For mildred, I have a weighting system that determines which track to queue next. I call this system QBeat. I often try various tweaks to the algorithm for track weighting; trying and get that “perfect mix.” Debugging this system has proven to be a challenge, largely due simply to the amount of time it takes to collect enough data to be able to determine if the system has any quirks. With my current setup, it takes about 4 minutes to calculate the weight of every track in my collection (more about that in another post.) So even queuing things as fast as possible isn’t always a feasible solution for data generation.

So to help me visualize is going with QBeat, I inserted a number of “tracers”, that is, tracks that report their weight every time a new track is added to the queue. This should allow me to do some empirical testing of the system. I really should be working further to develop better unit tests, but what the hell, this is fun.

So without further ado, I present the output from my viz_qbeat script:

http://black.xmtp.net/~ericw/viz_qbeat_snapshot-2007-08-10-17-25.html

The link above is a static version of the page. The live page is updated every five minutes by a cron job. The X axis increments every time a new song is added to the queue. The Y axis is the track’s weight. The list at the bottom is each track, as it was enqueued. A track’s weight rises proportionally with its likeliness of being enqueued.

So what can I learn from this static snapshot? Check out the medium blue line (“Cold Heart” by Project Pitchfork), which starts at a weight of approximately 2.6. At around 38 on the X axis, its weight drops to 1.2. Why did that happen? Looking down through the list of queued tracks, we reach 38, and find that “Inquisition” by Skinny Puppy was queued at that time. While “Inquisition” is not a track by Project Pitchfork, we can see that it is on an album titled Industrial Beatdown, and I happen to know that “Cold Heart” is also on that album. So QBeat worked like it should. Joy.

Here’s a link to the live site: http://black.xmtp.net/~ericw/viz_qbeat.html

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