MinMaxNumberList
cern.colt.list

Class MinMaxNumberList

  • All Implemented Interfaces:
    Serializable, Cloneable


    public class MinMaxNumberListextends AbstractLongList
    Resizable compressed list holding numbers; based on the fact that a value in a given interval need not take more than log(max-min+1) bits; implemented with a cern.colt.bitvector.BitVector. First see the package summary and javadoc tree view to get the broad picture.

    Numbers can be compressed when minimum and maximum of all values ever to be stored in the list are known. For example, if min=16, max=27, only 4 bits are needed to store a value. No compression is achieved for float and double values.

    You can add, get and set elements quite similar to java.util.ArrayList.

    Applicability: Applicable if the data is non floating point, highly skewed without "outliers" and minimum and maximum known in advance.

    Performance: Basic operations like add(), get(), set(), size() and clear() are O(1), i.e. run in constant time.

    200Mhz Pentium Pro, JDK 1.2, NT:
    10^6 calls to getQuick() --> 0.5 seconds. (50 times slower than reading from a primitive array of the appropriate type.)
    10^6 calls to setQuick() --> 0.8 seconds. (15 times slower than writing to a primitive array of the appropriate type.)

    This class can, for example, be useful when making large lists of numbers persistent. Also useful when very large lists would otherwise consume too much main memory.

    Upon instantiation a contract is signed that defines the interval values may fall into. It is not legal to store values not contained in that interval. WARNING: The contract is not checked. Be sure you do not store illegal values. If you need to store float or double values, you must set the minimum and maximum to [Integer.MIN_VALUE,Integer.MAX_VALUE] or [Long.MIN_VALUE,Long.MAX_VALUE], respectively.

    Although access methods are only defined on long values you can also store all other primitive data types: boolean, byte, short, int, long, float, double and char. You can do this by explicitly representing them as long values. Use casts for discrete data types. Use the methods of java.lang.Float and java.lang.Double for floating point data types: Recall that with those methods you can convert any floating point value to a long value and back without losing any precision:

    Example usage:

     MinMaxNumberList list = ... instantiation goes here double d1 = 1.234; list.add(Double.doubleToLongBits(d1)); double d2 = Double.longBitsToDouble(list.get(0)); if (d1!=d2) System.out.println("This is impossible!"); MinMaxNumberList list2 = ... instantiation goes here float f1 = 1.234f; list2.add((long) Float.floatToIntBits(f1)); float f2 = Float.intBitsToFloat((int)list2.get(0)); if (f1!=f2) System.out.println("This is impossible!"); 
    See Also:
    LongArrayList, DistinctNumberList, Float, Double, Serialized Form
    • Constructor Detail

      • MinMaxNumberList

        public MinMaxNumberList(long minimum,                long maximum,                int initialCapacity)
        Constructs an empty list with the specified initial capacity and the specified range of values allowed to be hold in this list. Legal values are in the range [minimum,maximum], all inclusive.
        Parameters:
        minimum - the minimum of values allowed to be hold in this list.
        maximum - the maximum of values allowed to be hold in this list.
        initialCapacity - the number of elements the receiver can hold without auto-expanding itself by allocating new internal memory.
    • Method Detail

      • add

        public void add(long element)
        Appends the specified element to the end of this list.
        Overrides:
        add in class AbstractLongList
        Parameters:
        element - element to be appended to this list.
      • addAllOfFromTo

        public void addAllOfFromTo(long[] elements,                  int from,                  int to)
        Appends the elements elements[from] (inclusive), ..., elements[to] (inclusive) to the receiver.
        Parameters:
        elements - the elements to be appended to the receiver.
        from - the index of the first element to be appended (inclusive)
        to - the index of the last element to be appended (inclusive)
      • bitsPerElement

        public int bitsPerElement()
        Returns the number of bits necessary to store a single element.
      • bitsPerElement

        public static int bitsPerElement(long minimum,                 long maximum)
        Returns the number of bits necessary to store values in the range [minimum,maximum].
      • ensureCapacity

        public void ensureCapacity(int minCapacity)
        Ensures that the receiver can hold at least the specified number of elements without needing to allocate new internal memory. If necessary, allocates new internal memory and increases the capacity of the receiver.
        Specified by:
        ensureCapacity in class AbstractLongList
        Parameters:
        minCapacity - the desired minimum capacity.
      • getQuick

        public long getQuick(int index)
        Returns the element at the specified position in the receiver; WARNING: Does not check preconditions. Provided with invalid parameters this method may return invalid elements without throwing any exception! You should only use this method when you are absolutely sure that the index is within bounds. Precondition (unchecked): index >= 0 && index < size().
        Parameters:
        index - index of element to return.
      • partFromTo

        public void partFromTo(int from,              int to,              BitVector qualificants,              int qualificantsFrom,              long[] part,              int partFrom)
        Copies all elements between index from (inclusive) and to (inclusive) into part, starting at index partFrom within part. Elements are only copied if a corresponding flag within qualificants is set. More precisely:
         for (; from<=to; from++, partFrom++, qualificantsFrom++) {    if (qualificants==null || qualificants.get(qualificantsFrom)) {       part[partFrom] = this.get(from);    } } 
      • setQuick

        public void setQuick(int index,            long element)
        Replaces the element at the specified position in the receiver with the specified element; WARNING: Does not check preconditions. Provided with invalid parameters this method may access invalid indexes without throwing any exception! You should only use this method when you are absolutely sure that the index is within bounds. Precondition (unchecked): index >= 0 && index < size().
        Parameters:
        index - index of element to replace.
        element - element to be stored at the specified position.
      • toBitVector

        public BitVector toBitVector()
        Returns the receiver seen as bitvector. WARNING: The bitvector and the receiver share the backing bits. Modifying one of them will affect the other.
      • trimToSize

        public void trimToSize()
        Trims the capacity of the receiver to be the receiver's current size. An application can use this operation to minimize the storage of the receiver.
        Overrides:
        trimToSize in class AbstractList
      • xminimum

        public long xminimum()
        Deprecated. 
        deprecated Returns the minimum element legal to the stored in the receiver. Remark: This does not mean that such a minimum element is currently contained in the receiver.

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