-*- mode: org -*-
Fork-future is a posix fork() based future parallel library (forked from cl-future)
by Jianshi Huang @ Mathematical Systems Inc. (huang@msi.co.jp)
Fork() based parallelism has the merit that it makes mutual exclusion unnecessary since each process has its own memory space. Second, The copy-on-write semantics of memory management is also convenient for concurrency which doesn’t need synchronization. In other words, the OS will help us manage the resource for sharing data and isolating the execution context.
There is a similar library by Jeff Palmucci called cl-future (http://github.com/jpalmucci/cl-future). fork-future is a fork of cl-future and they share same implementation ideas.
The reason to fork it is:
- simplifying the implementation
- better APIs and documentations
You can almost guess the meaning just by looking at the function name. Also borrow the API from PLT-scheme’s future library, which is ‘future’ and ‘touch’.
- thorough testing
Since it will be used in our commercial products, tests are very important. Tests on multiple implementations and stress tests are very important for us.
| SBCL | AllegroCL | Lispworks | ClozureCL | |
|---|---|---|---|---|
| Linux-x86 | Yes | Yes | Untested | Yes |
| Linux-x8664 | Yes | Yes | Untested | Yes |
Fork-future depends on cl-store, cffi and cl-containers. In the future releases, I may remove the dependency of cl-containers.
Tests depends on Stefil test framework.
The followings are public APIs:
future touch wait-for-future wait-for-any-future wait-for-all-futures kill-future kill-all-futures initialize-environment with-new-environment before-fork-hooks after-fork-hooks future-result-file-template fork-future-max-processes
- future : Macro
(future &body body) is used to create a future object that evaluates the body.
- touch : Function
(touch future) is to obtain the evaluation result of the future, it will block if the future is not finished yet.
- initialize-environment : Function
(initialize-environment &key kill-current-futures-p force-p) will clean up the environment which is essential for the precondition of later futures to run properly.
It is strongly suggested to call initialize-environment before starting a paralleled task.
- with-new-environment : Macro
(with-new-environment () &body body) will create new environments and process pools that does not interfere current running and pending futures.
A common practice is to write the following code:
(with-new-environment () …body)
in new paralleled tasks. with-new-environment will insert initialize-environment before body.
:fork-future will be pushed to features after loading.