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author | Kevin Ryde <user42@zip.com.au> | 2001-06-07 22:36:38 +0200 |
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committer | Kevin Ryde <user42@zip.com.au> | 2001-06-07 22:36:38 +0200 |
commit | 9cc56a7c60b0e2392b36c0dcac5a06af7154adbb (patch) | |
tree | 87970d60ebcbfbcbdbd172ff13e4e7ea7d243047 /mpz/lucnum2_ui.c | |
parent | 0d7744a71dad2811fc9e97f4e3a8d402ca017ee8 (diff) | |
download | gmp-9cc56a7c60b0e2392b36c0dcac5a06af7154adbb.tar.gz |
* mpz/fib2_ui.c, mpz/lucnum_ui.c mpz/lucnum2_ui.c: New files.
Diffstat (limited to 'mpz/lucnum2_ui.c')
-rw-r--r-- | mpz/lucnum2_ui.c | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/mpz/lucnum2_ui.c b/mpz/lucnum2_ui.c new file mode 100644 index 000000000..2e92f02df --- /dev/null +++ b/mpz/lucnum2_ui.c @@ -0,0 +1,79 @@ +/* mpz_lucnum2_ui -- calculate Lucas numbers. + +Copyright 2001 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., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, 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 (marker); + + 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 (marker); + 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] */ + c = mpn_lshift (lp, f1p, size, 1); + c += mpn_add_n (lp, lp, l1p, size); + 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 (marker); +} |