71 lines
2.1 KiB
C
71 lines
2.1 KiB
C
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/* Helper function for high degree Toom-Cook algorithms.
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Contributed to the GNU project by Marco Bodrato.
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THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
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SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
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Copyright 2009, 2010 Free Software 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 the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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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 Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
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#include "mpir.h"
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#include "gmp-impl.h"
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/* Gets {pp,n} and (sign?-1:1)*{np,n}. Computes at once:
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{pp,n} <- ({pp,n}+{np,n})/2^{ps+1}
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{pn,n} <- ({pp,n}-{np,n})/2^{ns+1}
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Finally recompose them obtaining:
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{pp,n+off} <- {pp,n}+{np,n}*2^{off*GMP_NUMB_BITS}
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*/
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void
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mpn_toom_couple_handling (mp_ptr pp, mp_size_t n, mp_ptr np,
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int nsign, mp_size_t off, int ps, int ns)
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{
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if (nsign) {
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#ifdef HAVE_NATIVE_mpn_rsh1sub_n
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mpn_rsh1sub_n (np, pp, np, n);
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#else
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mpn_sub_n (np, pp, np, n);
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mpn_rshift (np, np, n, 1);
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#endif
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} else {
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#ifdef HAVE_NATIVE_mpn_rsh1add_n
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mpn_rsh1add_n (np, pp, np, n);
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#else
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mpn_add_n (np, pp, np, n);
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mpn_rshift (np, np, n, 1);
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#endif
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}
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#ifdef HAVE_NATIVE_mpn_rsh1sub_n
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if (ps == 1)
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mpn_rsh1sub_n (pp, pp, np, n);
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else
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#endif
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{
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mpn_sub_n (pp, pp, np, n);
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if (ps > 0)
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mpn_rshift (pp, pp, n, ps);
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}
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if (ns > 0)
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mpn_rshift (np, np, n, ns);
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pp[n] = mpn_add_n (pp+off, pp+off, np, n-off);
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ASSERT_NOCARRY (mpn_add_1(pp+n, np+n-off, off, pp[n]) );
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}
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