Box2D VS minitest

For typical game physics engines... not that much. Math libraries like Eigen or Blaze use lots of template metaprogramming techniques under the hood that can help when you're doing large batched matrix multiplications (since it can remove temporary allocations at compile-time and can also fuse operations efficiently, as well as applying various SIMD optimizations), but it doesn't really help when you need lots of small operations (with mat3 / mat4 / vec3 / quat / etc.). Typical game physics engines tend to use iterative algorithms for their solvers (Gauss-Seidel, PBD, etc...) instead of batched "matrix"-oriented ones, so you'll get less benefits out of Eigen / Blaze compared to what you typically see in deep learning / scientific computing workloads.

The codebases I've seen in many game physics engines seem to all roll their own math libraries for these stuff, or even just use SIMD (SSE / AVX) intrinsics directly. Examples: PhysX (https://github.com/NVIDIA-Omniverse/PhysX), Box2D (https://github.com/erincatto/box2d), Bullet (https://github.com/bulletphysics/bullet3)...

Box2D: 2D engine used in Unity and also earlier versions of Godot. Open source.

Box2D GitHub repo: erincatto/box2d

Why is 600 lines too long? How are you able to make that judgment call without first knowing what the algorithm is even doing? People setting arbitrary limits like this is what leads to convoluted spaghetti, instead of just taking things on a case by case basis. Here’s a function from the Box2D code running a particularly complex algorithm for solving contact velocities https://github.com/erincatto/box2d/blob/411acc32eb6d4f2e96fc... .

It’s 310 lines long. It reads very well, and it looks very maintainable. It has very clear comments explaining the reasoning behind the harder parts of the code. Would you reject this code because it’s pretty long? I wouldn’t.

There is no such thing as too long or too short. There’s overengineered and there’s underengineered and there’s a sweet spot in the middle that has the perfect amount of engineering with the least amount of complexity (preferably no additional complexity than the original problem warranted). Sometimes, the problem at hand is inherently a large algorithm and requires many lines of code. Don’t split it up! It just makes it harder for future maintainers who now have to figure out if the additional functions are actually being used elsewhere or if they’re just there to make the code “pretty”.

There is always the approach of looking at how an existing engine is implemented, such as box2d: https://github.com/erincatto/box2d

TIL Box2D must not be serious code because it doesn't use copious amounts of explicit temporaries[0].

And just for the record, I'm very glad Erin Catto decided to use operator overloading in his code. It made it much easier for me to read and understand what the code was doing as opposed to it being overly verbose and noisy.

[0]: https://github.com/erincatto/box2d/blob/main/src/collision/b...

For Physics Box2d can be used as a simple starting point.

I suspect most C++ physics libraries like Box2D (https://github.com/erincatto/box2d) or Bullet3 (https://github.com/bulletphysics/bullet3) could really benefit a lot from SIMD.

for 2D physics have a look at Box2D it's amazing https://box2d.org/

In this part, we’ll set up our testing environment so that we can test our Rails API using minitest with minitest/spec. We’ll look at the differences between traditional style unit tests and spec-style tests, or specs. I’ll demonstrate why you should use minitest-rails. We’ll look at using rack-test for testing our API. We’ll even create our own generator to generate API specs.

I forgot to mention that reading code is also a good way to learn how to write code, it's like inspiration. Check repos of some gems you like. For example sidekiq https://github.com/sidekiq/sidekiq/tree/main/lib/sidekiq Or minitest https://github.com/minitest/minitest/tree/master/lib/minitest

All through GitHub.

1. From https://github.com/rails/rails/blob/6ffb29d24e05abbd9ffe3ea9..., click "Blame" on the header bar over the file contents.

2. Scroll down to the line and click on the commit in the left column.

3. Scroll down to the file that removed the line from its previous file, activesupport/lib/active_support/test_case.rb.

4. Click the three-dots menu in that file's header bar and select "View file".

5. Click "History" in the header bar of the contributors, above the file contents.

6. I guessed here at commit 281f488 on its message: "Use the method provided by minitest to make tests order dependent". There's a comment here that identified the problem which led to, and provided context for, the change in 6ffb29d.

The OP is from minitest's documentation, so to find the introduction in minitest, it's basically the same process.

1. Go to https://github.com/minitest/minitest.

2. Search the repo for the method name. Even just "i_suck" will match the commit.

3. Select the oldest commit in the results. That's a4553e2.

The new test convention is now "test/**/test_*.rb" instead of "test/**/*_test.rb". For example, Puma and Minitest are popular repositories using this naming pattern.

https://github.com/seattlerb/minitest really removed the FUD for me when i started learning Ruby and Rails. Its full of metaprogramming and fancy tricks but is also quite small, practical and informal in its style.

e.g. "assert_equal" is really just "expected == actual" at it's core but it uses both both a block param (a kind of closure) for composing a default message and calls "diff" which is a dumb wrapper around the system "diff" utility (horrors!). There is even some evolved nastiness in there for an API change that uses the existing assert/refute logic to raise an informative message. this is handled with a simple if and not some sort of complex hard-to-follow factory pattern or dependency injection misuse.

https://github.com/seattlerb/minitest/blob/master/lib/minite...

Those are just a few examples of what you can do with Minitest! Check out their README on GitHub and keep on exploring.

One of the things I love the most about Ruby is that it tends to coalesce around one or two really popular libraries. Rails is the big one obviously, but over time you see libraries designed for a particular purpose "winning" over other things. This includes things like linting/code analysis (Rubocop), authentication (Devise), testing (RSpec and Minitest) and more. The emphasis is on making something good great rather than making a lot of different good things.

Then try minitest (unit and spec verisons) https://github.com/seattlerb/minitest