72 lines
2.3 KiB
C
72 lines
2.3 KiB
C
/* mpn_mulmid_n -- balanced middle product
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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 "mpir.h"
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#include "gmp-impl.h"
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/*
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Let a = sum_0^{m-1} a_i B^i and b = sum_0^{n-1} b_j B^j
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then MP(a, m, b, n) = sum_{0<=i<m, 0<=j<n, n-1<=i+j<=m-1} a_ib_j B^{i+j-n+1}
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Note there are m-n+1 different values of i+j and each product a_ib_j will be two limbs. Thus when added together, the sum must take up n-m+3 limbs of space.
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This function computes MP(ap,2n-1,bp,n)
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It is required that n << GMP_NUMBMAX.
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*/
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void
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mpn_mulmid_n (mp_ptr rp, mp_srcptr ap, mp_srcptr bp, mp_size_t n)
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{
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ASSERT (n >= 1);
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ASSERT (! MPN_OVERLAP_P (rp, n + 2, ap, 2*n - 1));
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ASSERT (! MPN_OVERLAP_P (rp, n + 2, bp, n));
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if (n < MULMID_TOOM42_THRESHOLD)
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{
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mpn_mulmid_basecase (rp, ap, 2*n - 1, bp, n);
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}
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else
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{
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mp_size_t k;
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mp_ptr scratch;
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TMP_DECL;
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k = mpn_toom42_mulmid_itch (n);
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if (k <= 1000) k = 1000;
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TMP_MARK;
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scratch = TMP_ALLOC_LIMBS (k);
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mpn_toom42_mulmid (rp, ap, bp, n, scratch);
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TMP_FREE;
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}
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}
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