Class SimpleSelect

  • All Implemented Interfaces:
    Select, java.io.Serializable

    public class SimpleSelect
    extends java.lang.Object
    implements Select
    A simple select implementation based on a two-level inventory, a spill list and broadword bit search.

    This implementation uses around 13.75% additional space on evenly distributed bit arrays, and, under the same conditions, provide very fast selects. For very unevenly distributed arrays the space occupancy will grow significantly, and access time might vary wildly.

    See Also:
    Serialized Form
    Implementation Notes:
    The bulk methods makes it possible to select several consecutive bits at high speed, if the array is reasonably uniform. This is the typical case when this structure is backing an EliasFanoMonotoneLongBigList.
    • Constructor Summary

      Constructors 
      Constructor Description
      SimpleSelect​(long[] bits, long length)
      Creates a new selection structure using a bit vector specified by an array of longs and a number of bits.
      SimpleSelect​(it.unimi.dsi.bits.BitVector bitVector)
      Creates a new selection structure using the specified bit vector.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      it.unimi.dsi.bits.BitVector bitVector()
      Returns the bit vector indexed by this structure.
      long numBits()
      Returns the overall number of bits allocated by this structure.
      long select​(long rank)
      Returns the position of the bit of given rank.
      long[] select​(long rank, long[] dest)
      Performs a bulk select of consecutive ranks into a given array.
      long[] select​(long rank, long[] dest, int offset, int length)
      Performs a bulk select of consecutive ranks into a given array fragment.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • SimpleSelect

        public SimpleSelect​(long[] bits,
                            long length)
        Creates a new selection structure using a bit vector specified by an array of longs and a number of bits.
        Parameters:
        bits - an array of longs representing a bit array.
        length - the number of bits to use from bits.
      • SimpleSelect

        public SimpleSelect​(it.unimi.dsi.bits.BitVector bitVector)
        Creates a new selection structure using the specified bit vector.
        Parameters:
        bitVector - a bit vector.
    • Method Detail

      • select

        public long select​(long rank)
        Description copied from interface: Select
        Returns the position of the bit of given rank. Equivalently, returns the greatest position that is preceded by the specified number of ones.
        Specified by:
        select in interface Select
        Parameters:
        rank - a rank.
        Returns:
        the position of the bit of given rank; if no such bit exists, behavior is undefined .
      • select

        public long[] select​(long rank,
                             long[] dest,
                             int offset,
                             int length)
        Performs a bulk select of consecutive ranks into a given array fragment.
        Specified by:
        select in interface Select
        Parameters:
        rank - the first rank to select.
        dest - the destination array; it will be filled with length positions of consecutive bits starting at position offset; must be of length greater than offset.
        offset - the first bit position written in dest.
        length - the number of bit positions in dest starting at offset.
        Returns:
        dest
        See Also:
        select(long, long[])
        Implementation Notes:
        dest must be of length greater than offset even if length is zero.
      • select

        public long[] select​(long rank,
                             long[] dest)
        Performs a bulk select of consecutive ranks into a given array.
        Specified by:
        select in interface Select
        Parameters:
        rank - the first rank to select.
        dest - the destination array; it will be filled with position of consecutive bits; must be of length greater than zero.
        Returns:
        dest
        See Also:
        select(long, long[], int, int)
        Implementation Notes:
        dest must be of length greater than zero.
      • numBits

        public long numBits()
        Description copied from interface: Select
        Returns the overall number of bits allocated by this structure.
        Specified by:
        numBits in interface Select
        Returns:
        the overall number of bits allocated by this structure (not including the bits of the indexed vector).
      • bitVector

        public it.unimi.dsi.bits.BitVector bitVector()
        Description copied from interface: Select
        Returns the bit vector indexed by this structure.

        Note that you are not supposed to modify the returned vector.

        Specified by:
        bitVector in interface Select
        Returns:
        the bit vector indexed by this structure.