2021/04/18

Two concurrency utilities

Since I haven't written this blog for a while, it's a good time to catch up recent changes in Gauche HEAD.

Lately, we added a couple of utility modules that help to write concurrent programs.

control.future (draft:control.future) - A typical future, that is, evaluate the given expression in a separate thread concurrently. The result can be retrieved with future-get.

(use control.future)
(use rfc.http)

(let1 f (future (http-get "example.com" "/"))
  ... some computation ...
  (receive (code headers body) (future-get f)
    ...))

Like most of other synchronization operations in Gauche, future-get can take timeout parameter.

control.cseq (draft:control.cseq) - It's a lazy sequence but the data generator runs in a separate thread. It can abstract producer-consumer type concurrency.

The same concurrency can be achieved with <mtqueue> (ref:data.queue), and in fact control.cseq uses mtqeuee internally, but cseq is characteristic that you can very easily change lazy sequence code into concurrent code.

(generator->lseq gen) returns an lseq, which looks like an ordinary list, but when you walk down its cdr, the generator gen is called to generate more items.

(generator->cseq gen) also returns an lseq. But in this case, gen runs concurrently in a separate thread. In many cases, you can simply replace lseq to cseq to get the benefit of concurrency.

The module also provides coroutine->cseq, which uses coroutine to generate the items, run in a separate thread.

Tags: 0.9.11, Concurrency