Package it.unimi.dsi.sux4j.mph

Class HollowTrieDistributor<T>

java.lang.Object
it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction<T>
it.unimi.dsi.sux4j.mph.HollowTrieDistributor<T>
All Implemented Interfaces:
Function<T,Long>, Object2LongFunction<T>, Size64, Serializable, Function<T,Long>, ToLongFunction<T>
public class HollowTrieDistributor<T> extends AbstractObject2LongFunction<T> implements Size64
A distributor based on a hollow trie.

Implementation details

This class implements a distributor on top of a hollow trie. First, a compacted trie is built from the delimiter set. Then, for each key we compute the node of the trie in which the bucket of the key is established. This gives us, for each node of the trie, a set of paths to which we must associate an action (exit on the left, go through, exit on the right). Overall, the number of such paths is equal to the number of keys plus the number of delimiters, so the mapping from each pair node/path to the respective action takes linear space. Now, from the compacted trie we just retain a hollow trie, as the path-length information is sufficient to rebuild the keys of the above mapping. By sizing the bucket size around the logarithm of the average length, we obtain a distributor that occupies linear space.

See Also:

  • Field Details

    • meanSkipLength

      protected double meanSkipLength
      The average skip length in bits (actually, the average length in bits of a skip length increased by one).

  • Constructor Details

    • HollowTrieDistributor

      public HollowTrieDistributor(Iterable<? extends T> elements, int log2BucketSize, TransformationStrategy<? super T> transformationStrategy) throws IOException
      Creates a partial compacted trie using given elements, bucket size and transformation strategy.
      Parameters:
      elements - the elements among which the trie must be able to rank.
      log2BucketSize - the logarithm of the size of a bucket.
      transformationStrategy - a transformation strategy that must turn the elements in elements into a list of distinct, lexicographically increasing (in iteration order) bit vectors.
      Throws:
      IOException

    • HollowTrieDistributor

      public HollowTrieDistributor(Iterable<? extends T> elements, int log2BucketSize, TransformationStrategy<? super T> transformationStrategy, File tempDir) throws IOException
      Creates a hollow trie distributor.
      Parameters:
      elements - the elements among which the trie must be able to rank.
      log2BucketSize - the logarithm of the size of a bucket.
      transformationStrategy - a transformation strategy that must turn the elements in elements into a list of distinct, lexicographically increasing (in iteration order) bit vectors.
      tempDir - the directory where temporary files will be created, or for the default directory.
      Throws:
      IOException

  • Method Details