How to implement logarithm with GMP

Marc Glisse marc.glisse at
Tue May 14 11:09:07 CEST 2013

On Mon, 13 May 2013, Shouwei Li wrote:

> Hi there,
> I am using GMP to implement the "Agrawal Kayal and Saxena algorithm" which
> is a deterministic algorithm for primality, but the GMP library does not
> support logarithm operation.
> I want to know is there any other method that I could implement a private
> version of log function.
> Thank you very much!

Depending on what your exact need is, either the logarithm is the position 
of the highest 1 in the number (see mpz_sizeinbase), or you want mpfr.

Marc Glisse

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