OCaml Weekly News

I'm happy to announce that Picos version 0.6.0 has been released!

Picos is a systems programming interface between effects based schedulers and concurrent abstractions.

A lot of work has been done on Picos since previous announcements.

You might start on the new minimalist landing page for Picos, which, among other things, allows you to access the documentation of all the released Picos versions.

Also, in case you missed it, a recording of the talk

Picos — Interoperable effects based concurrency

can be found here.

We also held a workshop on concurrency and parallelism at Fun OCaml. You might enjoy trying out the exercise we developed for the workshop.

As, for reasons of dependencies, Picos now comes in no less than 8 packages and multiple libraries, here is a summary of the packages and the libraries inside each package:

• picos — Picos — Interoperable effects based concurrency
  • picos — A systems programming interface between effects based schedulers and concurrent abstractions
  • picos.domain — Minimalistic domain API available both on OCaml 5 and on OCaml 4
  • picos.thread — Minimalistic thread API available with or without threads.posix
• picos_mux — Sample schedulers for Picos
  • picos_mux.fifo — Basic single-threaded effects based Picos compatible scheduler for OCaml 5
  • picos_mux.multififo — Basic multi-threaded effects based Picos compatible scheduler for OCaml 5
  • picos_mux.random — Randomized multi-threaded effects based Picos compatible scheduler for OCaml 5
  • picos_mux.thread — Basic Thread based Picos compatible scheduler for OCaml 4
• picos_std — Sample libraries for Picos
  • picos_std.finally — Syntax for avoiding resource leaks for Picos
  • picos_std.awaitable — Basic futex-like awaitable atomic location for Picos
  • picos_std.event — Basic event abstraction for Picos
  • picos_std.structured — Basic structured concurrency primitives for Picos
  • picos_std.sync — Basic communication and synchronization primitives for Picos
• picos_io — Asynchronous IO system for Picos
  • picos_io — Basic IO facilities based on OCaml standard libraries for Picos
  • picos_io.select — Basic Unix.select based IO event loop for Picos
  • picos_io.fd — Externally reference counted file descriptors
• picos_io_cohttp — Cohttp running on Picos IO
  • picos_io_cohttp — Minimalistic Cohttp implementation using Picos_io for Picos
• picos_lwt — Lwt interface for Picos
  • picos_lwt — Direct style Picos compatible interface to Lwt for OCaml 5
  • picos_lwt.unix — Direct style Picos compatible interface to Lwt with Lwt_unix for OCaml 5
• picos_aux — Auxiliary libraries for Picos
  • picos_aux.htbl — Lock-free hash table
  • picos_aux.mpmcq — Lock-free multi-producer, multi-consumer queue
  • picos_aux.mpscq — Lock-free multi-producer, single-consumer queue
  • picos_aux.rc — External reference counting tables for disposable resources
• picos_meta — Integration tests for Picos packages

In addition to the above, Moonpool now uses Picos underneath.

And, I almost forgot, there is a ready to be merged PR for Kcas to change it to use Picos. You should be able to try it with an opam pin-depends.

findlib-1.9.7 is out. This is mostly a bugfix release. There is now also some support for relocability (driven by environment variables), contributed by Marek Kubica.

For manual, download, manuals, etc. see here:

http://projects.camlcity.org/projects/findlib.html

An updated OPAM package will follow soon.

The release of OCaml version 5.2.1 is imminent.

OCaml 5.2.1 is a collection of safe but import runtime time bug fixes backported from the 5.3 branch of OCaml. The full list of bug fixes is available below.

In order to ensure that the future release works as expected, we are planning to test a release candidate during the upcoming week.

If you find any bugs, please report them here on GitHub.

opam update
opam switch create 5.2.1~rc1

I am pleased to announce the first release of mirage-swapfs (swapfs on opam). It is an experimental library to use a mirage block device for ephemeral, append-only, anonymous "files". It was developed for use cases such as in opam-mirror where opam package source archives are downloaded. The files are first downloaded to "swap" and if the download succeeds and the checksum is as expected the data is then copied over to the tar filesystem.

Internally it uses a weak pointer array (Weak.t) to map "block" offsets to handles. The idea is the garbage collector can help us free up "blocks" if the user forgets to explicitly free the handle. A "block" is (configurable, see blocking_factor) multiple of sectors in order to reduce bookkeeping overhead. With a sector size of 512 bytes the default is 1 MiB per block.

See also the documentation https://robur-coop.github.io/mirage-swapfs/doc/swapfs/index.html

I would be interested to hear about other ideas or approaches.

We will hold our regular Dune dev meeting tomorrow, on Wednesday, November, 13th at 9:00 CET. :warning: Note that the session has been moved one hour earlier. As usual, the session will be one hour long.

Whether you are a maintainer, a regular contributor, a new joiner or just curious, you are welcome to join: these discussions are opened! The goal of these meetings is to provide a place to discuss the ongoing work together and synchronise between the Dune developers !:smile:

Here are links from many OCaml blogs aggregated at the ocaml.org blog.

• Beta release of Frama-C 30.0~beta (Zinc)
• Making OCaml Mainstream: Support Our Open Source Work on GitHub