On 17 Nov 2013, at 12:49, Andres Valloud <avall...@smalltalk.comcastbiz.net>
wrote:
> Well, maybe, although it's interesting to consider how many strings streams
> need to beat string concatenation. Moreover, streams aren't hyper efficient
> either…
Yes, indeed. It also depends on what is being concatenated (constants vs
objects).
Quick and dirty (totally unscientific):
[ 'foo', 'bar' ] bench. '4,650,000 per second.'
[ '' join: #( 'foo' 'bar' ) ] bench. '814,000 per second.'
[ String streamContents: [ :out | out nextPutAll: 'foo'; nextPutAll: 'bar' ] ]
bench. '1,900,000 per second.'
[ 'foo', 'bar', 'baz' ] bench. '2,470,000 per second.'
[ '' join: #( 'foo' 'bar' 'baz' ) ] bench. '719,000 per second.'
[ String streamContents: [ :out | out nextPutAll: 'foo'; nextPutAll: 'bar';
nextPutAll: 'baz' ] ] bench. '1,710,000 per second.'
[ 'foo', 'bar', 'baz', 'foobar' ] bench. '2,030,000 per second.'
[ '' join: #( 'foo' 'bar' 'baz' 'foobar' ) ] bench. '665,000 per second.'
[ String streamContents: [ :out | out nextPutAll: 'foo'; nextPutAll: 'bar';
nextPutAll: 'baz'; nextPutAll: 'foobar' ] ] bench. '1,580,000 per second.'
[ Date today asString, $- asString, Time now asString ] bench. '61,800 per
second.'
[ String streamContents: [ :out | out print: Date today; nextPut: $-; print:
Time now ] ] bench. '71,700 per second.'
We’re only measuring execution speed, not memory allocation, which is important
too.
The length of the strings is a variable as well, of course.
Furthermore, many #printOn: implementations are not very efficient while they
should be.
Conclusion, let’s be careful with a too simple advice.
Sven
> On 11/16/13 10:09 , b...@openinworld.com wrote:
>>
>> Code Critic rule Optimization > String concatenation instead of streams
>> says:
>>
>> "Check for string concatenation inside some iteration message. Since
>> string concatenation is O(n^2), it is better to use streaming since it
>> is O(n) - assuming that n is large enough. As a general principal avoid
>> , since the receiver is copied. Therefore chaining , messages will lead
>> to multiple useless copies of the receiver."
>>
>> That is,
>> String streamContents: [:s |
>> #('abc' 'def' 'ghi') do: [:each | s nextPutAll: each asString]]
>>
>> should be used instead of...
>> 'abc' , 'def' , 'ghi'.
>>
>> However the first clutters the code. What about something like...
>> { 'abc' . 'def' . 'ghi' } asStreamString
>> where
>> Collection>>asStreamString
>> ^ String streamContents: [:s | self do: [:each | s nextPutAll:
>> each asString]]
>>
>> cheers -ben
>>
>
