Hi Max,
Interesting results...
replacing the #yourself in newSum: cuts the runtime by a factor of two.
using an [:x | x ] block cost 10% compared to a direct version of sum.
So the fastest sum is:
sum
^ self
inject:
(self ifEmpty: [ ^ 0 ] ifNotEmpty: [ self anyOne ])
into: [ :sum :each | sum + each ]
And
sum
^ self sum: [:x | x ]
is 10% slower.
And
sum
^ self sum: #yourself
is 100% slower (i.e. x2)
It may be wise to avoid using #yourself for a block.
Thierry
2015-12-01 9:17 GMT+01:00 Max Leske <[email protected]>:
> Hi guys,
>
> Collection defines #sum:, #detectSum: and #sumNumbers:, all of which
> accomplish the same (in principal) but with subtle differences:
>
> #sum:
> - uses #inject:into: with #anyOne as the injected element and will thus
> fail for empty collections
>
> #detectSum:
> - uses “nextValue + sum” instead of “sum + nextValue” which makes it a lot
> slower when dealing with large numbers (primitive fails and number
> conversion is necessary)
>
> #sumNumbers:
> - same as #sum but doesn’t fail for empty collections. Only good for
> numbers though.
>
>
> Benchmarks:
>
> [ 100 timesRepeat: [ (1 to: 1000000) sum: #yourself ] ] timeToRun 18062
> [ 100 timesRepeat: [ (1 to: 1000000) detectSum: #yourself ] ] timeToRun
> 42391
> [ 100 timesRepeat: [ (1 to: 1000000) sumNumbers: #yourself ] ] timeToRun
> 18096
>
>
>
> Can we settle for a single implementation? Such as (modified from
> #sumNumbers:):
>
> newSum: aBlock
> ^ self
> inject: (self
> ifEmpty: [ 0 ]
> ifNotEmpty: [ self anyOne ])
> into: [ :sum :each | sum + (aBlock value: each) ]
>
> This implementation combines the best of the three implementations I
> think. Benchmark:
>
> [ 100 timesRepeat: [ (1 to: 1000000) newSum: #yourself ] ] timeToRun 17955
>
>
> BTW, there is also the message #sum, which suffers from the same problem
> as #sum: (the implementation is basically a copy). #sum could be
> implemented as
>
> sum
> ^ self sum: [ :x | x ]
>
>
> As for the name for the new method, I suggest #sum:.
>
> Cheers,
> Max
>
