BigDecimal to the power of BigDecimal on Java/Android

Question

I have a simple BigDecimal that I want to power to another BigDecimal, for example 11.11^-1.54. What would be the neatest way to do it in Java/Android? I don't like the idea of converting to doubles because it is for a medical application, so I would appreciate the biggest presicion possible. So far I have reviewed http://commons.apache.org/math/ and math stuff from Google Guava, but found nothing.

Edit: The whole calculation is complex, and has many operations like this. I need as much precision at the end as possible.

Answer 1

A utility class for BigDecimal https://github.com/tareknaj/BigFunctions

Example for z = x^y --> z = exp ( ln(x) * y )

final int SCALE = 10;
BigDecimal x = new BigDecimal(1);
BigDecimal y = new BigDecimal(12);

BigDecimal z = BigFunctions.exp( BigFunctions.ln(x, SCALE).multiply(y),SCALE );

Answer 2

Look into "Java Number Cruncher: The Java Programmer's Guide to Numerical Computing" - Chapter 12.5 Big Decimal Functions : there is some source code with as exact as possible algorithm to compute exponential and logarithm.

Using the mathematical formula : x^y=exp(y*ln(x)) you can achieve a result with maximum precision.

Nevertheless doubles do have a good precision and I strongly recommand you test if it's not precise enough for your need.