Slashdot Mirror
Parallel Programming For the Arduino
blackbearnh writes "As more non-traditional programmers start playing around with embedded platforms like the Arduino, the limitations and complications of interrupt-driven event handling can become an annoying barrier to entry. Now a group of academics have ported the parallel-processing language Occam to the Arduino. In an interview on O'Reilly Answers, Matt Jadud of Allegheny College describes how Occam helps artists using the Arduino in their installations, and how the advent of low-cost computing platforms is changing the educational experience for proto-makers in school. 'Basically, an artist or a tinkerer or a hacker has a goal. They don't really care about learning Occam. They don't care about how this language is different from C. They just want to make a cat door that keeps their cat out when the cat comes back with a mouse. Or they want to make some kind of installation piece. Trying to focus as much on the user and the possible goals they might have is what's motivating our work right now.'"
"They don't really care about learning Occam. They don't care about how this language is different from C. They just want to make a cat door that keeps their cat out when the cat comes back with a mouse. Or they want to make some kind of installation piece. Trying to focus as much on the user and the possible goals they might have is what's motivating our work right now."
Isn't this kind of thinking that lead us to why we have the security holes, shoddy programming, and bloat-ware today? People just want to code and not to learn the ins and outs required to craft a well-heeled, tuned, and functioning program or application?
just implement simple threading
Sure, and they could just learn to fly too, instead of relying on some convenient form of transportation that solves the problem for them.
Threads are the famed "simple, clean and wrong" general solution to parallel programming tasks. The *concept* and *implementation* of threads can be simple, sure, but if you're working on anything other than simple problems, the trouble of keeping track of everything that's going on can become very challenging very quickly.
a whole other language just for one problem.
It's a big problem. Learning another language is generally a smaller problem. Particularly if you're the kind of Real Programmer(TM) that we're probably going to hear can manage with threads just fine.
Tweet, tweet.
occam iits sh like all lel lanparalguages.
In my limitted experience, threads are one of the more difficult things for... people to understand. I find it difficult to describe their position, which I think Matt Jadud had a tough time too, (See how he said "an artist or a tinkerer or a hacker"). In my situation, I have a friend who is taking an engineering major at the local university. Now, a little background information; I don't know how it is in other cities across the world, but here, Engineering at the university is considered one of the hardest courses. You know, really ridiculously high drop out rates, cause most people can't handle it. Opening orientation, they say look to your left, look to your right. 2 out of the 3 of you won't make it past second year. So anyone who manages to make it through the first 2 years of Engineering gets this perception that they know to do stats as well as a stats major or know how to program as good as a programming major.
Anyways, so my buddy is in engineering, and he knows enough C++ to essentially do any calculation he wants through the command line. He hasn't had to work with GUI's or anything like that. The most he did was a turn based Star Trek game where the command prompt simply reprints the "game board" everytime you make a move or perform an attack, prompting the player what to do at the end of each turn.
So he tends to be the kind of user that they target with these kinds of ports. He's already loaded with a bunch of information in some other field. Be it engineering, arts, hacking, radio signals, whatever. They don't have a whole lot of time to run through the tutorials to learn threading and how its supposed to be done properly. There's no telling how long it'll be before they get into an issue with threading and they won't have enough knowledge on how to fix it and it'll be a big headache if they went and built their entire code that revolves around this segfault they created.
So thats where these other languages come in. They are similar enough to a common language like C that anyone who does a beginner course can pick them up. They offer the features that users WANT without all the complications that come with learning how its done.
I know, I know, teach a man to fish, right? But what if he only ever needs 1 fish in his entire lifetime?
There is no limit to the functionality of Interrupt Service Routines (ISR) and the interrupt-driven "event model," as the OP put it.
Programming an ISR may be difficult, but even the topic of this post, a parallel environment running on the Arduino, will be based upon ISR routines. The user-level programs will not interact with ISRs, but the Ocaml implementation will abstract them.
Fundamentally, the hardware will continue to use interrupts to signal the availability of data from human input devices. Therefore, the fastest and most direct way to access this data is to write an assembly language ISR. The difficulty is that embedded systems programming such as this requires specialized technical knowledge on the part of the programmer.
Clearly the Ocaml solution posted will ease the burden on the coder, and that is a good thing. But the way it works is not that it no longer uses ISRs. It almost certainly implements its own ISRs and polling routines. In this way, it will be like a library. The beneficial result is that individual programmers do not have to reimplement the ISRs. But there is no benefit in, and no possibility of, eliminating the very needed ISR itself.
Personally, I question whether the MCUs selected for the Arduino are appropriate for the "cute tech" market that the Arduino-series-PCB-module (a.k.a. "shield") manufacturers seem to be going for. Possibly the availability of Ocaml will bring the platform more in line with, e.g., the BasicStamp or similar. Overall, I see an impedence mismatch between what people would like to do (make costumes) and what they get (asking their friends to write code for them).
The fundamental first step will be describing to the Ocaml environment how it is that the peripherals have been wired to the chip. Then the Ocaml environment can, presumably, service these interfaces either through ISRs or polling. We'll see what transpires in simplifying the Arduino software landscape.... ;)
A race condition between two processes is easy. A race condition between three is several times harder. Race conditions between a half dozen processes? Forget about it, at least for the hobbyist.
Race conditions can be notoriously difficult to program around. You can go from 20 lines of code to 200 in a heartbeat with just one or two of them. Get five or six, and your 20 line program needs a thousand lines to deal with it all. That's pretty ridiculous, especially for hobbyists.
If you've got a tool to eliminate the problem completely, why would you poopoo it?
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
The best option for people who want to learn about parallel programming on an embedded processor is the Parallax Propeller. Genuine 8 core system on a chip, programmed to the bare metal. And so much fun.
http://en.wikipedia.org/wiki/Parallax_Propeller
You embed RFID tags in the mice and then keep the door locked if one is detected.
Good idea. I'm impressed that they were able to cram Occam into an Atmel ATMega. Occam syntax is rather clunky by modern standards, but it gets the job done. It has a sane concurrency model and is safer than C.
Next, Ada?