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4c74403188
Change-Id: Iae65e95cfa0d92091b8b0a424ae36d88efa76aa9 Reviewed-on: https://review.haiku-os.org/c/buildtools/+/3020 Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
95 lines
2.4 KiB
C
95 lines
2.4 KiB
C
/* mpz_lucnum2_ui -- calculate Lucas numbers.
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Copyright 2001, 2003, 2005, 2012, 2015, 2016, 2018 Free Software
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Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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or both in parallel, as here.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library. If not,
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see https://www.gnu.org/licenses/. */
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#include <stdio.h>
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#include "gmp-impl.h"
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void
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mpz_lucnum2_ui (mpz_ptr ln, mpz_ptr lnsub1, unsigned long n)
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{
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mp_ptr lp, l1p, f1p;
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mp_size_t size;
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mp_limb_t c;
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TMP_DECL;
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ASSERT (ln != lnsub1);
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/* handle small n quickly, and hide the special case for L[-1]=-1 */
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if (n <= FIB_TABLE_LUCNUM_LIMIT)
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{
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mp_limb_t f = FIB_TABLE (n);
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mp_limb_t f1 = FIB_TABLE ((int) n - 1);
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/* L[n] = F[n] + 2F[n-1] */
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MPZ_NEWALLOC (ln, 1)[0] = f + 2*f1;
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SIZ(ln) = 1;
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/* L[n-1] = 2F[n] - F[n-1], but allow for L[-1]=-1 */
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MPZ_NEWALLOC (lnsub1, 1)[0] = (n == 0 ? 1 : 2*f - f1);
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SIZ(lnsub1) = (n == 0 ? -1 : 1);
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return;
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}
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TMP_MARK;
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size = MPN_FIB2_SIZE (n);
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f1p = TMP_ALLOC_LIMBS (size);
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lp = MPZ_NEWALLOC (ln, size+1);
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l1p = MPZ_NEWALLOC (lnsub1, size+1);
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size = mpn_fib2_ui (l1p, f1p, n);
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/* L[n] = F[n] + 2F[n-1] */
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#if HAVE_NATIVE_mpn_addlsh1_n
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c = mpn_addlsh1_n (lp, l1p, f1p, size);
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#else
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c = mpn_lshift (lp, f1p, size, 1);
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c += mpn_add_n (lp, lp, l1p, size);
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#endif
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lp[size] = c;
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SIZ(ln) = size + (c != 0);
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/* L[n-1] = 2F[n] - F[n-1] */
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#if HAVE_NATIVE_mpn_rsblsh1_n
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c = mpn_rsblsh1_n (l1p, f1p, l1p, size);
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#else
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c = mpn_lshift (l1p, l1p, size, 1);
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c -= mpn_sub_n (l1p, l1p, f1p, size);
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#endif
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ASSERT ((mp_limb_signed_t) c >= 0);
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l1p[size] = c;
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SIZ(lnsub1) = size + (c != 0);
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TMP_FREE;
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}
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