Atomic Integer incr/decr
Ruby does not any thread-safe way to implement simple counters without a Mutex. Today Ruby provides Integer#succ but this funcalls "+", making it thread-unsafe as far as I know.
I'd propose adding Integer#incr(amount=1) and Integer#reset which would use atomic operations, giving us thread-safe, high-performance counters.
counter = 0 counter.incr # => 1 counter.incr(10) # => 11 counter.incr(-1) # => 10 counter.reset # => 10 counter # => 0
Updated by jeremyevans0 (Jeremy Evans) almost 3 years ago
I think this feature in general is a good candidate for addition to stdlib.
I don't think the
Integer class is appropriate for this, because (some) Integers are immediate values, and all Integers are frozen, and you can't modify them.
Integer#succ are thread safe (they return new objects, they do not modify existing objects), it's
counter += 1 that is not thread safe.
In terms of naming, maybe
Integer::Counter since that is unlikely to conflict with existing code, with an API like:
counter = Integer::Counter.new(0) # maybe default to 0 if no argument? counter.incr # => 1 counter.incr(10) # => 11 counter.incr(-1) # => 10 counter.reset # => 10 counter.to_int # => 0 counter.to_i # => 0
Updated by mperham (Mike Perham) almost 3 years ago
Jeremy, good point. I would agree that the different semantics are enough to justify a different class. Namespacing it within the Thread class also seems reasonable, e.g.
Thread::Counter so it would be available if you
Updated by shevegen (Robert A. Heiler) almost 3 years ago
I guess this may come up several times in the future. Would
this be a good candidate for discussion in the upcoming
ruby developer meeting? I don't want to suggest it myself
since I was not the one who started the thread (that was
Mike), but it seems to come up every now and then by
different people, so it may be of some relevance.
Rafael França pointed out that it was parially rejected/closed
but I think that did not come via matz primarily since he
did not comment on it; it may be that other ruby developers
pointed out some problems with it before, like Koichi; but
it may still be good to have matz comment on it so that
people can understand what the remaining problems may be,
if there are some.