254 lines
6.9 KiB
C
254 lines
6.9 KiB
C
/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2010, 2011 William Hart
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Copyright (C) 2011 Sebastian Pancratz
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******************************************************************************/
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#include <stdlib.h>
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#include <gmp.h>
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#include "flint.h"
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#include "nmod_vec.h"
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#include "nmod_poly.h"
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#include "ulong_extras.h"
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void
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_nmod_poly_divrem_basecase_1(mp_ptr Q, mp_ptr R, mp_ptr W,
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mp_srcptr A, slong lenA, mp_srcptr B, slong lenB,
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nmod_t mod)
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{
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const mp_limb_t invL = n_invmod(B[lenB - 1], mod.n);
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slong iR;
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mp_ptr ptrQ = Q - lenB + 1;
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mp_ptr R1 = W;
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flint_mpn_copyi(R1, A, lenA);
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for (iR = lenA - 1; iR >= lenB - 1; iR--)
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{
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if (R1[iR] == 0)
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{
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ptrQ[iR] = WORD(0);
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}
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else
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{
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ptrQ[iR] = n_mulmod2_preinv(R1[iR], invL, mod.n, mod.ninv);
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if (lenB > 1)
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{
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const mp_limb_t c = n_negmod(ptrQ[iR], mod.n);
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mpn_addmul_1(R1 + iR - lenB + 1, B, lenB - 1, c);
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}
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}
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}
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if (lenB > 1)
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_nmod_vec_reduce(R, R1, lenB - 1, mod);
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}
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void
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_nmod_poly_divrem_basecase_2(mp_ptr Q, mp_ptr R, mp_ptr W,
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mp_srcptr A, slong lenA, mp_srcptr B, slong lenB,
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nmod_t mod)
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{
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const mp_limb_t invL = n_invmod(B[lenB - 1], mod.n);
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slong iR, i;
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mp_ptr B2 = W, R2 = W + 2*(lenB - 1), ptrQ = Q - lenB + 1;
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for (i = 0; i < lenB - 1; i++)
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{
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B2[2 * i] = B[i];
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B2[2 * i + 1] = 0;
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}
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for (i = 0; i < lenA; i++)
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{
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R2[2 * i] = A[i];
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R2[2 * i + 1] = 0;
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}
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for (iR = lenA - 1; iR >= lenB - 1; )
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{
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mp_limb_t r =
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n_ll_mod_preinv(R2[2 * iR + 1], R2[2 * iR], mod.n, mod.ninv);
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while ((iR + 1 >= lenB) && (r == WORD(0)))
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{
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ptrQ[iR--] = WORD(0);
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if (iR + 1 >= lenB)
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r = n_ll_mod_preinv(R2[2 * iR + 1], R2[2 * iR], mod.n,
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mod.ninv);
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}
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if (iR + 1 >= lenB)
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{
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ptrQ[iR] = n_mulmod2_preinv(r, invL, mod.n, mod.ninv);
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if (lenB > 1)
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{
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const mp_limb_t c = n_negmod(ptrQ[iR], mod.n);
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mpn_addmul_1(R2 + 2 * (iR - lenB + 1), B2, 2 * lenB - 2, c);
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}
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iR--;
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}
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}
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for (iR = 0; iR < lenB - 1; iR++)
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R[iR] = n_ll_mod_preinv(R2[2*iR+1], R2[2*iR], mod.n, mod.ninv);
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}
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void
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_nmod_poly_divrem_basecase_3(mp_ptr Q, mp_ptr R, mp_ptr W,
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mp_srcptr A, slong lenA, mp_srcptr B, slong lenB,
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nmod_t mod)
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{
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const mp_limb_t invL = n_invmod(B[lenB - 1], mod.n);
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slong iR, i;
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mp_ptr B3 = W, R3 = W + 3*(lenB - 1), ptrQ = Q - lenB + 1;
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for (i = 0; i < lenB - 1; i++)
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{
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B3[3 * i] = B[i];
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B3[3 * i + 1] = 0;
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B3[3 * i + 2] = 0;
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}
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for (i = 0; i < lenA; i++)
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{
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R3[3 * i] = A[i];
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R3[3 * i + 1] = 0;
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R3[3 * i + 2] = 0;
