time.

Checking for the existence of a file isn't so bad. Usually you're about to cause an access to the file anyway, and checking the existence will likely cause some disk reads to occur and be cached, which means the later access will be from the cache. So you shouldn't lose very much.

As a general rule I would recommend NOT worrying about efficiency unless you really are seeing some specific operation slowing down your site, or if you know for certain that it will be. If you start thinking a lot about efficiency it can be very tempting to waste a lot of time optimizing things for speed that were never slow in the first place. It's far more important to make your code clean and readable, that way it'll be easy to come back later and fix the few parts that really do turn out to be slow.

"Premature optimization is the root of all evil." - Donald Knuth