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https://github.com/vale981/arb
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49 lines
1.2 KiB
C
49 lines
1.2 KiB
C
/*
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Copyright (C) 2018 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_mat.h"
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void
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_arb_mat_companion(arb_mat_t A, arb_srcptr poly, slong prec)
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{
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slong i, j, n;
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arb_t c;
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n = arb_mat_nrows(A);
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if (n == 0)
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return;
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for (i = 0; i < n - 1; i++)
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for (j = 0; j < n; j++)
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arb_set_ui(arb_mat_entry(A, i, j), (i + 1) == j);
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arb_init(c);
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arb_inv(c, poly + n, prec);
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arb_neg(c, c);
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for (j = 0; j < n; j++)
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arb_mul(arb_mat_entry(A, n - 1, j), poly + j, c, prec);
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arb_clear(c);
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}
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void
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arb_mat_companion(arb_mat_t A, const arb_poly_t poly, slong prec)
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{
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slong n = arb_mat_nrows(A);
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if (n != arb_poly_degree(poly) || n != arb_mat_ncols(A))
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{
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flint_printf("arb_mat_companion: incompatible dimensions!\n");
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flint_abort();
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}
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_arb_mat_companion(A, poly->coeffs, prec);
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}
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