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Weekly Report 03/04/15

08

Apr

2015

Continued hunting for the bug in the NNTSC live exporter with mixed success. I've narrowed it down to definitely being the per-client queue that is the problem and it doesn't appear to be due to any obvious slowness inserting into the queue. Unfortunately, the problem seems to only occur once or twice a day so it takes a day before any changes or additional debugging take effect.

Went back to working on the mechanical Turk app for event detection. Finally finished a tutorial that shows most of the basic event types and how to classify them properly. Got Brendon and Brad to run through the tutorial and tweaked it according to their feedback. The biggest problem is the length of the tutorial -- it takes a decent chunk of our survey time to just run through the tutorial so I'm working on ways to speed it up a bit (as well as event classification in general). These include adding hot-keys for significance rating and using an imagemap to make the "start time" graph clickable.

Spent a decent chunk of my week trying to track down an obscure libtrace bug that affected a couple of 513 students, which would cause the threaded I/O to segfault whenever reading from the larger trace file. Replicating the bug proved quite difficult as I didn't have much info about the systems they were working with. After going through a few VMs, I eventually figured out that the bug was specific to 32 bit little-endian architectures: due to some lazy #includes, the size of an off_t was either 4 to 8 bytes between different parts of the libwandio source code which resulted in some very badly sized reads. The bug was found and fixed a bit too late for those affected students unfortunately.

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