Question

In my project many clients will modify a map in server. I use a ref of map, like this:

(def dict (ref {})) ; the map we play with

And I update this map using dosync, the STM way. But I found it not as fast as I wish:

user=> (time (dotimes [n 1000000] (dosync ( alter xx assoc xx 1 1))))
"Elapsed time: 2470.766 msecs"

So I decide to use native Java CuncurrentHashMap to take the place of Clojure build-in map and STM. How can I wrap Java CuncurrentHashMap into Clojure so that i can modify it like Clojure map, using assoc, contains?, dissoc and so on. This will make me modify lest line of code.

Is there a way to achieve this?

Answer 1

You can use atom, as you are only modifying a single value you don’t need a transaction and hence no need for ref

user=> (def dict (atom {}))
user=> (time (dotimes [n 1000000] (swap! dict assoc :xx 1)))
"Elapsed time: 108.105703 msecs"