Futhark is a

functional Functional may refer to: * Movements in architecture: ** Functionalism (architecture) ** Form follows function * Functional group, combination of atoms within molecules * Medical conditions without currently visible organic basis: ** Functional s ...

array An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming l ...

originally developed at DIKU as part of the HIPERFIT project. It focuses on enabling data parallel programs written in a functional style to be executed with high performance on massively parallel hardware, in particular on

GPU A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mob ...

s. Futhark is strongly inspired by

NESL NESL is a parallel programming language developed at Carnegie Mellon by the SCandAL project and released in 1993. It integrates various ideas from parallel algorithms, functional programming, and array programming languages. The most important ne ...

, and its implementation uses a variant of the flattening transformation, but imposes constraints on how parallelism can be expressed in order to enable more aggressive compiler optimisations. In particular, irregular nested data parallelism is not supported.

Overview

Futhark is a language in the ML family, with an indentation-insensitive syntax derived from

OCaml OCaml ( , formerly Objective Caml) is a general-purpose, multi-paradigm programming language which extends the Caml dialect of ML with object-oriented features. OCaml was created in 1996 by Xavier Leroy, Jérôme Vouillon, Damien Doligez, D ...

Standard ML Standard ML (SML) is a general-purpose, modular, functional programming language with compile-time type checking and type inference. It is popular among compiler writers and programming language researchers, as well as in the development of ...

, and

Haskell Haskell () is a general-purpose, statically-typed, purely functional programming language with type inference and lazy evaluation. Designed for teaching, research and industrial applications, Haskell has pioneered a number of programming lan ...

. The type system is based on Hindley-Milner with a variety of extensions, such as uniqueness types and size-dependent types. Futhark is not intended as a

general-purpose programming language In computer software, a general-purpose programming language (GPL) is a programming language for building software in a wide variety of application domains. Conversely, a domain-specific programming language is used within a specific area. For ex ...

for writing full applications, but is instead focused on writing computational "kernels" (not necessarily the same as a GPU kernel) which are then invoked from applications written in conventional languages.

Examples

Dot product

The following program computes the

dot product In mathematics, the dot product or scalar productThe term ''scalar product'' means literally "product with a scalar as a result". It is also used sometimes for other symmetric bilinear forms, for example in a pseudo-Euclidean space. is an alg ...

of two vectors containing double-precision numbers. def dotprod xs ys = f64.sum (map2 (*) xs ys)) It can also be equivalently written with explicit type annotations as follows. def dotprod (xs: 64) (ys: 64) : f64 = f64.sum (map2 (*) xs ys)) This makes the size-dependent types explicit: this function can only be invoked with two arrays of the same size, and the type checker will reject any program where this cannot be statically determined.

Matrix multiplication

The following program performs

matrix multiplication In mathematics, particularly in linear algebra, matrix multiplication is a binary operation that produces a matrix from two matrices. For matrix multiplication, the number of columns in the first matrix must be equal to the number of rows in the ...

, using the definition of dot product above. def matmul m] (A: m]f64) (B: p]f64) : p]f64 = map (\A_row -> map (\B_col -> dotprod A_row B_col) (transpose B)) A Note how the types enforce that the function is only invoked with matrices of compatible size. Further, this is an example of nested

data parallelism Data parallelism is parallelization across multiple processors in parallel computing environments. It focuses on distributing the data across different nodes, which operate on the data in parallel. It can be applied on regular data structures lik ...

References

{{Parallel computing Functional languages Parallel computing Array programming languages