> On 01 Dec 2015, at 10:24, Thierry Goubier <[email protected]> wrote: > > Note that the sum with #anyOne is wrong. > > #(1 2 3 4 5) inject: #(1 2 3 4 5) anyOne into: [ :sum :each | sum + each ] > > returns 16 instead of 15.
You have subtract the element you picked with #anyOne ! > Thierry > > 2015-12-01 10:18 GMT+01:00 Ben Coman <[email protected]>: > On Tue, Dec 1, 2015 at 4:45 PM, Sven Van Caekenberghe <[email protected]> wrote: > > I am all for a cleanup, the current situation is confusing. > > The basic #sum should be fast AND work for empty collections with 0 as > > starting element. > > > I know why the #anyOne is used, and that use case should be preserved, but > > it is less common IMHO. > > I'm curious to be learn why? > cheers -ben > > > > >> On 01 Dec 2015, at 09:38, Thierry Goubier <[email protected]> > >> wrote: > >> > >> 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 > >> > > > > > >
