Annotation of OpenXM_contrib/gmp/mpz/lucnum2_ui.c, Revision 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: }
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