[jira] [Resolved] (NUMBERS-172) Update the Erf function to use the Boost rational function approximtion

["Alex Herbert (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/NUMBERS-172?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alex Herbert resolved NUMBERS-172.
----------------------------------
    Fix Version/s: 1.1
       Resolution: Implemented

Added in commit:

a0e56e1fd241d9fd77973c137c0608dc12ff44f0

> Update the Erf function to use the Boost rational function approximtion
> -----------------------------------------------------------------------
>
>                 Key: NUMBERS-172
>                 URL: https://issues.apache.org/jira/browse/NUMBERS-172
>             Project: Commons Numbers
>          Issue Type: Improvement
>          Components: gamma
>    Affects Versions: 1.0
>            Reporter: Alex Herbert
>            Priority: Major
>             Fix For: 1.1
>
>          Time Spent: 1h
>  Remaining Estimate: 0h
>
> The error function (erf) and complementary error function (erfc) are implemented using the continued fraction evaluation performed in the regularized gamma P and Q implementation. This is a generic function called with a fixed argument of 0.5:
> {noformat}
> erf(x)  = gammap(0.5, x*x)
> erfc(x) = gammaq(0.5, x*x)
> {noformat}
> These functions have an implementation in the Boost c++ library using a rational function approximation.
> NUMBERS-171 ported the inverse erf functions from Boost with an improvement in accuracy and speed. Investigate the use of the corresponding forward erf and erfc functions from Boost as replacements for the use of the regularized gamma function to evaluate the error function.



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