water.util

Class MathUtils

java.lang.Object

water.util.MathUtils

public class MathUtils
extends java.lang.Object

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MathUtils.Norm

Field Summary

Fields

Modifier and Type	Field and Description
static long[]	PRIMES

Constructor Summary

Constructors

Constructor and Description
MathUtils()

Method Summary

Methods

Modifier and Type	Method and Description
static double	approxExp(double x) Fast approximate exp
static double	approxInvSqrt(double x) Fast approximate 1./sqrt
static float	approxInvSqrt(float x) Fast approximate 1./sqrt
static double	approxLog(double x) Fast approximate log for values greater than 1, otherwise exact
static double	approxSqrt(double x) Fast approximate sqrt
static float	approxSqrt(float x) Fast approximate sqrt
static float	approxSumSquares(float[] a, int from, int to) Approximate sumSquares
static boolean	compare(double a, double b, double abseps, double releps) Compare 2 doubles within a tolerance
static double[]	div(double[] nums, double n)
static float[]	div(float[] nums, float n)
static boolean	equalsWithinOneSmallUlp(double a, double b)
static boolean	equalsWithinOneSmallUlp(float a, float b) Compare two numbers to see if they are within one ulp of the smaller decade.
static double	innerProduct(double[] x, double[] y)
static double	l1norm(double[] x)
static double	l2norm(double[] x)
static double	l2norm2(double[] x)
static int	log2(int n) Fast calculation of log base 2 for integers.
static double[]	min_max_mean_stddev(long[] counts)
static double	roundToNDigits(double d, int n)
static double	sum(double[] from)
static float	sum(float[] from)
static float	sumSquares(float[] a)
static float	sumSquares(float[] a, int from, int to)
static double[]	wadd(double[] x, double[] y, double w)

Methods inherited from class java.lang.Object

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

Field Detail

PRIMES

public static final long[] PRIMES

Constructor Detail

MathUtils

public MathUtils()

Method Detail

approxSqrt

public static double approxSqrt(double x)

Fast approximate sqrt

Returns:

sqrt(x) with up to 5% relative error

approxSqrt

public static float approxSqrt(float x)

Fast approximate sqrt

Returns:

sqrt(x) with up to 5% relative error

approxInvSqrt

public static double approxInvSqrt(double x)

Fast approximate 1./sqrt

Returns:

1./sqrt(x) with up to 2% relative error

approxInvSqrt

public static float approxInvSqrt(float x)

Fast approximate 1./sqrt

Returns:

1./sqrt(x) with up to 2% relative error

approxExp

public static double approxExp(double x)

Fast approximate exp

Returns:

exp(x) with up to 5% relative error

approxLog

public static double approxLog(double x)

Fast approximate log for values greater than 1, otherwise exact

Returns:

log(x) with up to 0.1% relative error

log2

public static int log2(int n)

Fast calculation of log base 2 for integers.

Returns:

log base 2 of n

div

public static float[] div(float[] nums,
          float n)

div

public static double[] div(double[] nums,
           double n)

sum

public static float sum(float[] from)

sum

public static double sum(double[] from)

sumSquares

public static float sumSquares(float[] a)

approxSumSquares

public static float approxSumSquares(float[] a,
                     int from,
                     int to)

Approximate sumSquares

Parameters:

a - Array with numbers

from - starting index (inclusive)

to - ending index (exclusive)

Returns:

approximate sum of squares based on a sample somewhere in the middle of the array (pos determined by bits of a[0])

sumSquares

public static float sumSquares(float[] a,
               int from,
               int to)

equalsWithinOneSmallUlp

public static boolean equalsWithinOneSmallUlp(float a,
                              float b)

Compare two numbers to see if they are within one ulp of the smaller decade. Order of the arguments does not matter.

Parameters:

a - First number

b - Second number

Returns:

true if a and b are essentially equal, false otherwise.

equalsWithinOneSmallUlp

public static boolean equalsWithinOneSmallUlp(double a,
                              double b)

compare

public static boolean compare(double a,
              double b,
              double abseps,
              double releps)

Compare 2 doubles within a tolerance

Parameters:

a - double

b - double

abseps - - Absolute allowed tolerance

releps - - Relative allowed tolerance

Returns:

true if equal within tolerances

innerProduct

public static double innerProduct(double[] x,
                  double[] y)

l2norm2

public static double l2norm2(double[] x)

l1norm

public static double l1norm(double[] x)

l2norm

public static double l2norm(double[] x)

wadd

public static double[] wadd(double[] x,
            double[] y,
            double w)

roundToNDigits

public static double roundToNDigits(double d,
                    int n)

min_max_mean_stddev

public static double[] min_max_mean_stddev(long[] counts)