Another week another QA tool.
This week I'm going to talk about Devel::NYTProf (aka NYTProf).
To start, if you're interested in profilers, you should check out the brief history section of the pod, then take a glance at its features. Until recently, I hadn't been very interested in profiling my code. I didn't really have anything that needed the profiling, and the tools just seemed a bit awkward to me. This changed for me when I saw the output from nytprofhtml (1, 2).
While working on Image-TextMode, I noticed that parsing large (~75k) ANSI files was getting to be pretty slow. I decided to run NYTProf on the parsing code, and here's what I got:
[Image: Profiling - Before]
The putpixel(), width() and height() methods are called for every character/attribute combo stored for the image. This turns out to be a really big inefficiency. I've had some XS code in my back pocket for ANSI parsing, so I decided to whip up a replacement parser using that code and run the profiler again.
[Image: Profiling - After]
Huge win! By moving _read() to XS (including putpixel, width, and height) I was able to shave over a second off of the total time (_read inclusive goes from 1.3 seconds to 0.03). Although working with XS was a bit of a pain, it was really great to see such a speed improvement.
I recommend everyone take a look at NYTProf if you're looking find speed inefficients in your code.
