272 lines
6.9 KiB
C
272 lines
6.9 KiB
C
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/*=============================================================================
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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) 2011 William Hart
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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_div_basecase_1(mp_ptr Q, mp_ptr W,
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mp_srcptr A, slong A_len, mp_srcptr B, slong B_len,
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nmod_t mod)
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{
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mp_limb_t lead_inv = n_invmod(B[B_len - 1], mod.n);
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slong len, coeff = A_len - B_len;
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mp_ptr R1 = W;
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mp_srcptr Btop = B + B_len - 1;
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flint_mpn_copyi(R1, A + B_len - 1, A_len - B_len + 1);
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while (coeff >= 0)
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{
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R1[coeff] = n_mod2_preinv(R1[coeff], mod.n, mod.ninv);
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while (coeff >= 0 && R1[coeff] == WORD(0))
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{
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Q[coeff--] = WORD(0);
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if (coeff >= 0)
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R1[coeff] = n_mod2_preinv(R1[coeff], mod.n, mod.ninv);
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}
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if (coeff >= 0)
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{
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mp_limb_t c, * R_sub;
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Q[coeff] =
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n_mulmod2_preinv(R1[coeff], lead_inv, mod.n, mod.ninv);
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c = n_negmod(Q[coeff], mod.n);
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len = FLINT_MIN(B_len - 1, coeff);
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R_sub = R1 + coeff - len;
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if (len > 0)
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mpn_addmul_1(R_sub, Btop - len, len, c);
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coeff--;
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}
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}
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}
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void
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_nmod_poly_div_basecase_2(mp_ptr Q, mp_ptr W,
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mp_srcptr A, slong A_len, mp_srcptr B, slong B_len,
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nmod_t mod)
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{
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slong coeff, i, len;
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mp_limb_t lead_inv = n_invmod(B[B_len - 1], mod.n);
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mp_ptr B2, R2;
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mp_srcptr Btop;
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B2 = W;
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for (i = 0; i < B_len - 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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Btop = B2 + 2*(B_len - 1);
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R2 = W + 2*(B_len - 1);
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for (i = 0; i < A_len - B_len + 1; i++)
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{
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R2[2 * i] = A[B_len + i - 1];
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R2[2 * i + 1] = 0;
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}
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coeff = A_len - B_len;
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while (coeff >= 0)
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{
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mp_limb_t r_coeff;
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r_coeff =
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n_ll_mod_preinv(R2[2 * coeff + 1], R2[2 * coeff], mod.n, mod.ninv);
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while (coeff >= 0 && r_coeff == WORD(0))
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{
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Q[coeff--] = WORD(0);
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if (coeff >= 0)
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r_coeff =
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n_ll_mod_preinv(R2[2 * coeff + 1], R2[2 * coeff], mod.n,
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mod.ninv);
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}
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if (coeff >= 0)
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{
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mp_limb_t c, * R_sub;
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Q[coeff] =
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n_mulmod2_preinv(r_coeff, lead_inv, mod.n, mod.ninv);
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c = n_negmod(Q[coeff], mod.n);
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len = FLINT_MIN(B_len - 1, coeff);
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R_sub = R2 + 2 * (coeff - len);
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if (len > 0)
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mpn_addmul_1(R_sub, Btop - 2*len, 2 * len, c);
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coeff--;
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}
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}
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}
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void
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_nmod_poly_div_basecase_3(mp_ptr Q, mp_ptr W,
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mp_srcptr A, slong A_len, mp_srcptr B, slong B_len,
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nmod_t mod)
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{
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slong coeff, i, len;
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mp_limb_t lead_inv = n_invmod(B[B_len - 1], mod.n);
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mp_limb_t r_coeff;
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mp_ptr B3, R3;
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mp_srcptr Btop;
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B3 = W;
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for (i = 0; i < B_len - 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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Btop = B3 + 3*(B_len - 1);
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R3 = W + 3*(B_len - 1);
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for (i = 0; i < A_len - B_len + 1; i++)
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{
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R3[3 * i] = A[B_len + i - 1];
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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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coeff = A_len - B_len;
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while (coeff >= 0)
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{
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r_coeff =
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n_lll_mod_preinv(R3[3 * coeff + 2], R3[3 * coeff + 1],
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R3[3 * coeff], mod.n, mod.ninv);
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while (coeff >= 0 && r_coeff == WORD(0))
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{
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Q[coeff--] = WORD(0);
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if (coeff >= 0)
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r_coeff =
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n_lll_mod_preinv(R3[3 * coeff + 2], R3[3 * coeff + 1],
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R3[3 * coeff], mod.n, mod.ninv);
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}
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if (coeff >= 0)
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{
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mp_limb_t c, * R_sub;
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Q[coeff] =
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n_mulmod2_preinv(r_coeff, lead_inv, mod.n, mod.ninv);
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c = n_negmod(Q[coeff], mod.n);
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len = FLINT_MIN(B_len - 1, coeff);
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R_sub = R3 + 3 * (coeff - len);
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if (len > 0)
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mpn_addmul_1(R_sub, Btop - 3*len, 3 * len, c);
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coeff--;
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}
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}
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}
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void
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_nmod_poly_div_basecase(mp_ptr Q, mp_ptr W,
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mp_srcptr A, slong A_len, mp_srcptr B, slong B_len,
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nmod_t mod)
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{
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slong bits =
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2 * (FLINT_BITS - mod.norm) + FLINT_BIT_COUNT(A_len - B_len + 1);
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if (bits <= FLINT_BITS)
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_nmod_poly_div_basecase_1(Q, W, A, A_len, B, B_len, mod);
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else if (bits <= 2 * FLINT_BITS)
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_nmod_poly_div_basecase_2(Q, W, A, A_len, B, B_len, mod);
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else
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_nmod_poly_div_basecase_3(Q, W, A, A_len, B, B_len, mod);
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}
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void
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nmod_poly_div_basecase(nmod_poly_t Q, const nmod_poly_t A,
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const nmod_poly_t B)
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{
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mp_ptr Q_coeffs, W;
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nmod_poly_t t1;
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slong Alen, Blen;
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TMP_INIT;
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Blen = B->length;
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if (Blen == 0)
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{
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flint_printf("Exception (nmod_poly_div_base). Division by zero.\n");
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abort();
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}
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Alen = A->length;
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if (Alen < Blen)
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{
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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,
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Alen - Blen + 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, Alen - Blen + 1);
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Q_coeffs = Q->coeffs;
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}
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TMP_START;
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W = TMP_ALLOC(NMOD_DIV_BC_ITCH(Alen, Blen, A->mod)*sizeof(mp_limb_t));
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_nmod_poly_div_basecase(Q_coeffs, W, A->coeffs, Alen,
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B->coeffs, Blen, 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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Q->length = Alen - Blen + 1;
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TMP_END;
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_nmod_poly_normalise(Q);
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}
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