Futhark by Example

Futhark is really such a great idea. I'm not convinced that dependent types are worth the cognitive overhead in general, but it's definitely worth it to include the length as part of the type information for dynamic arrays, e.g.:

  concat(Vec<T, n>, Vec<T, m>) -> Vec<T, n+m>
  matmul(Mat<T, n, m>, Mat<T, m, l>) -> Mat<T, n, l>
  head(Vec<T, n+1>) -> (T, Vec<T, n>)

This would have saved me so much headache debugging CUDA kernels and numpy!! I wish it were a first-class feature in those frameworks, and even general-purpose languages, but alas.

It would be nice to not name your language after another language. (Yes I know it's a script, that doesn't change my point). I came here expecting something else.

Was expecting to see some examples of how to read runes, but I am nonetheless equally satisfied.

https://en.wikipedia.org/wiki/Elder_Futhark

Futhark is a glimmer of light in the wasteland of C/C++ styled low level GPU languages.

Futhark is pretty great! And I have to say that the maintainer is insanely quick. It has happened on more than one occasion that I reported a bug and it's solved within the day. I have been using Futhark in prod for two years now and never had serious problems.

Couldn’t have chosen a more difficult (and ambiguous) name to pronounce, could you? It almost sounds like a curse that I often hear people say out in the bad streets of New York City.

  concat(Vec<T, n>, Vec<T, m>) -> Vec<T, n+m>
  matmul(Mat<T, n, m>, Mat<T, m, l>) -> Mat<T, n, l>
  head(Vec<T, n+1>) -> (T, Vec<T, n>)

This would have saved me so much headache debugging CUDA kernels and numpy!! I wish it were a first-class feature in those frameworks, and even general-purpose languages, but alas.

Here they are in Futhark:

    val concat [n] [m] 't : (xs: [n]t) -> (ys: [m]t) -> *[n + m]t
    val matmul [n] [m] [l] 't : (xs: [n][m]t) -> (ys: [m][l]t) -> *[n][l]t
    val head [n] 't : (x: [n]t) -> t

And here's the pathological case (length cannot be determined at compile time):

    val filter [n] 'a : (p: a -> bool) -> (as: [n]a) -> *[]a

Other pathological cases include conditionals and loops.

You can do this with templates in C++ and generics in Rust I'm pretty sure. I think the Eigen C++ library supports this. (I have yet to do a linear algebra heavy Rust project, so I can't speak to the options that exist there.)

It would be nice to not name your language after another language. (Yes I know it's a script, that doesn't change my point). I came here expecting something else.

Yeah, when naming your language, it's important to keep mind the expectations of people seeing headlines about articles about your language on blog aggregation sites :^)

Now I'm thinking about "Smalltalk by Example" and "Slang by Example"

Jackson Crawford's youtube channel is very helpful academic source.

For those that don't know, Futhark is comes from the first 6 letters of the runic alphabet (F, U, Þ, A, R, K)

https://www.youtube.com/@JacksonCrawford

Same here, I was very confused for a bit.

Was expecting to see some examples of how to read runes, but I am nonetheless equally satisfied.

https://en.wikipedia.org/wiki/Elder_Futhark

Same. Thought I had a copy of Uthark [1][2] on my shelf too but alas I seem to have only retained Svartkonst [3] during the tragic downsizing of my library.

[1] https://archive.org/details/karlsson-thomas-uthark-nightside...

[2] https://www.84cxrarebooks.com/pages/books/090763/t-ketola-th...

[3] https://www.miskatonicbooks.com/product/thursakyngi-iv-svart...

Futhark is a glimmer of light in the wasteland of C/C++ styled low level GPU languages.

We also need to have StarLisp back, it would be quite fitting.

Interesting, what do use it for if you can share?

What is your use case?

Couldn’t have chosen a more difficult (and ambiguous) name to pronounce, could you? It almost sounds like a curse that I often hear people say out in the bad streets of New York City.

Here they are in Futhark:

    val concat [n] [m] 't : (xs: [n]t) -> (ys: [m]t) -> *[n + m]t
    val matmul [n] [m] [l] 't : (xs: [n][m]t) -> (ys: [m][l]t) -> *[n][l]t
    val head [n] 't : (x: [n]t) -> t

And here's the pathological case (length cannot be determined at compile time):

    val filter [n] 'a : (p: a -> bool) -> (as: [n]a) -> *[]a

Other pathological cases include conditionals and loops.

Yeah, when naming your language, it's important to keep mind the expectations of people seeing headlines about articles about your language on blog aggregation sites :^)

Now I'm thinking about "Smalltalk by Example" and "Slang by Example"

Jackson Crawford's youtube channel is very helpful academic source.

