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 03072011, 09:05 AM #1Member
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 03072011, 12:37 PM #2
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Is n very big? i.e. n > Double.MAX_VALUE. If so you have to approximate those logs. The disadvantage with approximating a log with, say, a Taylor or McLaurin series is that they become quite inaccurate for large values. A way to reduce the inaccuracy is:
log(x+y) == log(y)+log(1+y/x))
for suitable values of x and y when x+y == n. If you can elaborate on this, feel free to reply here.
kind regards,
JosBuild a wall around Donald Trump; I'll pay for it.
 03082011, 04:56 AM #3Member
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Thank you josAH for quick reply...
n is very big,i.e n>>Double.maxvalue,
actually iam implementing quadratic sieve algorithm for integer factorization problem..
in that i have to find lognloglogn value..
 03082011, 06:15 AM #4Senior Member
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If numerical accuracy is desired (I'm assuming it is), I'd write a log function using the BigInteger and BigDecimal classes directly.
You might consider talking to a mathematician. This function appears to me to be monotonic, and so a gradient descent (NewtonRaphson) approach may work and provide a solution much faster than direct computation.
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