mirror of
https://github.com/vale981/arb
synced 2025-03-04 17:01:40 -05:00
113 lines
2.7 KiB
C
113 lines
2.7 KiB
C
/*
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Copyright (C) 2012, 2013 Fredrik Johansson
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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 it under
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the terms of the GNU Lesser General Public License (LGPL) as published
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by the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version. See <http://www.gnu.org/licenses/>.
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*/
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#include "arb_poly.h"
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void
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_arb_poly_div_series(arb_ptr Q, arb_srcptr A, slong Alen,
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arb_srcptr B, slong Blen, slong n, slong prec)
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{
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Alen = FLINT_MIN(Alen, n);
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Blen = FLINT_MIN(Blen, n);
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if (Blen == 1)
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{
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_arb_vec_scalar_div(Q, A, Alen, B, prec);
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_arb_vec_zero(Q + Alen, n - Alen);
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}
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else if (n == 2)
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{
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if (Alen == 1)
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{
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arb_div(Q, A, B, prec);
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arb_div(Q + 1, Q, B, prec);
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arb_mul(Q + 1, Q + 1, B + 1, prec);
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arb_neg(Q + 1, Q + 1);
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}
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else
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{
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arb_div(Q, A, B, prec);
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arb_mul(Q + 1, Q, B + 1, prec);
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arb_sub(Q + 1, A + 1, Q + 1, prec);
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arb_div(Q + 1, Q + 1, B, prec);
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}
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}
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else if (Blen == 2 || n <= 10)
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{
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/* The basecase algorithm is faster for much larger Blen and n than
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this, but unfortunately has worse numerical stability. */
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slong i;
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arb_t q;
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arb_init(q);
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arb_inv(q, B, prec);
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arb_div(Q, A, B, prec);
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for (i = 1; i < n; i++)
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{
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arb_dot(Q + i, (i < Alen) ? A + i : NULL, 1,
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B + 1, 1, Q + i - 1, -1, FLINT_MIN(i, Blen - 1), prec);
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if (!arb_is_one(q))
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arb_mul(Q + i, Q + i, q, prec);
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}
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arb_clear(q);
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}
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else
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{
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arb_ptr Binv;
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Binv = _arb_vec_init(n);
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_arb_poly_inv_series(Binv, B, Blen, n, prec);
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_arb_poly_mullow(Q, Binv, n, A, Alen, n, prec);
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_arb_vec_clear(Binv, n);
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}
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}
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void
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arb_poly_div_series(arb_poly_t Q, const arb_poly_t A, const arb_poly_t B, slong n, slong prec)
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{
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if (n == 0)
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{
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arb_poly_zero(Q);
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return;
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}
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if (B->length == 0)
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{
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arb_poly_fit_length(Q, n);
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_arb_vec_indeterminate(Q->coeffs, n);
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_arb_poly_set_length(Q, n);
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return;
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}
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if (A->length == 0)
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{
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arb_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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arb_poly_t t;
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arb_poly_init(t);
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arb_poly_div_series(t, A, B, n, prec);
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arb_poly_swap(Q, t);
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arb_poly_clear(t);
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return;
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}
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arb_poly_fit_length(Q, n);
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_arb_poly_div_series(Q->coeffs, A->coeffs, A->length, B->coeffs, B->length, n, prec);
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_arb_poly_set_length(Q, n);
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_arb_poly_normalise(Q);
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}
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