For those that don't know, Futhark is comes from the first 6 letters of the runic alphabet (F, U, Þ, A, R, K)

https://www.youtube.com/@JacksonCrawford

Same here, I was very confused for a bit.

Elder [0] and Younger [1] Futhark (or Fuþark) are the name of two runic writing systems used by Germanic and Scandinavian Vikings. The name Futhark is a combination of the first 6 runes /f/, /u/, /ð/, /ɑ/, /r/, and /k/. Similar to how you get the name "alphabet" from the first two letters of Greek's writing system.

[0]: https://en.wikipedia.org/wiki/Elder_Futhark

[1]: https://en.wikipedia.org/wiki/Younger_Futhark

I'm talking about cases where the array size is not known at compile time. For example, say the user passes in a list of numbers as command line arguments. Then we have

  argv: Vec<String, argc>

If I want to map these to ints, then I'd like a compile-time guarantee that the resulting array

  nums: Vec<Int, argc>

is the same length as argv. Lean and Idris can do this, but AFAIK no commonly used languages can. But unlike general dependent types, these are not hard to wrap one's head around and would save a lot of frustration, in my experience.

Yeah, C++ arrays are literally that.

[0]: https://en.wikipedia.org/wiki/Elder_Futhark

[1]: https://en.wikipedia.org/wiki/Younger_Futhark

I'm talking about cases where the array size is not known at compile time. For example, say the user passes in a list of numbers as command line arguments. Then we have

  argv: Vec<String, argc>

If I want to map these to ints, then I'd like a compile-time guarantee that the resulting array

  nums: Vec<Int, argc>

Same. Thought I had a copy of Uthark [1][2] on my shelf too but alas I seem to have only retained Svartkonst [3] during the tragic downsizing of my library.

[1] https://archive.org/details/karlsson-thomas-uthark-nightside...

[2] https://www.84cxrarebooks.com/pages/books/090763/t-ketola-th...

[3] https://www.miskatonicbooks.com/product/thursakyngi-iv-svart...

We also need to have StarLisp back, it would be quite fitting.

What is your use case?

Interesting, what do use it for if you can share?

Optimization algorithms. The build in automatic differentiation is great!.

Yeah, C++ arrays are literally that.

Arrays are not dynamically sized though (handling runtime sizes) and don’t have efficient append/concat. The point of the dependent types is that you can have the type system track that concat creates an M+N length vector, sort preserves length (and adds a sorted guarantee that slice preserves), etc. Sure you can do a lot with templates, but that’s advanced templates not just “C++ arrays” in a throwaway “literally that” way.

Optimization algorithms. The build in automatic differentiation is great!.

The following is a hands-on introduction to Futhark through a collection of commented programs, listed in roughly increasing order of complexity. You can load the programs into the interpreter to experiment with them. For a conventional introduction to the language, Parallel Programming in Futhark may be a better choice. For more examples, you can check our implemented benchmarks. We also maintain a list of projects using Futhark.

Some of the example programs use directives for plotting or rendering graphics.

Basic language features

Programming techniques

Automatic differentiation

Literate Futhark

Plotting

Literate Futhark allows direct use of gnuplot. These examples show simple and common cases.

Plotting a histogram

Examples from Dex

The following examples are ported from Dex, a dependently typed functional array language that uses a somewhat different approach to describing loop processing. We've tried to keep the original naming scheme and programming style.

External examples

OCaml-GPU wordcount example by calling Futhark.

Projects using Futhark

The majority of written Futhark code is probably still Futhark’s own test and benchmark suites. However, there are some programs that have been written in Futhark because it was a good tool for the job, and not just to test the compiler. A possibly incomplete list:

Diving Beet is a falling sand game, which is a kind of simple particle simulator toy. Its main purpose is to produce pretty effects. There is a blog post with details and a video.

Futball is a game about avoiding getting hit by balls. The rendering engine is a ray tracer written in Futhark.

Futcam is an application that applies stacks of interactively configurable filters to a webcam stream. Futhark is used to implement the filters.

Futracer is a fairly slow brute-force ray tracer written in Futhark.

Futswirl is a fractal generator based on iterated function systems.

Neptune is an implementation of the Poseidon hash function tuned for Filecoin, where the GPU parts have been implemented in Futhark.

Palathark is a Futhark implementation of the lattice Boltzmann method.

Ray Tracing in One Weekend in Futhark and Ray Tracing: the Next Week in Futhark are implementations based on Peter Shirley's book series. These are by no means real-time ray tracers, but support advanced effects and make use of acceleration structures like BVH trees.

Pareas is a compiler implemented in Futhark and C++.

Hacker Times