title: Fastest way to select objects using other collection in Smalltalk
body: <p>Given two collections:</p>
  
  <pre><code>srcCollection := #('Lorem' 'ipsum' 'dolor' 'sit' 'amet,' 'consectetur' 'adipisicing' 'elit,' 'sed' 'do' 'eiusmod' 'tempor' 'incididunt' 'ut' 'labore' 'et' 'dolore' 'magna' 'aliqua.' 'Ut' 'enim' 'ad' 'minim' 'veniam,' 'quis' 'nostrud' 'exercitation' 'ullamco' 'laboris' 'nisi' 'ut' 'aliquip' 'ex' 'ea' 'commodo' 'consequat.' 'Duis' 'aute' 'irure' 'dolor' 'in' 'reprehenderit' 'in' 'voluptate' 'velit' 'esse' 'cillum' 'dolore' 'eu' 'fugiat' 'nulla' 'pariatur.' 'Excepteur' 'sint' 'occaecat' 'cupidatat' 'non' 'proident,' 'sunt' 'in' 'culpa' 'qui' 'officia' 'deserunt' 'mollit' 'anim' 'id' 'est' 'laborum').      
  objCollection := #('Lorem' 'numquam' 'eius' 'modi' 'tempora' 'incidunt' 'ut' 'labore' 'et' 'dolore' 'magnam' 'aliquam' 'ipsum' 'dolor' 'ex' 'ea' 'commodo' 'consequat.' 'Duis' 'aute' 'irure' 'dolor' 'in' 'reprehenderit' 'in' 'voluptate' 'velit' 'esse' 'cillum' 'dolore' 'eu' 'fugiat' 'nulla' 'pariatur.' 'Excepteur' 'sint' 'occaecat' 'cupidatat' 'non' 'proident,' 'sunt' 'in' 'culpa' 'qui' 'officia' 'deserunt' 'mollit' 'anim' 'id' 'est' 'laborum' 'Sed' 'ut' 'perspiciatis' 'unde' 'omnis' 'iste' 'natus' 'error' 'sit' 'voluptatem' 'accusantium' 'doloremque' 'laudantium,' 'totam' 'rem' 'aperiam,' 'eaque' 'ipsa' 'quae' 'ab' 'illo' 'inventore' 'veritatis' 'et' 'quasi' 'architecto' 'sit' 'amet,' 'consectetur' 'adipisicing' 'elit,' 'sed' 'do' 'eiusmod' 'tempor' 'incididunt' 'ut' 'labore' 'et' 'dolore' 'magna' 'aliqua.' 'Ut' 'enim' 'ad' 'minim' 'veniam,' 'quis' 'nostrud' 'exercitation' 'ullamco' 'laboris' 'nisi' 'ut' 'aliquip' 'beatae' 'vitae' 'dicta' 'sunt' 'explicabo.' 'Nemo' 'enim' 'ipsam' 'voluptatem' 'quia' 'voluptas' 'sit' 'aspernatur' 'aut' 'odit' 'aut' 'fugit,' 'sed' 'quia' 'consequuntur' 'magni' 'dolores' 'eos' 'qui' 'ratione' 'voluptatem' 'sequi' 'nesciunt.' 'Neque' 'porro' 'quisquam' 'est,' 'qui' 'dolorem' 'ipsum' 'quia' 'dolor' 'sit' 'amet,' 'consectetur,' 'adipisci' 'velit,' 'sed' 'quia' 'non' 'quaerat' 'voluptatem.' 'Ut' 'enim' 'ad' 'minima' 'veniam,' 'quis' 'nostrum' 'exercitationem' 'ullam' 'corporis' 'suscipit' 'laboriosam,' 'nisi' 'ut' 'aliquid' 'ex' 'ea' 'commodi' 'consequatur?' 'Quis' 'autem' 'vel' 'eum' 'iure' 'reprehenderit' 'qui' 'in' 'ea' 'voluptate' 'velit' 'esse' 'quam' 'nihil' 'molestiae' 'consequatur,' 'vel' 'illum' 'qui' 'dolorem' 'eum' 'fugiat' 'quo' 'voluptas' 'nulla' 'pariatur?').
  </code></pre>
  
  <p>where objCollection is guaranteed to contain all elements in srcCollection. Note: In my application objCollection are actually complex objects containing these strings as identifiers with no duplicates.</p>
  
  <p>I've been measuring and trying to optimize selecting all the objects in objCollection that are also in srcCollection. The times below are in milliseconds using <code>[ 1000 timesRepeat: [ ... ] ] timeToRun</code> in Pharo 1.2 with Stack VM and Windows XP with 2Gb of memory. These are my attempts:</p>
  
  <pre><code>objCollection intersection: srcCollection
  7537
  7507
  
  objCollection select: [: str | srcCollection includes: str ]
  7471
  7507
  
  srcCollection collect: [: str | objCollection detect: [: obj | obj = str ] ]
  4227
  4323
  </code></pre>
  
  <p>Is there a faster way?</p>