mirror of
https://github.com/vale981/arb
synced 2025-03-06 01:41:39 -05:00
52 lines
1.3 KiB
C
52 lines
1.3 KiB
C
/*
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Copyright (C) 2021 Matthias Gessinger
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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_graeffe_transform(arb_ptr b, arb_srcptr a, slong len, slong prec)
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{
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if (len == 0)
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return;
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slong q, i;
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q = (len-1)/2+1;
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arb_ptr pe = _arb_vec_init(q);
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arb_ptr po = _arb_vec_init(len);
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for (i = len-1; i >= 0; i--)
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{
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if (i % 2 == 0)
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arb_set(pe+i/2, a+i);
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else
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arb_set(po+i/2, a+i);
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}
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_arb_poly_mul(b, po, q, po, q, prec);
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_arb_poly_shift_left(b, b, len-1, 1);
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_arb_poly_mul(po, pe, q, pe, q, prec);
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_arb_vec_sub(b, po, b, len, prec);
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_arb_vec_clear(pe, q);
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_arb_vec_clear(po, len);
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if (len % 2 == 0)
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_arb_vec_neg(b, b, len);
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}
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void
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arb_poly_graeffe_transform(arb_poly_t b, const arb_poly_t a, slong prec)
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{
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arb_poly_fit_length(b, a->length);
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_arb_poly_graeffe_transform(b->coeffs, a->coeffs, a->length, prec);
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_arb_poly_set_length(b, a->length);
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}
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