84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
|
/* mpz_lucnum2_ui -- calculate Lucas numbers.
|
||
|
|
|
||
|
|
Copyright 2001, 2003, 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 2.1 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; see the file COPYING.LIB. If not, write to
|
||
|
|
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
|
||
|
|
MA 02110-1301, USA. */
|
||
|
|
|
||
|
|
#include <stdio.h>
|
||
|
|
#include "gmp.h"
|
||
|
|
#include "gmp-impl.h"
|
||
|
|
|
||
|
|
|
||
|
|
void
|
||
|
|
mpz_lucnum2_ui (mpz_ptr ln, mpz_ptr lnsub1, unsigned long n)
|
||
|
|
{
|
||
|
|
mp_ptr lp, l1p, f1p;
|
||
|
|
mp_size_t size;
|
||
|
|
mp_limb_t c;
|
||
|
|
TMP_DECL;
|
||
|
|
|
||
|
|
ASSERT (ln != lnsub1);
|
||
|
|
|
||
|
|
/* handle small n quickly, and hide the special case for L[-1]=-1 */
|
||
|
|
if (n <= FIB_TABLE_LUCNUM_LIMIT)
|
||
|
|
{
|
||
|
|
mp_limb_t f = FIB_TABLE (n);
|
||
|
|
mp_limb_t f1 = FIB_TABLE ((int) n - 1);
|
||
|
|
|
||
|
|
/* L[n] = F[n] + 2F[n-1] */
|
||
|
|
PTR(ln)[0] = f + 2*f1;
|
||
|
|
SIZ(ln) = 1;
|
||
|
|
|
||
|
|
/* L[n-1] = 2F[n] - F[n-1], but allow for L[-1]=-1 */
|
||
|
|
PTR(lnsub1)[0] = (n == 0 ? 1 : 2*f - f1);
|
||
|
|
SIZ(lnsub1) = (n == 0 ? -1 : 1);
|
||
|
|
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
TMP_MARK;
|
||
|
|
size = MPN_FIB2_SIZE (n);
|
||
|
|
f1p = TMP_ALLOC_LIMBS (size);
|
||
|
|
|
||
|
|
MPZ_REALLOC (ln, size+1);
|
||
|
|
MPZ_REALLOC (lnsub1, size+1);
|
||
|
|
lp = PTR(ln);
|
||
|
|
l1p = PTR(lnsub1);
|
||
|
|
|
||
|
|
size = mpn_fib2_ui (l1p, f1p, n);
|
||
|
|
|
||
|
|
/* L[n] = F[n] + 2F[n-1] */
|
||
|
|
#if HAVE_NATIVE_mpn_addlsh1_n
|
||
|
|
c = mpn_addlsh1_n (lp, l1p, f1p, size);
|
||
|
|
#else
|
||
|
|
c = mpn_lshift (lp, f1p, size, 1);
|
||
|
|
c += mpn_add_n (lp, lp, l1p, size);
|
||
|
|
#endif
|
||
|
|
lp[size] = c;
|
||
|
|
SIZ(ln) = size + (c != 0);
|
||
|
|
|
||
|
|
/* L[n-1] = 2F[n] - F[n-1] */
|
||
|
|
c = mpn_lshift (l1p, l1p, size, 1);
|
||
|
|
c -= mpn_sub_n (l1p, l1p, f1p, size);
|
||
|
|
ASSERT ((mp_limb_signed_t) c >= 0);
|
||
|
|
l1p[size] = c;
|
||
|
|
SIZ(lnsub1) = size + (c != 0);
|
||
|
|
|
||
|
|
TMP_FREE;
|
||
|
|
}
|