toom_couple_handling.c
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上传日期:2022-08-06
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- /* Helper function for high degree Toom-Cook algorithms.
- Contributed to the GNU project by Marco Bodrato.
- THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
- SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
- GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
- Copyright 2009, 2010 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 3 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. If not, see http://www.gnu.org/licenses/. */
- #include "gmp.h"
- #include "gmp-impl.h"
- /* Gets {pp,n} and (sign?-1:1)*{np,n}. Computes at once:
- {pp,n} <- ({pp,n}+{np,n})/2^{ps+1}
- {pn,n} <- ({pp,n}-{np,n})/2^{ns+1}
- Finally recompose them obtaining:
- {pp,n+off} <- {pp,n}+{np,n}*2^{off*GMP_NUMB_BITS}
- */
- void
- mpn_toom_couple_handling (mp_ptr pp, mp_size_t n, mp_ptr np,
- int nsign, mp_size_t off, int ps, int ns)
- {
- if (nsign) {
- #ifdef HAVE_NATIVE_mpn_rsh1sub_n
- mpn_rsh1sub_n (np, pp, np, n);
- #else
- mpn_sub_n (np, pp, np, n);
- mpn_rshift (np, np, n, 1);
- #endif
- } else {
- #ifdef HAVE_NATIVE_mpn_rsh1add_n
- mpn_rsh1add_n (np, pp, np, n);
- #else
- mpn_add_n (np, pp, np, n);
- mpn_rshift (np, np, n, 1);
- #endif
- }
- #ifdef HAVE_NATIVE_mpn_rsh1sub_n
- if (ps == 1)
- mpn_rsh1sub_n (pp, pp, np, n);
- else
- #endif
- {
- mpn_sub_n (pp, pp, np, n);
- if (ps > 0)
- mpn_rshift (pp, pp, n, ps);
- }
- if (ns > 0)
- mpn_rshift (np, np, n, ns);
- pp[n] = mpn_add_n (pp+off, pp+off, np, n-off);
- ASSERT_NOCARRY (mpn_add_1(pp+n, np+n-off, off, pp[n]) );
- }