Annotation of OpenXM_contrib/gmp/mpz/lucnum2_ui.c, Revision 1.1.1.1
1.1 ohara 1: /* mpz_lucnum2_ui -- calculate Lucas numbers.
2:
3: Copyright 2001 Free Software Foundation, Inc.
4:
5: This file is part of the GNU MP Library.
6:
7: The GNU MP Library is free software; you can redistribute it and/or modify
8: it under the terms of the GNU Lesser General Public License as published by
9: the Free Software Foundation; either version 2.1 of the License, or (at your
10: option) any later version.
11:
12: The GNU MP Library is distributed in the hope that it will be useful, but
13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
15: License for more details.
16:
17: You should have received a copy of the GNU Lesser General Public License
18: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20: MA 02111-1307, USA. */
21:
22: #include <stdio.h>
23: #include "gmp.h"
24: #include "gmp-impl.h"
25:
26:
27: void
28: mpz_lucnum2_ui (mpz_ptr ln, mpz_ptr lnsub1, unsigned long n)
29: {
30: mp_ptr lp, l1p, f1p;
31: mp_size_t size;
32: mp_limb_t c;
33: TMP_DECL (marker);
34:
35: ASSERT (ln != lnsub1);
36:
37: /* handle small n quickly, and hide the special case for L[-1]=-1 */
38: if (n <= FIB_TABLE_LUCNUM_LIMIT)
39: {
40: mp_limb_t f = FIB_TABLE (n);
41: mp_limb_t f1 = FIB_TABLE ((int) n - 1);
42:
43: /* L[n] = F[n] + 2F[n-1] */
44: PTR(ln)[0] = f + 2*f1;
45: SIZ(ln) = 1;
46:
47: /* L[n-1] = 2F[n] - F[n-1], but allow for L[-1]=-1 */
48: PTR(lnsub1)[0] = (n == 0 ? 1 : 2*f - f1);
49: SIZ(lnsub1) = (n == 0 ? -1 : 1);
50:
51: return;
52: }
53:
54: TMP_MARK (marker);
55: size = MPN_FIB2_SIZE (n);
56: f1p = TMP_ALLOC_LIMBS (size);
57:
58: MPZ_REALLOC (ln, size+1);
59: MPZ_REALLOC (lnsub1, size+1);
60: lp = PTR(ln);
61: l1p = PTR(lnsub1);
62:
63: size = mpn_fib2_ui (l1p, f1p, n);
64:
65: /* L[n] = F[n] + 2F[n-1] */
66: c = mpn_lshift (lp, f1p, size, 1);
67: c += mpn_add_n (lp, lp, l1p, size);
68: lp[size] = c;
69: SIZ(ln) = size + (c != 0);
70:
71: /* L[n-1] = 2F[n] - F[n-1] */
72: c = mpn_lshift (l1p, l1p, size, 1);
73: c -= mpn_sub_n (l1p, l1p, f1p, size);
74: ASSERT ((mp_limb_signed_t) c >= 0);
75: l1p[size] = c;
76: SIZ(lnsub1) = size + (c != 0);
77:
78: TMP_FREE (marker);
79: }
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>