Chris Vine <[email protected]> writes:
> On Fri, 26 May 2017 12:37:47 +0200
> [email protected] wrote:
>> Hello,
>>
>> I'm making a simple program that processes a lot of mail in separate
>> guile threads.
>>
>> I would like a counter of how many messages have been processed so I
>> made an attempt with atomics.
>>
>> first:
>> (define *msgcount* (make-atomic-box 0))
>>
>> and later:
>> (atomic-box-swap! *msgcount* (+ 1 (atomic-box-ref *msgcount*)))
>>
>> This of course doesn't work very well, and I didnt expect it to
>> either. (usually the count is low by a couple of hundred messages)
>>
>> So basically, how do I get something similar to the swap! function in
>> clojure? Did I miss something in the documentation for guiles atomics?
>>
>> I think I expected to be able to do the following:
>> (atomic-box-swap! *msgcount* (lambda (atom) (+ 1 (atomic-box-ref
>> atom))))
>
> That won't work. You have to use atomic-box-compare-and-swap!, in order
> to detect interleaving by other threads. For more on this, google
> "compare and swap".
I wound up with this, is there some better way to do this? Feels a bit verbose.
(define (incatom atom)
(let ((expected (atomic-box-ref atom)))
(while (not (= expected (atomic-box-compare-and-swap! atom expected (+ 1
expected))))
(set! expected (atomic-box-ref atom)
))))
>
>
>
--
Joakim Verona
[email protected]
