Opam Switch to Multicore OCaml
25 Mar 2015OPAM has a great compiler
switch feature that lets you
simultaneously host several OCaml installations, each with its own compiler
version and a set of installed packages. I wanted to use the power of opam
switch for working with the experimental multicore
OCaml compiler. The key
advantage of doing this is that it lets you easily install packages from the
OPAM repository, while sandboxing it from other OCaml
installations on your system. The post will show how to create OPAM compiler
switch for multicore OCaml.
Install opam-compiler-conf
The first step is to install Gabriel Scherer’s opam-compiler-conf script which lets you do opam switches on local installations:
$ git clone https://github.com/gasche/opam-compiler-conf
$ cd opam-compiler-conf
$ mkdir -p ~/.local/bin
$ make BINDIR=~/.local/bin installThis installs the opam-compiler-conf script under ~/.local/bin. Make sure
this directory is under your search path. Now, $opam compiler-conf should
give you the list of available commands.
Build multicore OCaml locally
Typing opam switch should list the compilers currently installed in your
system and those that are available. For instance, here is my setup:
$ opam switch
system C system System compiler (4.02.1)
4.02.1 I 4.02.1 Official 4.02.1 release
4.02.0 I 4.02.0 Official 4.02.0 release
4.01.0 I 4.01.0 Official 4.01.0 release
-- -- 3.11.2 Official 3.11.2 release
-- -- 3.12.1 Official 3.12.1 release
-- -- 4.00.0 Official 4.00.0 release
-- -- 4.00.1 Official 4.00.1 release
# 66 more patched or experimental compilers, use '--all' to showYou can easily switch between the installations using opam switch
[system-name]. Let us now install multicore OCaml as a new switch:
$ git clone https://github.com/ocamllabs/ocaml-multicore
$ cd ocaml-multicore
$ opam compiler-conf configure
$ make world
$ opam compiler-conf install
$ eval `opam config env`The multicore compiler is now installed and has been made the current compiler:
$ opam switch
system I system System compiler (4.02.1)
4.02.1+local-git-multicore C 4.02.1+local-git-multicore Local checkout of 4.02.1 at /Users/kc/ocaml-multicore
4.02.1 I 4.02.1 Official 4.02.1 release
4.02.0 I 4.02.0 Official 4.02.0 release
4.01.0 I 4.01.0 Official 4.01.0 release
-- -- 3.11.2 Official 3.11.2 release
-- -- 3.12.1 Official 3.12.1 release
-- -- 4.00.0 Official 4.00.0 release
-- -- 4.00.1 Official 4.00.1 release
# 66 more patched or experimental compilers, use '--all' to showThis can be confirmed by:
$ ocamlc -version
4.02.1+multicore-dev0which shows the current OCaml bytecode compiler version.
Working with the local switch
Every time you change the compiler source, you need to rebuild the compiler and reinstall the switch:
# Changed compiler source...
$ make world
$ opam compiler-conf reinstallThe local installation can be removed by opam compiler-conf uninstall.
