Hi Abe,
Looks like you just reimplemented SubString.
julia> x = "Hi there!"
"Hi there!"
julia> SubString(x, 2, 4)
"i t"
julia> typeof(ans)
SubString{ASCIIString} (constructor with 1 method)
Which is totally understandable, as there seems to be almost zero
documentation about them. Would you mind opening an issue about that?
Cheers,
Kevin
On Wed, Jun 11, 2014 at 5:08 AM, Abe Schneider <[email protected]>
wrote:
> I'm in the middle of profiling my code, and I noticed that I'm paying a
> penalty for doing a lot of sub-string copies. For what I'm doing, I don't
> actually need copies of the string, but rather just want to keep a pointer
> to the string with the range the view occupies. I thought I'd write up a
> quick test to see if I could speed things up (please ignore the horrible
> names):
>
> import Base: getindex, endof, substring
>
> immutable StringView
> value::String
> first::Int64
> last::Int64
> end
>
> immutable FastString <: String
> value::String
> end
>
> getindex(s::FastString, r::UnitRange{Int64}) = StringView(s.value,
> r.start, r.stop)
> endof(s::FastString) = endof(s.value)
>
>
> const size = 10000000
>
> function teststring()
> s = randstring(size)
> for i=1:size-10
> value = s[i:(i+10)]
> end
> end
>
> function teststringview()
> local s::FastString = FastString(randstring(size))
> for i=1:size-10
> value = s[i:(i+10)]
> end
> end
>
> teststring()
> @time teststring()
>
> teststringview()
> @time teststringview()
>
>
> The results I get are:
> elapsed time: 0.910467582 seconds (890006256 bytes allocated)
> elapsed time: 0.392893967 seconds (409999912 bytes allocated)
>
> The speed-up isn't incredible, but if you're doing a lot of text
> processing, it might help.
>
> I'd be curious if anyone had thoughts or better ways of doing this. Or for
> that matter, reasons why this may be a bad idea.
>
>