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}
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for (iR = lenA - 1; iR >= lenB - 1; )
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{
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mp_limb_t r =
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n_lll_mod_preinv(R3[3 * iR + 2], R3[3 * iR + 1],
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R3[3 * iR], mod.n, mod.ninv);
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while ((iR + 1 >= lenB) && (r == WORD(0)))
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{
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ptrQ[iR--] = WORD(0);
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if (iR + 1 >= lenB)
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r = n_lll_mod_preinv(R3[3 * iR + 2], R3[3 * iR + 1],
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R3[3 * iR], mod.n, mod.ninv);
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}
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if (iR + 1 >= lenB)
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{
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ptrQ[iR] = n_mulmod2_preinv(r, invL, mod.n, mod.ninv);
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if (lenB > 1)
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{
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const mp_limb_t c = n_negmod(ptrQ[iR], mod.n);
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mpn_addmul_1(R3 + 3 * (iR - lenB + 1), B3, 3 * lenB - 3, c);
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}
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iR--;
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}
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}
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for (iR = 0; iR < lenB - 1; iR++)
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R[iR] = n_lll_mod_preinv(R3[3 * iR + 2], R3[3 * iR + 1],
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R3[3 * iR], mod.n, mod.ninv);
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}
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void
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_nmod_poly_divrem_basecase(mp_ptr Q, mp_ptr R, mp_ptr W,
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mp_srcptr A, slong lenA, mp_srcptr B, slong lenB,
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nmod_t mod)
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{
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const slong bits =
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2 * (FLINT_BITS - mod.norm) + FLINT_BIT_COUNT(lenA - lenB + 1);
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if (bits <= FLINT_BITS)
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_nmod_poly_divrem_basecase_1(Q, R, W, A, lenA, B, lenB, mod);
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else if (bits <= 2 * FLINT_BITS)
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_nmod_poly_divrem_basecase_2(Q, R, W, A, lenA, B, lenB, mod);
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else
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_nmod_poly_divrem_basecase_3(Q, R, W, A, lenA, B, lenB, mod);
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}
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void
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nmod_poly_divrem_basecase(nmod_poly_t Q, nmod_poly_t R, const nmod_poly_t A,
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const nmod_poly_t B)
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{
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const slong lenA = A->length, lenB = B->length;
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mp_ptr Q_coeffs, R_coeffs, W;
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nmod_poly_t t1, t2;
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TMP_INIT;
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if (lenB == 0)
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{
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flint_printf("Exception (nmod_poly_divrem). Division by zero.\n");
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abort();
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}
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if (lenA < lenB)
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{
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nmod_poly_set(R, A);
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nmod_poly_zero(Q);
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return;
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}
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if (Q == A || Q == B)
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{
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nmod_poly_init2_preinv(t1, B->mod.n, B->mod.ninv, lenA - lenB + 1);
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Q_coeffs = t1->coeffs;
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}
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else
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{
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nmod_poly_fit_length(Q, lenA - lenB + 1);
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Q_coeffs = Q->coeffs;
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}
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if (R == A || R == B)
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{
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nmod_poly_init2_preinv(t2, B->mod.n, B->mod.ninv, lenB - 1);
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R_coeffs = t2->coeffs;
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}
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else
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{
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nmod_poly_fit_length(R, lenB - 1);
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R_coeffs = R->coeffs;
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}
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TMP_START;
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W = TMP_ALLOC(NMOD_DIVREM_BC_ITCH(lenA, lenB, A->mod)*sizeof(mp_limb_t));
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_nmod_poly_divrem_basecase(Q_coeffs, R_coeffs, W, A->coeffs, lenA,
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B->coeffs, lenB, B->mod);
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if (Q == A || Q == B)
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{
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nmod_poly_swap(Q, t1);
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nmod_poly_clear(t1);
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}
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if (R == A || R == B)
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{
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nmod_poly_swap(R, t2);
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nmod_poly_clear(t2);
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}
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Q->length = lenA - lenB + 1;
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R->length = lenB - 1;
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TMP_END;
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_nmod_poly_normalise(R);
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}
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