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. Thierry 2015-12-01 10:18 GMT+01:00 Ben Coman <btc@openinworld.com>:
On Tue, Dec 1, 2015 at 4:45 PM, Sven Van Caekenberghe <sven@stfx.eu> 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 <thierry.goubier@gmail.com>
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 <maxleske@gmail.com>: 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 ânextValue + sumâ instead of âsum + nextValueâ which makes it a
lot slower when dealing with large numbers (primitive fails and number conversion is necessary)
#sumNumbers: - same as #sum but doesnât 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