[MATH-1318] Implement reflection formula to digamma function to improve performance on negative values.

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 4.0
• Assignee: Unassigned
• Reporter: Eric Prescott-Gagnon
• Created: 11/Jan/16 13:58
• Updated: 14/May/16 16:24
• Resolved: 14/May/16 16:24

Description

The performance of the digamma( x ) function is in O(|x|) for negative values. Implementing the reflection formula (https://en.wikipedia.org/wiki/Digamma_function#Reflection_formula) can improve the performance in that case.

new pull request: https://github.com/apache/commons-math/pull/32