The threads library

The threads library

The threads library allows concurrent programming in Objective Caml. It provides multiple threads of control (also called lightweight processes) that execute concurrently in the same memory space. Threads communicate by in-place modification of shared data structures, or by sending and receiving data on communication channels.

The threads library is implemented by time-sharing on a single processor. It will not take advantage of multi-processor machines. Using this library will therefore never make programs run faster. However, many programs are easier to write when structured as several communicating processes.

Unix:

Programs that use the threads library must be linked as follows:
        ocamlc -thread other options threads.cma other files
The -thread option selects a special, thread-safe version of the standard library (see chapter 8). The -thread option must also be given when compiling any source file that references modules from the thread library (Thread, Mutex, ...).

The default thread implementation cannot be used in native-code programs compiled with ocamlopt. If your operating system provides POSIX 1003.1c compliant threads, you can select an alternate implementation when configuring Objective Caml (use the -with-pthread option to configure) which also supports native-code programs. Programs that use this alternate implementation of the threads library must be linked as follows:
        ocamlc -thread other options threads.cma other files
        ocamlopt -thread other options threads.cmxa other files
Depending on the operating system, extra system libraries can be necessary. For instance, under Solaris 2.5, add -cclib -lposix4 at the end of the command line.

Windows:

Programs that use the threads library must be linked as follows:
        ocamlc -thread other options threads.cma other files
All object files on the command line must also have been compiled with the -thread option, which selects a special, thread-safe version of the standard library (see chapter 8).