com.numericalmethod.suanshu.misc

Class SuanShuUtils

java.lang.Object

com.numericalmethod.suanshu.misc.SuanShuUtils

public class SuanShuUtils
extends java.lang.Object

These are some miscellaneous utility functions that are commonly used throughout the SuanShu library.

Method Summary

Modifier and Type	Method and Description
static void	assertArgument(boolean condition, java.lang.String errorMessage, java.lang.Object... args) Check if an argument condition is satisfied.
static void	assertOrThrow(java.lang.RuntimeException error) This is a wrapper method that throws a RuntimeException if it is not null.
static double	autoEpsilon(double... inputs) Guess a reasonable precision parameter.
static double	autoEpsilon(double[]... inputs) Guess a reasonable precision parameter.
static double	autoEpsilon(MatrixTable A) Guess a reasonable precision parameter.

Methods inherited from class java.lang.Object

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

Method Detail

assertArgument

public static void assertArgument(boolean condition,
                                  java.lang.String errorMessage,
                                  java.lang.Object... args)

Check if an argument condition is satisfied. Throw IllegalArgumentException if not.

Parameters:

condition - the argument condition to be checked

errorMessage - the error message if the condition is not satisfied (format string can be used with args, see format)

args - the arguments for the error message

assertOrThrow

public static void assertOrThrow(java.lang.RuntimeException error)

This is a wrapper method that throws a RuntimeException if it is not null. To use this method efficiently, we need to avoid the slow and expensive creation of an exception object on each checking. For a sample usage,

assertOrThrow(cond ? null : new RuntimeException("msg"));

It is important that we use lazy evaluation of the if statement.

Parameters:

error - the error thrown if the condition is not satisfied

autoEpsilon

public static double autoEpsilon(double... inputs)

Guess a reasonable precision parameter. In numerical computing, we often need to guess how small a number needs to be for it to be considered 0. Changing the threshold often changes the results, e.g., the numerical rank of a matrix.

This method suggests a more 'objective' way to determine the 'correct' epsilon from the inputs. Roughly,

auto ε = |max(inputs)| * sqrt(number of inputs) * machine ε * 10

Parameters:

inputs - doubles

Returns:

a precision parameter

autoEpsilon

public static double autoEpsilon(double[]... inputs)

Guess a reasonable precision parameter. In numerical computing, we often need to guess how small a number needs to be for it to be considered 0. Changing the threshold often changes the results, e.g., the numerical rank of a matrix.

This method suggests a more 'objective' way to determine the 'correct' epsilon from the inputs. Roughly,

auto ε = |max(inputs)| * sqrt(number of inputs) * machine ε * 10

Parameters:

inputs - arrays of double[]s

Returns:

a precision parameter

autoEpsilon

public static double autoEpsilon(MatrixTable A)

Guess a reasonable precision parameter. In numerical computing, we often need to guess how small a number needs to be for it to be considered 0. Changing the threshold often changes the results, e.g., the numerical rank of a matrix.

This method suggests a more 'objective' way to determine the 'correct' epsilon from the inputs. Roughly,

auto ε = |max(inputs)| * sqrt(number of inputs) * machine ε * 10

Parameters:

A - a matrix

Returns:

a precision parameter