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Separate power and factorial calculations to fix large precision loss in exp.

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This commit is contained in:
Arthur Drobot 2017-07-31 22:56:55 -07:00
parent 87f98228d0
commit f68f184945
1 changed files with 7 additions and 5 deletions
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12
src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java
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@ -171,17 +171,19 @@ public class StandardPlugin extends Plugin {
//We need n such that x^(n+1) * 3^ceil(x) <= maxError * (n+1)!.
//right and left refer to lhs and rhs in the above inequality.
NumberInterface sum = NaiveNumber.ONE.promoteTo(params[0].getClass());
NumberInterface nextTerm = params[0];
NumberInterface left = params[0].multiply(new NaiveNumber(3).promoteTo(params[0].getClass()).intPow(params[0].ceiling())), right = maxError;
NumberInterface nextNumerator = params[0];
NumberInterface left = params[0].multiply((new NaiveNumber(3)).promoteTo(params[0].getClass()).intPow(params[0].ceiling())), right = maxError;
do{
sum = sum.add(nextTerm);
sum = sum.add(nextNumerator.divide(factorial(params[0].getClass(), n+1)));
n++;
NumberInterface nextN = new NaiveNumber(n+1).promoteTo(params[0].getClass());
nextTerm = nextTerm.multiply(params[0]).divide(nextN);
nextNumerator = nextNumerator.multiply(params[0]);
left = left.multiply(params[0]);
NumberInterface nextN = (new NaiveNumber(n+1)).promoteTo(params[0].getClass());
right = right.multiply(nextN);
//System.out.println(left + ", " + right);
}
while(left.compareTo(right) > 0);
System.out.println(n+1);
return sum;
}
}