pqc/external/flint-2.4.3/ulong_extras/prime_pi_bounds.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License,or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not,write to the Free Software
Foundation,Inc.,51 Franklin St,Fifth Floor,Boston,MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2009 William Hart
Copyright (C) 2010 Fredrik Johansson
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
void n_prime_pi_bounds(ulong *lo, ulong *hi, mp_limb_t n)
{
int lg2 = FLINT_BIT_COUNT(n);
*lo = (ulong)(((double)n)/((double)lg2*0.6931472));
*hi = (ulong)(((double)n)/((double)(lg2-1)*0.5522821));
}