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Optimize log.

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This commit is contained in:
Arthur Drobot 2017-07-31 12:39:56 -07:00
parent 5bb7c1dc6b
commit 0172b178de
1 changed files with 4 additions and 3 deletions
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7
src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java
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@ -203,11 +203,12 @@ public class StandardPlugin extends Plugin {
private NumberInterface getLogPartialSum(NumberInterface x) {
NumberInterface maxError = getMaxError(x);
x = x.subtract(NaiveNumber.ONE.promoteTo(x.getClass())); //Terms used are for log(x+1).
NumberInterface currentTerm = x, sum = x;
NumberInterface currentNumerator = x, currentTerm = x, sum = x;
int n = 1;
while (FUNCTION_ABS.apply(currentTerm).compareTo(maxError) > 0) {
n++;
currentTerm = currentTerm.multiply(x).multiply((new NaiveNumber(n - 1)).promoteTo(x.getClass())).divide((new NaiveNumber(n)).promoteTo(x.getClass())).negate();
currentNumerator = currentNumerator.multiply(x).negate();
currentTerm = currentNumerator.divide(new NaiveNumber(n).promoteTo(x.getClass()));
sum = sum.add(currentTerm);
}
return sum;
@ -273,7 +274,7 @@ public class StandardPlugin extends Plugin {
*
* @param maxError Maximum error permissible (This should probably be positive.)
* @param x where the function is evaluated.
* @return the number of terms needed to evaluated the exponential function.
* @return the number of terms needed to evaluate the exponential function.
*/
private static int getNTermsExp(NumberInterface maxError, NumberInterface x) {
//We need n such that |x^(n+1)| <= (n+1)! * maxError