100 lines
2.8 KiB
C
100 lines
2.8 KiB
C
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/* mpn_sub_err2_n -- sub_n with two error terms
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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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#include "gmp.h"
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#include "gmp-impl.h"
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/*
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Same as mpn_sub_err1_n, but computes both
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c[1]*yp1[n-1] + ... + c[n]*yp1[0]
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and c[1]*yp2[n-1] + ... + c[n]*yp2[0],
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storing results at {ep,2}, {ep+2,2} respectively.
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*/
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mp_limb_t
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mpn_sub_err2_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp,
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mp_ptr ep, mp_srcptr yp1, mp_srcptr yp2,
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mp_size_t n, mp_limb_t cy)
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{
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mp_limb_t el1, eh1, el2, eh2, ul, vl, yl1, yl2, zl1, zl2, rl, sl, cy1, cy2;
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ASSERT (n >= 1);
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ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
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ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n));
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ASSERT (MPN_SAME_OR_SEPARATE_P (rp, yp, n));
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/* FIXME: first addition into eh:el is redundant */
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yp1 += n - 1;
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yp2 += n - 1;
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el1 = eh1 = 0;
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el2 = eh2 = 0;
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do
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{
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yl1 = *yp1--;
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yl2 = *yp2--;
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ul = *up++;
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vl = *vp++;
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/* ordinary sub_n */
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SUBC_LIMB (cy1, sl, ul, vl);
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SUBC_LIMB (cy2, rl, sl, cy);
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cy = cy1 | cy2;
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*rp++ = rl;
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/* update (eh1:el1) */
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zl1 = cy ? yl1 : 0;
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el1 += zl1;
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eh1 += el1 < zl1;
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/* update (eh2:el2) */
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zl2 = cy ? yl2 : 0;
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el2 += zl2;
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eh2 += el2 < zl2;
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}
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while (--n != 0);
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#if GMP_NAIL_BITS != 0
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eh1 = (eh1 << GMP_NAIL_BITS) + (el1 >> GMP_NUMB_BITS);
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el1 &= GMP_NUMB_MASK;
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eh2 = (eh2 << GMP_NAIL_BITS) + (el2 >> GMP_NUMB_BITS);
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el2 &= GMP_NUMB_MASK;
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#endif
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ep[0] = el1;
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ep[1] = eh1;
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ep[2] = el2;
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ep[3] = eh2;
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return cy;
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}
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