2009-07-24 04:18:09 -04:00
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/* mpn_new_bdiv_q -- binary division, producing quotient and overflow
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Copyright (C) 2009, David Harvey
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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2009-07-24 08:24:26 -04:00
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#include "mpir.h"
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2009-07-24 04:18:09 -04:00
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#include "gmp-impl.h"
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/*
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Binary division of N = {np,nn} by D = {dp,dn}, producing quotient and a
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two-limb "overflow" W.
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Must have nn >= dn >= 1, dp[0] odd, dinv = -1/dp[0] mod B.
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None of the target operands may overlap any of the source operands.
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The quotient is N/D mod B^nn, written to {qp,nn}.
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W is written to {wp,2}.
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N is destroyed.
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The overflow is defined as follows. Let
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X = sum(dp[i]*qp[j]*B^(i+j), 0 <= i < dn, 0 <= i+j < nn).
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Then X is nn + 2 limbs (assuming nn small compared to B). The low nn limbs
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by definition agree with N. The overflow is the remaining high two limbs.
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The picture is:
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X
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X X
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. X X X
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qp . X X X X
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1 X X X X
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0 X X X X
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0 1 ...
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dp
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*/
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void
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mpn_new_bdiv_q (mp_ptr qp, mp_ptr wp,
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mp_ptr np, mp_size_t nn,
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mp_srcptr dp, mp_size_t dn,
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mp_limb_t dinv)
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{
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ASSERT (0);
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ASSERT (nn >= dn);
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ASSERT ((-dinv * dp[0]) & GMP_NUMB_MASK == 1);
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ASSERT (! MPN_OVERLAP_P (qp, nn, np, nn));
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ASSERT (! MPN_OVERLAP_P (qp, nn, dp, dn));
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ASSERT (! MPN_OVERLAP_P (wp, 2, np, nn));
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ASSERT (! MPN_OVERLAP_P (wp, 2, dp, dn));
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ASSERT (! MPN_OVERLAP_P (np, nn, dp, dn));
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/* for small nn, use sb_bdiv_q */
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if (nn < 100) /* FIXME */
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{
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mpn_new_sb_bdiv_q (qp, wp, np, nn, dp, dn, dinv);
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return;
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}
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/* use bdiv_qr for bottom portion */
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/* use sb_bdiv_q or dc_bdiv_q for top portion */
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}
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