I’m in a computer architecture class at UT. This is fine and dandy. Recently we got a homework/lab, and some people started noticing that one of the reference functions didn’t perform correctly on all machines. Here’s the offending code:
int test_fitsBits(int x, int n) { int TMin_n = -(1 << (n-1)); int TMax_n = (1 << (n-1)) - 1; return x >= TMin_n && x <= TMax_n; } This function is supposed to return 1 if the number x can be represented as a two’s-complement number with n bits, and 0 otherwise.
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Out of a sample of 6511 random cat images taken from Flickr, 640×640 represents 31% of all image resolutions.
Below is my chart covering the cumulative distribution of the 731 distinct image resolutions:
As we can clearly see, 10% of resolutions make up 75% of images on Flickr.
Also, the average size of a Flickr image is 1.7MB. They recently announced that they have 6 billion images, for a total of 10PB of images.
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Dear Prior Owner of Eric Foner’s “Give Me Liberty!” Second Edition Textbook:
Your note was received intact, whoever you are. And you’re right.
It did make me smile. Thank you.
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Rest performance: It’s a measure of how much rest you can get in a given span of time.
REST performance: It’s a measure of how much REST you can get in a given span of time.
Similar, but subtly and importantly different. My tool will measure the second, but not the first.
https://github.com/lkolbly/perf-rest
Do, check it out. Here’s the sample perf.def.js file, broken up into bite-sized chunks with explanations.
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Recently, a group of researchers at CMU developed a program which uses off-the-shelf 3d models to edit images in 3d. I’m terrible at explaining, so here’s a link to the thing: (also so I don’t lose it…)
http://www.cs.cmu.edu/~om3d/
Also, new panorama!
http://pillow.rscheme.org/uav/panorama3.html
The camera mount changed to be a servo ziptied to a block of wood. My suspicion is that the wood absorbs most of the high-frequency interference we saw with the prior panorama.
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I’m going to start running out of crunch-related names. I better practice my quadcopter flying.
Here’s a telemetry graph of what happens when you lose a propeller mid-flight:
(you may have to click on it to view closer) Note the brownish line, which is the motor 4 output signal. It stays synced (roughly) with the others until 16000 on the X, at which point I lost the prop and the control system pegged the motor throttle to compensate.
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Few things are as stressful as your significant other falling 45 feet and shattering her legs beyond repair. Especially when you caused it.
Let me tell you, it does not do any favors for the relationship.
Thankfully, at least in my case, only the legs broke. The rest of her is apparently happy as a clam despite suffering a more-than-8G impact. The recording instruments measured 8G, but it’s possible the impact was higher:
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Got to fly (quadcopter) this weekend. Also got to fly (airplane) this weekend to New Braunfels, which took me directly over the field I fly my quadcopter in.
Speaking of my quadcopter, I’m starting to work on a new vision landing system. So far I just have test imagery of a pad:
Clearly a downward facing camera. The picture below will back me up on this:
But then where did this picture come from?
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I haven’t gotten a chance to fly (quadcopter) since I last posted. I have, however, gotten a chance to fly (airplane) since I last posted. I think the two are related.
However, I got a Raspberry Pi! It’s running Arch. I named it Helium and put it on my quadcopter, so next week hopefully I have a pi commanding a pixhawk via I2C.
However, only time can tell.
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It’s going to be a few weeks before I talk about something other than my quadcopter.
Until then, these two videos:
http://pillow.rscheme.org/flight1.webm
http://pillow.rscheme.org/flight2.webm
It’s running a Raspberry Pi to run the camera. My plan is to connect it via I2C to the Pixhawk, and to build a servo gimbal for the camera. From there I dunno.
Also, while I was developing the ground station I ended up with this graph:A graph of altitude (centimeters vs.
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