gcc/gmp/mpz/lcm.c

/* mpz_lcm -- mpz/mpz least common multiple.

Copyright 1996, 2000, 2001, 2005 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP 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 GNU MP 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 GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */

#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"


void
mpz_lcm (mpz_ptr r, mpz_srcptr u, mpz_srcptr v)
{
  mpz_t g;
  mp_size_t usize, vsize, size;
  TMP_DECL;

  usize = SIZ (u);
  vsize = SIZ (v);
  if (usize == 0 || vsize == 0)
    {
      SIZ (r) = 0;
      return;
    }
  usize = ABS (usize);
  vsize = ABS (vsize);

  if (vsize == 1)
    {
      mp_limb_t  vl, gl, c;
      mp_srcptr  up;
      mp_ptr     rp;

    one:
      MPZ_REALLOC (r, usize+1);

      up = PTR(u);
      vl = PTR(v)[0];
      gl = mpn_gcd_1 (up, usize, vl);
      vl /= gl;

      rp = PTR(r);
      c = mpn_mul_1 (rp, up, usize, vl);
      rp[usize] = c;
      usize += (c != 0);
      SIZ(r) = usize;
      return;
    }

  if (usize == 1)
    {
      usize = vsize;
      MPZ_SRCPTR_SWAP (u, v);
      goto one;
    }

  TMP_MARK;
  size = MAX (usize, vsize);
  MPZ_TMP_INIT (g, size);

  mpz_gcd (g, u, v);
  mpz_divexact (g, u, g);
  mpz_mul (r, g, v);

  SIZ (r) = ABS (SIZ (r));	/* result always positive */

  TMP_FREE;
}