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https://github.com/vale981/arb
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41 lines
1 KiB
C
41 lines
1 KiB
C
/*
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Copyright (C) 2016 Pascal Molin
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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 "dirichlet.h"
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/* order of an element knowing the factorization of a multiple */
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ulong
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nmod_order_precomp(ulong a, nmod_t mod, ulong expo, n_factor_t fac)
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{
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int k;
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ulong pe, ap, order = 1;
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for (k = 0; k < fac.num; k++)
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{
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pe = n_pow(fac.p[k], fac.exp[k]);
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ap = nmod_pow_ui(a, expo / pe, mod);
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while ( ap != 1)
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{
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ap = nmod_pow_ui(ap, fac.p[k], mod);
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order *= fac.p[k];
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}
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}
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return order;
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}
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ulong
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dirichlet_order_ui(const dirichlet_group_t G, ulong a)
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{
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n_factor_t fac;
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n_factor_init(&fac);
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n_factor(&fac, G->expo, 1);
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return nmod_order_precomp(a, G->mod, G->expo, fac);
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}
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