ocaml-multicore / effects-examples

Examples to illustrate the use of algebraic effects in Multicore OCaml

📢 Note 📢

Multicore OCaml project has now been merged into OCaml 🎉. This repository is no longer developed or maintained. Please follow the updates at the OCaml Github repository.

Citation

If you are citing this work in an academic paper, please cite the ICFP 2020 paper "Retrofitting Parallelism onto OCaml": https://dl.acm.org/doi/10.1145/3408995

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Branch trunk	Branch 4.14	Branch 4.13	Branch 4.12

README

Overview

OCaml is a functional, statically-typed programming language from the ML family, offering a powerful module system extending that of Standard ML and a feature-rich, class-based object system.

OCaml comprises two compilers. One generates bytecode which is then interpreted by a C program. This compiler runs quickly, generates compact code with moderate memory requirements, and is portable to many 32 or 64 bit platforms. Performance of generated programs is quite good for a bytecoded implementation. This compiler can be used either as a standalone, batch-oriented compiler that produces standalone programs, or as an interactive REPL system.

The other compiler generates high-performance native code for a number of processors. Compilation takes longer and generates bigger code, but the generated programs deliver excellent performance, while retaining the moderate memory requirements of the bytecode compiler. The native-code compiler currently runs on the following platforms:

	Tier 1 (actively maintained)	Tier 2 (maintained when possible)
x86 64 bits	Linux, macOS, Windows, FreeBSD	NetBSD, OpenBSD
x86 32 bits	Linux, Windows	FreeBSD, NetBSD, OpenBSD
ARM 64 bits	Linux, macOS	FreeBSD
ARM 32 bits	Linux	FreeBSD, NetBSD, OpenBSD
Power 64 bits	Linux
Power 32 bits	Linux
RISC-V 64 bits	Linux
IBM Z (s390x)	Linux

Other operating systems for the processors above have not been tested, but the compiler may work under other operating systems with little work.

Copyright

All files marked "Copyright INRIA" in this distribution are Copyright © 1996-2021 Institut National de Recherche en Informatique et en Automatique (INRIA) and distributed under the conditions stated in file LICENSE.

Installation

See the file INSTALL.adoc for installation instructions on machines running Unix, Linux, macOS, WSL and Cygwin. For native Microsoft Windows, see README.win32.adoc.

Documentation

The OCaml manual is distributed in HTML, PDF, and Emacs Info files. It is available at

https://ocaml.org/releases/latest/manual.html

Availability

The complete OCaml distribution can be accessed at

https://ocaml.org/docs/install.html

Keeping in Touch with the Caml Community

There is an active and friendly discussion forum at

https://discuss.ocaml.org/

The OCaml mailing list is the longest-running forum for OCaml users. You can email it at

[email protected]

You can subscribe and access list archives via the Web interface at

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An alternative archive of the mailing list is also available at

https://inbox.ocaml.org/

There also exist other mailing lists, chat channels, and various other forums around the internet for getting in touch with the OCaml and ML family language community. These can be accessed at

https://ocaml.org/community/

In particular, the IRC channel #ocaml on Libera has a long history and welcomes questions.

Bug Reports and User Feedback

Please report bugs using the issue tracker at https://github.com/ocaml/ocaml/issues

To be effective, bug reports should include a complete program (preferably small) that exhibits the unexpected behavior, and the configuration you are using (machine type, etc).

For information on contributing to OCaml, see HACKING.adoc and CONTRIBUTING.md.

Separately maintained components

Some libraries and tools which used to be part of the OCaml distribution are now maintained separately. Please use the issue trackers at their respective new homes:

• The Graphics library (removed in OCaml 4.09)

• The Num library (removed in OCaml 4.06)

• The OCamlbuild tool (removed in OCaml 4.03)

• The camlp4 tool (removed in OCaml 4.02)

• The LablTk library (removed in OCaml 4.02)

• The CamlDBM library (removed in OCaml 4.00)

• The OCamlWinTop Windows toplevel (removed in OCaml 4.00)

effects-examples's Issues

Add WebServer example

Add the httpaf-based webserver.

Add travis-ci support

Building the examples may break due to upstream changes as seen in #14. So add support for travis-ci to test for these breakages automatically. It appears that the popular way to test OCaml projects is to use ocaml-ci-scripts. The scripts need to be updated to work with the Multicore OCaml compiler.

Investigate CI failure

The CI fails on MacOS with a time out but passes on Linux: https://travis-ci.org/github/ocaml-multicore/effects-examples/builds/747136847

document preferred mechanism to run the examples

problem

• it unclear as to the preferred mechanism on how to run the various included examples

discussion

perhaps steps such as:

• install per link-to-mutlicore-instructions
• run example via ocamlc ...

Migrate the build scripts to dune

Currently we use OCamlbuild. We should port the build system to dune.

Is the secondary compiler necessary now since systhreads work with multicore?

`Yield` effect unused in `aio`

https://github.com/ocaml-multicore/effects-examples/blob/master/aio/aio.ml#L16 defines Yield here, but it's not used anywhere in the rest of the scheduler. Was it supposed to be used somewhere or could we remove it?

(pointed out by @Leonidas-from-XIV)

Errors in building effects-examples

I installed the 5.0.0 today (29 June 2023)

Error 1
Did a make: File "aio/dune", line 3, characters 12-16:
3 | (libraries unix)
^^^^
Error: Library "unix" in /home/doug/.opam/5.0.0/lib/ocaml is hidden
*** fix
In .opam/5.0.0/lib/ocaml
I did: cp unix/unix* .
which fixed this problem

Error 2
Did a make: File "mvar/dune", line 3, characters 24-32:
3 | (libraries threads lwt lwt.unix)
^^^^^^^^
Error: Library "lwt.unix" not found.
*** fix
opam install conduit-lwt-unix

Testing of `promises.ml` seems incomplete

Dear effects examples maintainers,

thanks for the very nice examples on OCaml effects, they are very helpful!

@bhaktishh and I were looking into the promises.ml example, however we have noticed that the way the test are written, it seems that we never call the Wait effect, as all the promises are resolved immediately.

It seems to us that having a more complete test could be useful, what do you think?

We have a few ideas on how to solve this, let us know what do you think?

I guess the first to try would be to decouple promise creation from resolution, but we'd like to hear your opinion before trying to do a pull request.