54 lines
1.7 KiB
C
54 lines
1.7 KiB
C
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/*=============================================================================
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This file is part of FLINT.
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FLINT 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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FLINT 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 FLINT; 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) 2013 Mike Hansen
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******************************************************************************/
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#include "fq_zech.h"
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void
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fq_zech_sub(fq_zech_t rop, const fq_zech_t op1, const fq_zech_t op2,
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const fq_zech_ctx_t ctx)
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{
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mp_limb_t index, c;
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if (op2->value == ctx->qm1)
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{
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rop->value = op1->value;
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}
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else if (op1->value == ctx->qm1)
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{
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fq_zech_neg(rop, op2, ctx);
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}
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else
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{
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index = n_submod(op2->value, op1->value, ctx->qm1);
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index = n_submod(index, ctx->qm1o2, ctx->qm1);
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c = ctx->zech_log_table[index];
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if (c != ctx->qm1)
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{
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c = n_addmod(c, op1->value, ctx->qm1);
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}
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rop->value = c;
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}
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}
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