[KPhotoAlbum] Inefficiency in ImageSearchInfo::match()

[Robert Krawitz]

On Tue, 11 Sep 2012 12:53:57 +0200, Jesper K. Pedersen wrote:
> On Sunday 09 September 2012 20:07:34 Robert Krawitz wrote:
>> While coding up the file name match, I noticed that
>> ImageSearchInfo::match() doesn't return as soon as it knows that an
>> image hasn't matched.  There's a lot of code of the form:
>> 
>>     bool ok = true;
>> #ifdef HAVE_EXIV2
>>     ok = _exifSearchInfo.matches( info->fileName() );
>> #endif
>> ...
>>     ok &= ( _label.isEmpty() || info->label().indexOf(_label) != -1 );
>> ...
>>     return ok;
>> 
>> 
>> Is there any reason it does this rather than simply return if any of
>> these tests fail?
>
> I'm 99% sure that &= will not evaluate the right side if the left side
> already is false.
>
> So in effect it does the return right away.

Depends upon just how good the optimizer is.  For example:

    if ( !_date.start().isNull() ) {
        // Date
        // the search date matches the actual date if:
        // actual.start <= search.start <= actuel.end or
        // actual.start <= search.end <=actuel.end or
        // search.start <= actual.start and actual.end <= search.end

        bool b1 =( actualStart <= _date.start() && _date.start() <= actualEnd );
        bool b2 =( actualStart <= _date.end() && _date.end() <= actualEnd );
        bool b3 = ( _date.start() <= actualStart && ( actualEnd <= _date.end() || _date.end().isNull() ) );

        ok &= ( ( b1 || b2 || b3 ) );
    } else if ( !_date.end().isNull() ) {
        bool b1 = ( actualStart <= _date.end() && _date.end() <= actualEnd );
        bool b2 = ( actualEnd <= _date.end() );
        ok &= ( ( b1 || b2 ) );
    }

it would have to look rather deeply at the expressions.  And:

And:

    QString txt = info->description();
    if ( !_description.isEmpty() ) {
        QStringList list = _description.split(QChar::fromLatin1(' '), QString::SkipEmptyParts);
        for( QStringList::Iterator it = list.begin(); it != list.end(); ++it ) {
            ok &= ( txt.indexOf( *it, 0, Qt::CaseInsensitive ) != -1 );
        }
    }

-- 
Robert Krawitz                                     <rlk at alum.mit.edu>

MIT VI-3 1987 - Congratulations MIT Engineers men's hoops Final Four!
Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom  --  http://ProgFree.org
Project lead for Gutenprint   --    http://gimp-print.sourceforge.net

"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton