On Tue, Jul 21, 2015 at 7:08 PM, Jameson Nash <vtjn...@gmail.com> wrote:
> does `copy` work? although `bytestring` also seems like a good method for
> this also. it seems wrong to me also that `match` is making a copy of the
> original string (if that is indeed what it is doing)
Isn't it `s[i:end]` that is doing the copy?
>
> On Tue, Jul 21, 2015 at 6:57 PM andrew cooke <and...@acooke.org> wrote:
>>
>>
>> string(bytestring(...)) seems to do it. would appreciate any more
>> efficient solutions (and confirmation the analysis is correct - is this
>> worth filing as an issue?)
>>
>>
>> On Tuesday, 21 July 2015 19:33:05 UTC-3, andrew cooke wrote:
>>>
>>>
>>> well, this was fun... the following code rapidly triggers the OOM killer
>>> on my machine (julia 0.4 trunk):
>>>
>>> s = repeat("a", 1000000)
>>> l = Any[]
>>> r = r"^\w"
>>>
>>> for i in 1:length(s)
>>> m = match(r, s[i:end])
>>> push!(l, m.match)
>>> end
>>>
>>> note that: (1) the regexp is only matching one character, so the array l
>>> is at most a million characters long.
>>>
>>> what i think is happening (but this is only a guess) is that s[i:end] is
>>> being passed though to the c level regexp library as a new string. the
>>> result (m.match) is then a substring into that. because the substring is
>>> kept around, the backing string cannot be collected. and so there's an n^2
>>> memory use.
>>>
>>> ideally, i don't think a new copy of the string should be passed to the
>>> regexp engine. maybe i am wrong?
>>>
>>> anyway, for now, if the above is right, i need some way to copy m.match.
>>> as far as i can tell string() doesn't help. so what works? or am i wrong?
>>>
>>> thanks,
>>> andrew
