From what I've read/seen, the go blocks are lightweight thread-like processes multiplexed onto a thread pool. You may be correct about using Thread/sleep, ideally I would have used (timeout ...) and then pulled off the channel. However, I didn't want to introduce the concept of channels too early in the post, so I felt Thread/sleep worked as a compromise.
We will have full API and semantic compatibility when version 0.2 is released next week. Pulsar also has cluster distribution and an Erlang-like actor framework.
Because Pulsar uses instrumentation at the bytecode level, you have more freedom within Go blocks. You wouldn't use Thread/sleep in the Pulsar implementation, either, but Strand/sleep will do the job. It detects whether you're in a go block (implemented as a fiber in Pulsar), in which case it suspends the fiber but doesn't block the thread, or within a normal thread, in which case it will simply call Thread/sleep.
(time (let [c (chan), n 1000] (dotimes [i n] (go (Thread/sleep 50) (>! c i))) (dotimes [i n] (<!! c))))
"Elapsed time: 8412.25733 msecs"
(defmacro gosleep [millis] `(<! (timeout ~millis)))
(time (let [c (chan), n 1000] (dotimes [i n] (go (gosleep 50) (>! c i))) (dotimes [i n] (<!! c))))
"Elapsed time: 91.278469 msecs"
ETA: for comparison, here's what happens if you actually make 1000 system threads:
(time (let [c (chan) n 1000] (dotimes [i n] (thread (Thread/sleep 50) (>!! c i))) (dotimes [i n] (<!! c))))
"Elapsed time: 4183.669835 msecs"
This is an awesome post, thanks for it ^_^