org.apache.datasketches

Enum InequalitySearch

java.lang.Object

java.lang.Enum<InequalitySearch>

org.apache.datasketches.InequalitySearch

All Implemented Interfaces:

Serializable, Comparable<InequalitySearch>

public enum InequalitySearch
extends Enum<InequalitySearch>

This provides efficient, unique and unambiguous binary searching for inequality comparison criteria for ordered arrays of values that may include duplicate values. The inequality criteria include <, ≤, ==, ≥, >. All the inequality criteria use the same search algorithm. (Although == is not an inequality, it is included for convenience.)

In order to make the searching unique and unambiguous, we modified the traditional binary search algorithm to search for adjacent pairs of values {A, B} in the values array instead of just a single value, where A and B are the array indices of two adjacent values in the array. For all the search criteria, if the algorithm reaches the ends of the search range, the algorithm calls the resolve() method to determine what to return to the caller. If the key value cannot be resolved, it returns a -1 to the caller.

Given a sorted array of values arr[] and the search key value v, the algorithms for the searching criteria are given with each enum criterion.

Author:

Lee Rhodes

Enum Constant Summary

Enum Constants

Enum Constant and Description
EQ Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the adjacent pair of values {A,B} such that A ≤ V ≤ B.
GE Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the lowest adjacent pair of values {A,B} such that A < V ≤ B. Let low = lowest index of the lowest value in the range. Let high = highest index of the highest value in the range.
GT Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the lowest adjacent pair of values {A,B} such that A ≤ V < B. Let low = lowest index of the lowest value in the range. Let high = highest index of the highest value in the range.
LE Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the highest adjacent pair of values {A,B} such that A ≤ V < B. Let low = lowest index of the lowest value in the range. Let high = highest index of the highest value in the range.
LT Given a sorted array of increasing values arr[] and a key value v, this criterion instructs the binary search algorithm to find the highest adjacent pair of values {A,B} such that A < v ≤ B. Let low = lowest index of the lowest value in the range. Let high = highest index of the highest value in the range.

Method Summary

Modifier and Type	Method and Description
static int	find(double[] arr, int low, int high, double v, InequalitySearch crit) Binary Search for the index of the double value in the given search range that satisfies the given InequalitySearch criterion.
static int	find(float[] arr, int low, int high, float v, InequalitySearch crit) Binary Search for the index of the float value in the given search range that satisfies the given InequalitySearch criterion.
static int	find(long[] arr, int low, int high, long v, InequalitySearch crit) Binary Search for the index of the long value in the given search range that satisfies the given InequalitySearch criterion.
static InequalitySearch	valueOf(String name) Returns the enum constant of this type with the specified name.
static InequalitySearch[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

LT

public static final InequalitySearch LT

Given a sorted array of increasing values arr[] and a key value v, this criterion instructs the binary search algorithm to find the highest adjacent pair of values {A,B} such that A < v ≤ B.
Let low = lowest index of the lowest value in the range.
Let high = highest index of the highest value in the range.

If v > arr[high], return arr[high].
If v ≤ arr[low], return -1.
Else return index of A.

LE

public static final InequalitySearch LE

Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the highest adjacent pair of values {A,B} such that A ≤ V < B.
Let low = lowest index of the lowest value in the range.
Let high = highest index of the highest value in the range.

If v ≥ arr[high], return arr[high].
If v < arr[low], return -1.
Else return index of A.

EQ

public static final InequalitySearch EQ

Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the adjacent pair of values {A,B} such that A ≤ V ≤ B. The returned value from the binary search algorithm will be the index of A or B, if one of them is equal to V, or -1 if V is not equal to either one.

GE

public static final InequalitySearch GE

Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the lowest adjacent pair of values {A,B} such that A < V ≤ B.
Let low = lowest index of the lowest value in the range.
Let high = highest index of the highest value in the range.

If v ≤ arr[low], return arr[low].
If v > arr[high], return -1.
Else return index of B.

GT

public static final InequalitySearch GT

Given a sorted array of increasing values arr[] and a key value V, this criterion instructs the binary search algorithm to find the lowest adjacent pair of values {A,B} such that A ≤ V < B.
Let low = lowest index of the lowest value in the range.
Let high = highest index of the highest value in the range.

If v < arr[low], return arr[low].
If v ≥ arr[high], return -1.
Else return index of B.

Method Detail

values

public static InequalitySearch[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (InequalitySearch c : InequalitySearch.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static InequalitySearch valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

find

public static int find(double[] arr,
                       int low,
                       int high,
                       double v,
                       InequalitySearch crit)

Binary Search for the index of the double value in the given search range that satisfies the given InequalitySearch criterion. If -1 is returned there are no values in the search range that satisfy the criterion.

Parameters:

arr - the given array that must be sorted. It must not be null and must not contain any NaN values in the range {low, high} inclusive.

low - the lowest index of the lowest value in the search range, inclusive.

high - the highest index of the highest value in the search range, inclusive.

v - the value to search for. It must not be NaN.

crit - one of LT, LE, EQ, GT, GE. It must not be null.

Returns:

the index of the value in the given search range that satisfies the criterion

find

public static int find(float[] arr,
                       int low,
                       int high,
                       float v,
                       InequalitySearch crit)

Binary Search for the index of the float value in the given search range that satisfies the given InequalitySearch criterion. If -1 is returned there are no values in the search range that satisfy the criterion.

Parameters:

arr - the given array that must be sorted. It must not be null and must not contain any NaN values in the range {low, high} inclusive.

low - the lowest index of the lowest value in the search range, inclusive.

high - the highest index of the highest value in the search range, inclusive.

v - the value to search for. It must not be NaN.

crit - one of LT, LE, EQ, GT, GE

Returns:

the index of the value in the given search range that satisfies the criterion

find

public static int find(long[] arr,
                       int low,
                       int high,
                       long v,
                       InequalitySearch crit)

Binary Search for the index of the long value in the given search range that satisfies the given InequalitySearch criterion. If -1 is returned there are no values in the search range that satisfy the criterion.

Parameters:

arr - the given array that must be sorted.

low - the lowest index of the lowest value in the search range, inclusive.

high - the highest index of the highest value in the search range, inclusive.

v - the value to search for.

crit - one of LT, LE, EQ, GT, GE

Returns:

the index of the value in the given search range that satisfies the criterion