mirror of
https://github.com/vale981/arb
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127 lines
3.4 KiB
C
127 lines
3.4 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 "acb_mat.h"
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void
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acb_mat_exp_taylor_sum(acb_mat_t S, const acb_mat_t A, slong N, slong prec)
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{
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if (A == S)
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{
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acb_mat_t t;
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acb_mat_init(t, acb_mat_nrows(A), acb_mat_nrows(A));
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acb_mat_set(t, A);
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acb_mat_exp_taylor_sum(S, t, N, prec);
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acb_mat_clear(t);
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}
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else if (N <= 0)
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{
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acb_mat_zero(S);
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}
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else if (N == 1)
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{
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acb_mat_one(S);
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}
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else if (N == 2)
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{
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acb_mat_one(S);
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acb_mat_add(S, S, A, prec);
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}
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else if (N == 3)
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{
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acb_mat_t T;
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acb_mat_init(T, acb_mat_nrows(A), acb_mat_nrows(A));
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acb_mat_sqr(T, A, prec);
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acb_mat_scalar_mul_2exp_si(T, T, -1);
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acb_mat_add(S, A, T, prec);
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acb_mat_one(T);
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acb_mat_add(S, S, T, prec);
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acb_mat_clear(T);
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}
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else
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{
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slong i, lo, hi, m, w, dim;
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acb_mat_struct * pows;
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acb_mat_t T, U;
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fmpz_t c, f;
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dim = acb_mat_nrows(A);
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m = n_sqrt(N);
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w = (N + m - 1) / m;
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fmpz_init(c);
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fmpz_init(f);
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pows = flint_malloc(sizeof(acb_mat_t) * (m + 1));
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acb_mat_init(T, dim, dim);
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acb_mat_init(U, dim, dim);
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for (i = 0; i <= m; i++)
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{
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acb_mat_init(pows + i, dim, dim);
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if (i == 0)
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acb_mat_one(pows + i);
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else if (i == 1)
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acb_mat_set(pows + i, A);
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else
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acb_mat_mul(pows + i, pows + i - 1, A, prec);
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}
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acb_mat_zero(S);
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fmpz_one(f);
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for (i = w - 1; i >= 0; i--)
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{
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lo = i * m;
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hi = FLINT_MIN(N - 1, lo + m - 1);
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acb_mat_zero(T);
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fmpz_one(c);
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while (hi >= lo)
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{
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acb_mat_scalar_addmul_fmpz(T, pows + hi - lo, c, prec);
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if (hi != 0)
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fmpz_mul_ui(c, c, hi);
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hi--;
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}
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acb_mat_mul(U, pows + m, S, prec);
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acb_mat_scalar_mul_fmpz(S, T, f, prec);
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acb_mat_add(S, S, U, prec);
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fmpz_mul(f, f, c);
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}
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acb_mat_scalar_div_fmpz(S, S, f, prec);
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fmpz_clear(c);
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fmpz_clear(f);
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for (i = 0; i <= m; i++)
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acb_mat_clear(pows + i);
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flint_free(pows);
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acb_mat_clear(T);
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acb_mat_clear(U);
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}
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}
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