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  • Using machine learning to aim mirrors in a solar array?

    - by Buttons840
    I've been thinking about solar collectors where several independent mirrors to focus the light on a solar collector, similar to the following design from Energy Innovations. Because there will be flaws in the assembly of this solar array, I am proceeding with the following assumptions (or lack thereof): The software knows the "position" of each mirror, but doesn't know how this position relates to the real world or to other mirrors. This will account for poor mirror calibration or other environmental factors which may effect one mirror but not the others. If a mirror moves 10 units in one direction, and then 10 units in the opposite direction, it will end up where it originally started. I would like to use machine learning to position the mirrors correctly and focus the light on the collector. I expect I would approach this as an optimization problem, optimizing the mirror positions to maximize the heat inside the collector and the power output. The problem is finding a small target in a noisy high-dimensional space (considering each mirror has 2 axis of rotation). Some of the problems I anticipate are: cloudy days, even if you stumble upon the perfect mirror alignment, it might be cloudy at the time noisy sensor data the sun is a moving target, it moves along a path, and follows a different path every day - although you could calculate the exact position of the sun at any time, you wouldn't know how that position relates to your mirrors My question isn't about the solar array, but possible machine learning techniques that would help in this "small target in a noisy high dimensional-space" problem. I mentioned the solar array because it was the catalyst for this question and a good example. What machine learning techniques can find such a small target in a noisy high-dimensional space? EDIT: A few additional thoughts: Yes, you can calculate the suns position in the real world, but you don't know how the mirrors position is related to the real world (unless you've learned it somehow). You might know the suns azimuth is 220 degrees, and the suns elevation is 60 degrees, and you might know a mirror is at position (-20, 42); now tell me, is that mirror correctly aligned with the sun? You don't know. Lets assume you have some very sophisticated heat measurements, and you know "with this heat level, there must be 2 mirrors correctly aligned". Now the question is, which two mirrors (out of 25 or more) are correctly aligned? One solution I considered was to approximate the correct "alignment function" using a neural network which would take the suns azimuth and elevation as input and output a large array with 2 values for each mirror which correspond to the 2 axis of each mirror. I'm not sure what the best training method is though.

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  • If your unit test code "smells" does it really matter?

    - by Buttons840
    Usually I just throw my unit tests together using copy and paste and all kind of other bad practices. The unit tests usually end up looking quite ugly, they're full of "code smell," but does this really matter? I always tell myself as long as the "real" code is "good" that's all that matters. Plus, unit testing usually requires various "smelly hacks" like stubbing functions. How concerned should I be over poorly designed ("smelly") unit tests?

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  • Merging similar graphs based solely on the graph structure?

    - by Buttons840
    I am looking for (or attempting to design) a technique for matching nodes from very similar graphs based on the structure of the graph*. In the examples below, the top graph has 5 nodes, and the bottom graph has 6 nodes. I would like to match the nodes from the top graph to the nodes in the bottom graph, such that the "0" nodes match, and the "1" nodes match, etc. This seems logically possible, because I can do it in my head for these simple examples. Now I just need to express my intuition in code. Are there any established algorithms or patterns I might consider? (* When I say based on the structure of the graph, I mean the solution shouldn't depend on the node labels; the numeric labels on the nodes are only for demonstration.) I'm also interested in the performance of any potential solutions. How well will they scale? Could I merge graphs with millions of nodes? In more complex cases, I recognize that the best solution may be subject to interpretation. Still, I'm hoping for a "good" way to merge complex graphs. (These are directed graphs; the thicker portion of an edge represents the head.)

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  • Where can I learn to write my own database?

    - by Buttons840
    I'm interested in writing my own database - a triple-store. Are there any good resources to help with the challenges of such a project? Or more generally: How can I learn to write my own database? Some specific issues I'm unsure of: How is the data actually stored on the file-system? A flat-file seems easy enough, but a database is a lot more then a flat-file. What kinds of things are typically stored (or cached) in memory? How are indexes created and stored? How is ACID compliance achieved? Etc. This is a big topic, but knowing how to store large amounts of data in a reliable way is good to know. (My investigation into existing triple-stores was summarized back in 2008; not much has changed in 4 years it seems. This is why I want write my own.)

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