randoop.util

Class Randomness

java.lang.Object

randoop.util.Randomness

public final class Randomness
extends java.lang.Object

A simple-to-use wrapper around Random.

It also supports logging, for debugging of apparently nondeterministic behavior.

Field Summary

Fields

Modifier and Type	Field and Description
static long	DEFAULT_SEED The default initial seed for the random number generator.
private static java.util.Random	random The random generator that makes random choices.
private static int	totalCallsToRandom Number of calls to the underlying Random instance that this wraps.
static int	verbosity 0 = no output, 1 = brief output, 2 = verbose output.

Constructor Summary

Constructors

Modifier	Constructor and Description
private	Randomness()

Method Summary

Modifier and Type	Method and Description
private static void	incrementCallsToRandom(java.lang.String caller) Call this before every use of Randomness.random.
private static void	logSelection(java.lang.Object returnValue, java.lang.String methodName, java.lang.Object argument) Logs the value that was randomly selected, along with the calling method and its argument.
static double	nextRandomGaussian(double mean, double stdDev) Returns a gaussianly-distributed random number.
static int	nextRandomInt(int i) Uniformly random int from [0, i) = from [0, i-1].
static <T> T	nthMember(java.lang.Iterable<T> ible, int n) Returns the nth element (0-indexed) from the iterable.
static boolean	randomBoolFromDistribution(double falseProb, double trueProb) Return true or false with the given relative probabilites, which need not add to 1.
static <T> T	randomMember(java.util.Collection<T> c) Returns a randomly-chosen member of the collection.
static <T> T	randomMember(SimpleList<T> list) Returns a randomly-chosen member of the list.
static <T> T	randomMemberWeighted(SimpleList<T> list, java.util.Map<T,java.lang.Double> weights) Randomly selects an element from a weighted distribution of elements.
static <T> T	randomMemberWeighted(SimpleList<T> list, java.util.Map<T,java.lang.Double> weights, double totalWeight) Randomly selects an element from a weighted distribution of elements.
static <T> T	randomSetMember(java.util.Collection<T> set) Return a random member of the set, selected uniformly at random.
static void	setSeed(long seed) Sets the seed of this random number generator.
private static java.lang.String	toString(java.lang.Object o) Produces a printed representation of the object, depending on the verbosity level.
static boolean	weightedCoinFlip(double trueProb) Return true with probability trueProb, otherwise false.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

verbosity

public static int verbosity

0 = no output, 1 = brief output, 2 = verbose output.

DEFAULT_SEED

public static final long DEFAULT_SEED

The default initial seed for the random number generator.

See Also:

Constant Field Values

random

private static java.util.Random random

The random generator that makes random choices. (Developer note: do not declare new Random objects; use this one instead).

totalCallsToRandom

private static int totalCallsToRandom

Number of calls to the underlying Random instance that this wraps.

Constructor Detail

Randomness

private Randomness()

Method Detail

setSeed

public static void setSeed(long seed)

Sets the seed of this random number generator.

Parameters:

seed - the initial seed

incrementCallsToRandom

private static void incrementCallsToRandom(java.lang.String caller)

Call this before every use of Randomness.random.

Parameters:

caller - the name of the method that called Randomness.random

nextRandomInt

public static int nextRandomInt(int i)

Uniformly random int from [0, i) = from [0, i-1].

Parameters:

i - upper bound on range for generated values

Returns:

a value selected from range [0, i)

nextRandomGaussian

public static double nextRandomGaussian(double mean,
                                        double stdDev)

Returns a gaussianly-distributed random number.

Parameters:

mean - the mean of the distribution

stdDev - the standard deviation of the distribution

Returns:

a value selected from the distribution

randomMember

public static <T> T randomMember(SimpleList<T> list)

Returns a randomly-chosen member of the list.

Type Parameters:

T - the type of list elements

Parameters:

list - the list from which to choose a random member

Returns:

a randomly-chosen member of the list

randomMember

public static <T> T randomMember(java.util.Collection<T> c)

Returns a randomly-chosen member of the collection.

Type Parameters:

T - the type of collection elements

Parameters:

c - the collection from which to choose a random member

Returns:

a randomly-chosen member of the collection

nthMember

public static <T> T nthMember(java.lang.Iterable<T> ible,
                              int n)

Returns the nth element (0-indexed) from the iterable.

Type Parameters:

T - the type of elements in the iterable

Parameters:

ible - an iterable that has at least n+1 elements

n - the 0-based index of the member to return

Returns:

the the nth element (0-indexed) from the iterable

randomMemberWeighted

public static <T> T randomMemberWeighted(SimpleList<T> list,
                                         java.util.Map<T,java.lang.Double> weights)

Randomly selects an element from a weighted distribution of elements. These weights are with respect to each other. They are not normalized (they might add up to any value).

Type Parameters:

T - the type of the elements in the list

Parameters:

list - the list of elements to select from

weights - the map of elements to their weights. Each element's weight must be non-negative. An element with a weight of zero will never be selected.

Returns:

a randomly selected element from list

randomMemberWeighted

public static <T> T randomMemberWeighted(SimpleList<T> list,
                                         java.util.Map<T,java.lang.Double> weights,
                                         double totalWeight)

Randomly selects an element from a weighted distribution of elements. These weights are with respect to each other. They are not normalized (they might add up to any value).

Type Parameters:

T - the type of the elements in the list

Parameters:

list - the list of elements to select from

weights - the map of elements to their weights. Each element's weight must be non-negative. An element with a weight of zero will never be selected.

totalWeight - the total weight of the elements of the list

Returns:

a randomly selected element from list

randomSetMember

public static <T> T randomSetMember(java.util.Collection<T> set)

Return a random member of the set, selected uniformly at random.

Type Parameters:

T - the type of elements of the set param set the collection from which to choose an element

Parameters:

set - the collection from which to select an element

Returns:

a randomly-selected member of the set

weightedCoinFlip

public static boolean weightedCoinFlip(double trueProb)

Return true with probability trueProb, otherwise false.

Parameters:

trueProb - the likelihood that true is returned; must be within [0..1]

Returns:

true with likelihood trueProb; otherwise false

randomBoolFromDistribution

public static boolean randomBoolFromDistribution(double falseProb,
                                                 double trueProb)

Return true or false with the given relative probabilites, which need not add to 1.

Parameters:

falseProb - the likelihood that true is returned; an arbitrary non-negative number

trueProb - the likelihood that true is returned; an arbitrary non-negative number

Returns:

true or false, with the given probabilities

logSelection

private static void logSelection(java.lang.Object returnValue,
                                 java.lang.String methodName,
                                 java.lang.Object argument)

Logs the value that was randomly selected, along with the calling method and its argument.

Parameters:

returnValue - the value randomly selected

methodName - the name of the method called

argument - the method argument

toString

private static java.lang.String toString(java.lang.Object o)

Produces a printed representation of the object, depending on the verbosity level.

Parameters:

o - the object to produce a printed representation of

Returns:

a printed representation of the argument

See Also:

verbosity