Crash your code – Lessons Learned From Debugging Things That Should Never Happen™

Let’s be honest, no one likes to see their program crash. It’s a clear sign that something is wrong with our code, and that’s a truth we don’t like to see. We try our best to avoid such a situation, and we’ve seen how compiler warnings and other static code analysis tools can help us to detect and prevent possible flaws in our code, which could otherwise lead to its demise. But what if I told you that crashing your program is actually a great way to improve its overall quality? Now, this obviously sounds a bit counterintuitive, after all we are talking about preventing our code from misbehaving, so why would we want to purposely break it?

Wandering around in an environment of ones and zeroes makes it easy to forget that reality is usually a lot less black and white. Yes, a program crash is bad — it hurts the ego, makes us look bad, and most of all, it is simply annoying. But is it really the worst that could happen? What if, say, some bad pointer handling doesn’t cause an instant segmentation fault, but instead happily introduces some garbage data to the system, widely opening the gates to virtually any outcome imaginable, from minor glitches to severe security vulnerabilities. Is this really a better option? And it doesn’t have to be pointers, or anything of C’s shortcomings in particular, we can end up with invalid data and unforeseen scenarios in virtually any language.

It doesn’t matter how often we hear that every piece of software is too complex to ever fully understand it, or how everything that can go wrong will go wrong. We are fully aware of all the wisdom and cliches, and completely ignore them or weasel our way out of it every time we put a /* this should never happen */ comment in our code.

So today, we are going to look into our options to deal with such unanticipated situations, how we can utilize a deliberate crash to improve our code in the future, and why the average error message is mostly useless.

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Screen Shake In VR, Minus The Throwing Up

In first-person games, an effective way to heighten immersion is to give the player a sense of impact and force by figuratively shaking the camera. That’s a tried and true practice for FPS games played on a monitor, but to [Zulubo]’s knowledge, no one has implemented traditional screen shake in a VR title because it would be a sure way to trigger motion sickness. Unsatisfied with that limitation, some clever experimentation led [Zulubo] to a method of doing screen shake in VR that doesn’t cause any of the usual problems.

Screen shake doesn’t translate well to VR because the traditional method is to shake the player’s entire view. This works fine when viewed on a monitor, but in VR the brain interprets the visual cue as evidence that one’s head and eyeballs are physically shaking while the vestibular system is reporting nothing of the sort. This kind of sensory mismatch leads to motion sickness in most people.

The key to getting the essence of a screen shake without any of the motion sickness baggage turned out to be a mix of two things. First, the shake is restricted to peripheral vision only. Second, it is restricted to an “in and out” motion, with no tilting or twisting. The result is a conveyance of concussion and impact that doesn’t rely on shaking the player’s view, at least not in a way that leads to motion sickness. It’s the product of some clever experimentation to solve a problem, and freely downloadable for use by anyone who may be interested.

Speaking of fooling one’s senses in VR environments, here is a fascinating method of simulating zero gravity: waterproof the VR headset and go underwater.

[via Reddit]

Web Development: What’s Big In 2019?

I try to keep up with web development trends but it’s hard to keep pace since it’s such a fast evolving field. Barely a week goes by without the release of a new JS framework, elaborate build tool or testing suite — all of them touted as the one to learn. Sorting the hype from the genuinely useful is no mean feat, so my aim in this article is to summarise some of the most interesting happenings that web development saw in the last year, and what trends we expect to see more of in 2019.

A technology or framework doesn’t have to be brand new to be on our list here, it just needs to be growing rapidly or evolving in an interesting way. Let’s take a look!

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Project Shows How To Use Machine Learning to Detect Pedestrians

Most people are familiar with the idea that machine learning can be used to detect things like objects or people, but for anyone who’s not clear on how that process actually works should check out [Kurokesu]’s example project for detecting pedestrians. It goes into detail on exactly what software is used, how it is configured, and how to train with a dataset.

The application uses a USB camera and the back end work is done with Darknet, which is an open source framework for neural networks. Running on that framework is the YOLO (You Only Look Once) real-time object detection system. To get useful results, the system must be trained on large amounts of sample data. [Kurokesu] explains that while pre-trained networks can be used, it is still necessary to fine-tune the system by adding a dataset which more closely models the intended application. Training is itself a bit of a balancing act. A system that has been overly trained on a model dataset (or trained on too small of a dataset) will suffer from overfitting, a condition in which the system ends up being too picky and unable to usefully generalize. In terms of pedestrian detection, this results in false negatives — pedestrians that don’t get flagged because the system has too strict of an idea about what a pedestrian should look like.

