mirror of
https://github.com/vale981/arb
synced 2025-03-04 17:01:40 -05:00
50 lines
1.2 KiB
C
50 lines
1.2 KiB
C
/*
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Copyright (C) 2014 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 "acb_modular.h"
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void
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psl2z_randtest(psl2z_t g, flint_rand_t state, slong bits)
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{
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bits = FLINT_MAX(bits, 1);
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fmpz_randtest(&g->a, state, bits);
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fmpz_randtest(&g->b, state, bits);
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if (fmpz_is_zero(&g->a) && fmpz_is_zero(&g->b))
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{
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psl2z_one(g);
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}
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else
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{
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fmpz_t t;
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fmpz_init(t);
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fmpz_xgcd(t, &g->d, &g->c, &g->a, &g->b);
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fmpz_divexact(&g->a, &g->a, t);
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fmpz_divexact(&g->b, &g->b, t);
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if (fmpz_sgn(&g->c) < 0)
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fmpz_neg(&g->c, &g->c);
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else
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fmpz_neg(&g->b, &g->b);
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if (fmpz_is_zero(&g->c) && fmpz_sgn(&g->d) < 0)
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{
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fmpz_neg(&g->a, &g->a);
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fmpz_neg(&g->b, &g->b);
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fmpz_neg(&g->c, &g->c);
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fmpz_neg(&g->d, &g->d);
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}
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fmpz_clear(t);
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}
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}
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