Quoting Eliot Miranda <eliot.miranda at gmail.com>:

> Hi Phillipe,
>
>
>     On Mon, May 26, 2014 at 12:51 AM, Philippe Marschall
> <philippe.marschall at netcetera.ch> wrote:
>
>> Hi
>>
>> I have been investigating why Dictionary look up performance with
>> String keys is not as good as I would expected. Something I noted is
>> that String >> #= is implemented in terms of #compare:with:collated:.
>> There is no short circuit if Strings are not the same size. In my case
>> some Strings have the same prefix but a different length eg
>> 'Content-Type' and 'Content-Length'. In that case a
>> #compare:with:collated: is performed even though we know in advance the
>> answer will be false because they have different sizes.
>
>       
>      Why not rewrite
>       
>      String>>= aString 
>      "Answer whether the receiver sorts equally as aString.
>      The collation order is simple ascii (with case differences)."
>      aString isString ifFalse: [ ^ false ].
>      ^ (self compare: self with: aString collated: AsciiOrder) = 2
>       
>      as
>       
>            String>>= aString 
>       "Answer whether the receiver sorts equally as aString.
>       The collation order is simple ascii (with case differences)."
>        
>       (aString isString
>       and: [self size = aString size]) ifFalse: [^false].
>       ^ (self compare: self withSize: with: aString collated:
> AsciiOrder) = 2
>
>       
>      ?
>
>      
> One /could/ add a replacement compare:with:collated:
> primitive primitiveCompareString which took the sizes as arguments to
> avoid asking twice.  But it wouldn't be safe.  One could abuse the
> primitive and lie about the size.  So I suspect it is best to add the
> size check to String>>#= and accept the duplication of
> the primitive finding the sizes of the two strings.  The cost in the
> primitive is minimal.  A WideString version of the primitive might pay
> its way, but if Spur and Sista arrive soon the primitive shouldn't be
> faster than the optimised Smalltalk code.
> --
> best,        Eliot

BTW, any good reason for not prefixing all the implementors of #= with
this?

"Any object is equal to itself"
self == argument ifTrue: [ ^ true ].
Cheers,
Juan Vuletich
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.squeakfoundation.org/pipermail/squeak-dev/attachments/20140527/ac637289/attachment.htm