mirror of
https://github.com/vale981/arb
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66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
/*=============================================================================
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This file is part of ARB.
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ARB 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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ARB 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 ARB; 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) 2012 Fredrik Johansson
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******************************************************************************/
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#include "fmpz_holonomic.h"
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mp_limb_t
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fmpz_holonomic_get_nth_nmod(const fmpz_holonomic_t op, mp_srcptr initial, ulong n0, ulong n, nmod_t mod)
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{
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long r = fmpz_holonomic_order(op);
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if (r == 0)
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{
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return 0;
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}
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else if (n < n0)
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{
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printf("not implemented\n");
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abort();
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}
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else if (n - n0 < r)
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{
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return initial[n - n0];
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}
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else
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{
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nmod_mat_t M;
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long i;
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mp_limb_t t, Q;
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nmod_mat_init(M, r, r, mod.n);
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fmpz_holonomic_forward_nmod_mat(M, &Q, op, n0, n - n0 - r + 1);
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t = 0;
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for (i = 0; i < r; i++)
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{
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NMOD_ADDMUL(t, M->rows[r - 1][i], initial[i], mod);
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}
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t = n_mulmod2_preinv(t, n_invmod(Q, mod.n), mod.n, mod.ninv);
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nmod_mat_clear(M);
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return t;
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}
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}
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