[Kurokesu]’s walkthrough on pedestrian detection is great, but for those interested in taking a step further back and rolling their own projects, this fork of Darknet contains YOLO for Linux and Windows and includes practical notes and guides on installing, using, and training from a more general perspective. Interested in learning more about machine learning basics? Don’t forget Google has a free online crash course to get you up to speed.

MIT Scratch 3.0 Opens New Doors For Users And Builders Alike

We typically feature projects from people sharing what they’ve learned while building something for themselves. But our community has a healthy contingent who deploy their skills for the benefit of future generations, developing a child’s natural curiosity for play into interest in understanding the technical world they will grow up in. This field is where MIT’s release of Scratch 3.0 can open up interesting possibilities.

Scratch is a block-based programming language designed for elementary school children, letting them learn fundamental concepts while experimenting in an environment filled with visual and audible feedback. In an effort to make Scratch more widely available, version 2.0 in 2013 moved to the web. But it was built using interactive web technology of the time: Adobe Flash. As Flash has fallen out of favor and scheduled to be phased out in 2020, Scratch 3.0 used React to make the shift to HTML5.

The most immediate benefit is that Scratch can now be used on tablets, which all have modern browsers but very few of which have Flash. Another common educational hardware platform is the Raspberry Pi, which supported Scratch 2 via a convoluted software stack that was far from ideal. Now any hardware with a modern browser can run Scratch, no Flash binaries or custom wrappers are required. The Raspberry Pi foundation certainly seemed excited about this change.

But a more exciting and longer term benefit is Scratch extensions, a mechanism for Scratch programs to communicate with external hardware and online resources. This has evolved in parallel with Scratch 2.0 under the experimental ScratchX umbrella and version 3.0 brings it into core. The launch featured a few official extensions (for connecting to micro:bit, LEGO Mindstroms EV3, etc.) with the promise that custom third-party extensions will soon be possible. This will significantly streamline building a Scratch interface for kid-friendly programmable hardware. Something we’ve seen done for a drone, for exploring SDR, and even for a dollhouse. We’ll be keeping an eye out for the official release of Scratch 3.0 custom extension API, but anyone not afraid of working with fluid pre-release code are certainly welcome to dive in right now.

Software: It Is All In The Details

Who’s the better programmer? The guy that knows 10 different languages, or someone who knows just one? It depends. Programming is akin to math, or perhaps it is that we treat some topics differently than others which leads to misconceptions about what makes a good programmer, mathematician, or engineer. We submit that to be a great programmer is less about the languages you know and more about the algorithms and data structures you understand. If you know how to solve the problem, mapping it to a particular computer language should be almost an afterthought. While there are many places that you can learn those things, there is a lot more focus on how to write the languages,  C++ or Java or Python or whatever. We were excited, then, to see [Jeff Erickson] is publishing his algorithms book distilled from teaching at the University of Illinois, Urbana-Champaign for a number of years. The best part? You can read the preprint version online now and it will remain online even after the book goes to print.

When you were in school, you probably learned math in two ways: there was the mechanics (4×4=16) and then there were the word problems (Johnny has 10 candy bars and eats 4, how many are left?). Word problems are usually the bane of the student’s existence, yet they are much more realistic. Your boss has (probably) never come in your office and asked you what 147 divided by 12 is. If she did, you could hand her a calculator. The real value comes in being able to synthesize the right math for the right problem and — if you are lucky — gaining intuition about it (doubling the price will only increase profit by 10%). Software is pretty much the same, for example no one rushes into your cubicle and says “Quick! We need a for loop written!” You get a hazy set of requirements if you are lucky, and you then need to map that into something that computers can do. For that reason, we’ve always been more of a fan of learning about algorithms and data structures rather than specific language features.

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Thread Carefully: An Introduction To Concurrent Python

The ability to execute code in parallel is crucial in a wide variety of scenarios. Concurrent programming is a key asset for web servers, producer/consumer models, batch number-crunching and pretty much any time an application is bottlenecked by a resource.

It’s sadly the case that writing quality concurrent code can be a real headache, but this article aims to demonstrate how easy it is to get started writing threaded programs in Python. Due to the large number of modules available in the standard library which are there to help out with this kind of thing, it’s often the case that simple concurrent tasks are surprisingly quick to implement.

We’ll walk through the difference between threads and processes in a Python context, before reviewing some of the different approaches you can take and what they’re best suited for.

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