mirror of
https://github.com/vale981/arb
synced 2025-03-05 09:21:38 -05:00
135 lines
3.8 KiB
C
135 lines
3.8 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 "arb_poly.h"
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#include "arb_mat.h"
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void
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_arb_poly_compose_series_brent_kung(arb_ptr res,
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arb_srcptr poly1, slong len1,
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arb_srcptr poly2, slong len2, slong n, slong prec)
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{
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arb_mat_t A, B, C;
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arb_ptr t, h;
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slong i, m;
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if (n == 1)
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{
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arb_set(res, poly1);
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return;
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}
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m = n_sqrt(n) + 1;
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arb_mat_init(A, m, n);
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arb_mat_init(B, m, m);
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arb_mat_init(C, m, n);
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h = _arb_vec_init(n);
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t = _arb_vec_init(n);
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/* Set rows of B to the segments of poly1 */
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for (i = 0; i < len1 / m; i++)
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_arb_vec_set(B->rows[i], poly1 + i*m, m);
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_arb_vec_set(B->rows[i], poly1 + i*m, len1 % m);
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/* Set rows of A to powers of poly2 */
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arb_set_ui(A->rows[0] + 0, UWORD(1));
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_arb_vec_set(A->rows[1], poly2, len2);
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for (i = 2; i < m; i++)
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_arb_poly_mullow(A->rows[i], A->rows[(i + 1) / 2], n, A->rows[i / 2], n, n, prec);
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arb_mat_mul(C, B, A, prec);
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/* Evaluate block composition using the Horner scheme */
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_arb_vec_set(res, C->rows[m - 1], n);
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_arb_poly_mullow(h, A->rows[m - 1], n, poly2, len2, n, prec);
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for (i = m - 2; i >= 0; i--)
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{
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_arb_poly_mullow(t, res, n, h, n, n, prec);
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_arb_poly_add(res, t, n, C->rows[i], n, prec);
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}
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_arb_vec_clear(h, n);
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_arb_vec_clear(t, n);
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arb_mat_clear(A);
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arb_mat_clear(B);
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arb_mat_clear(C);
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}
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void
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arb_poly_compose_series_brent_kung(arb_poly_t res,
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const arb_poly_t poly1,
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const arb_poly_t poly2, slong n, slong prec)
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{
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slong len1 = poly1->length;
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slong len2 = poly2->length;
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slong lenr;
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if (len2 != 0 && !arb_is_zero(poly2->coeffs))
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{
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flint_printf("exception: compose_series: inner "
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"polynomial must have zero constant term\n");
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abort();
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}
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if (len1 == 0 || n == 0)
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{
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arb_poly_zero(res);
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return;
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}
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if (len2 == 0 || len1 == 1)
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{
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arb_poly_set_arb(res, poly1->coeffs);
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return;
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}
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lenr = FLINT_MIN((len1 - 1) * (len2 - 1) + 1, n);
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len1 = FLINT_MIN(len1, lenr);
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len2 = FLINT_MIN(len2, lenr);
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if ((res != poly1) && (res != poly2))
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{
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arb_poly_fit_length(res, lenr);
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_arb_poly_compose_series_brent_kung(res->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2, lenr, prec);
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_arb_poly_set_length(res, lenr);
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_arb_poly_normalise(res);
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}
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else
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{
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arb_poly_t t;
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arb_poly_init2(t, lenr);
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_arb_poly_compose_series_brent_kung(t->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2, lenr, prec);
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_arb_poly_set_length(t, lenr);
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_arb_poly_normalise(t);
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arb_poly_swap(res, t);
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arb_poly_clear(t);
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}
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}
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