OCaml Weekly News

Previous Week Up Next Week


Here is the latest OCaml Weekly News, for the week of May 24 to 31, 2022.

Table of Contents


Danny Willems announced

I'm glad to announce the first (experimental) release of ocaml-carray, a library mocking the Array interface to work with contiguous C array. Disclaimer: this first version is experimental and must be used with caution. A restricted set of values are supported at the moment (custom block with no out-of-heap values). Depending on the demand, more values might be supported. Feel free to use this thread to suggest ideas, make opinions, etc.

Nomadic Labs website
Tezos ZK-rollups repository


OCaml arrays are not always contiguous piece of memory, requiring accessing different chunks of memory when accessing individual elements. When requiring a value in memory, the CPU will fetch the RAM and load not only the particular value but a memory page (a contiguous piece of memory) and add it to its cache. The CPU will use its cache to load the values in its registers. It is not efficient with large OCaml arrays as the CPU will constantly fetch the RAM to load different memory pages in its cache. Also, when using the C FFI, the user must know the memory representation of an array and use the non user-friendly low-level interface macro Field.

This work

This library provides a polymorphic interface mocking a subset of the Array interface to work with contiguous piece of memory. Using the library should be as easy as adding module Array = Carray. A C macro Carray_val is also provided for developers writing bindings and requires to simply cast in the underlying C type. It has also been observed sub arrays are sometimes used for read-only operations. However, Array.sub allocates a fresh copy of the requested sub part. Carray leverages this memory cost by providing noalloc variants, like sub_noalloc.


The concept has been tested and used in real world applications like the polynomial library used by Nomadic Labs to implement zk-rollups. A speed up of around 50% has been observed when using contiguous arrays compared to OCaml arrays to compute NTT/FFT.


This library is experimental. Use this library with caution. The interface might change in the future.

opam install carray.0.0.1

OCaml Users and Developers Workshop 2022

Continuing this thread, Matija Pretnar announced

This is a reminder for anyone interested in contributing to OCaml Workshop 2022. The deadline has been slightly extended to Friday, June 3 (anywhere on Earth), which means you have roughly four days left to prepare your submissions.


If you happen to miss a CWN, you can send me a message and I'll mail it to you, or go take a look at the archive or the RSS feed of the archives.

If you also wish to receive it every week by mail, you may subscribe online.