81 lines
2.3 KiB
C
81 lines
2.3 KiB
C
/* mpn_dc_div_qr_n -- recursive divide-and-conquer division for arbitrary
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size operands.
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Contributed to the GNU project by Torbjorn Granlund.
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THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. IT IS ONLY
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SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GMP RELEASE.
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Copyright 2006, 2007, 2009 Free Software Foundation, Inc.
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Copyright 2010 William Hart (minor modifications)
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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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#include "longlong.h"
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mp_limb_t
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mpn_dc_div_qr_n (mp_ptr qp, mp_ptr np, mp_srcptr dp, mp_size_t n,
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mp_limb_t dinv, mp_ptr tp)
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{
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mp_size_t lo, hi;
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mp_limb_t cy, qh, ql;
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lo = n >> 1; /* floor(n/2) */
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hi = n - lo; /* ceil(n/2) */
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if (BELOW_THRESHOLD (hi, DC_DIV_QR_THRESHOLD))
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qh = mpn_sb_div_qr (qp + lo, np + 2 * lo, 2 * hi, dp + lo, hi, dinv);
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else
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qh = mpn_dc_div_qr_n (qp + lo, np + 2 * lo, dp + lo, hi, dinv, tp);
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mpn_mul (tp, qp + lo, hi, dp, lo);
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cy = mpn_sub_n (np + lo, np + lo, tp, n);
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if (qh != 0)
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cy += mpn_sub_n (np + n, np + n, dp, lo);
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while (cy != 0)
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{
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qh -= mpn_sub_1 (qp + lo, qp + lo, hi, 1);
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cy -= mpn_add_n (np + lo, np + lo, dp, n);
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}
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if (BELOW_THRESHOLD (lo, DC_DIV_QR_THRESHOLD))
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ql = mpn_sb_div_qr (qp, np + hi, 2 * lo, dp + hi, lo, dinv);
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else
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ql = mpn_dc_div_qr_n (qp, np + hi, dp + hi, lo, dinv, tp);
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mpn_mul (tp, dp, hi, qp, lo);
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cy = mpn_sub_n (np, np, tp, n);
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if (ql != 0)
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cy += mpn_sub_n (np + lo, np + lo, dp, hi);
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while (cy != 0)
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{
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mpn_sub_1 (qp, qp, lo, 1);
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cy -= mpn_add_n (np, np, dp, n);
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}
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return qh;
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}
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