## File: auxarith.c

package info (click to toggle)
gmp-ecm 7.0.4+ds-5
 `123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109` ``````/* Auxiliary arithmetic routines on unsigned long ints for the ecm library. Copyright 2001, 2002, 2003, 2004, 2005, 2007, 2008 Paul Zimmermann and Alexander Kruppa. This file is part of the ECM Library. The ECM Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. The ECM Library 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the ECM Library; see the file COPYING.LIB. If not, see http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ #include "config.h" #include "ecm-impl.h" /* Returns the gcd of a and b */ unsigned long gcd (unsigned long a, unsigned long b) { unsigned long t; while (b != 0UL) { t = a % b; a = b; b = t; } return a; } /* returns Euler's totient phi function */ unsigned long eulerphi (unsigned long n) { unsigned long phi = 1UL, p; for (p = 2UL; p * p <= n; p += 2UL) { if (n % p == 0UL) { phi *= p - 1UL; n /= p; while (n % p == 0UL) { phi *= p; n /= p; } } if (p == 2UL) p--; } /* now n is prime or 1 */ return (n == 1UL) ? phi : phi * (n - 1UL); } /* returns ceil(log(n)/log(2)) */ unsigned int ceil_log2 (unsigned long n) { unsigned int k = 0; ASSERT (n > 0UL); n--; while (n) { k++; n >>= 1; } return k; } /* Returns the smallest prime factor of N. If N == 1, return 1. */ unsigned long find_factor (const unsigned long N) { unsigned long i; ASSERT_ALWAYS (N != 0UL); if (N == 1UL) return 1UL; if (N % 2UL == 0UL) return 2UL; for (i = 3UL; i*i <= N; i += 2UL) if (N % i == 0UL) return i; return N; } ``````