147 lines
4.0 KiB
C
147 lines
4.0 KiB
C
/*============================================================================
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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) 2011, 2012 Sebastian Pancratz
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******************************************************************************/
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#include "fmpz_mod_poly.h"
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#include "padic_poly.h"
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void _padic_poly_sub(fmpz *rop, slong *val, slong N,
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const fmpz *op1, slong val1, slong len1, slong N1,
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const fmpz *op2, slong val2, slong len2, slong N2,
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const padic_ctx_t ctx)
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{
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const slong len = FLINT_MAX(len1, len2);
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*val = FLINT_MIN(val1, val2);
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if (val1 == val2)
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{
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_fmpz_poly_sub(rop, op1, len1, op2, len2);
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_padic_poly_canonicalise(rop, val, len, ctx->p);
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}
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else
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{
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fmpz_t x;
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fmpz_init(x);
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if (val1 < val2) /* F := p^g (G - p^{h-g} H) */
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{
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fmpz_pow_ui(x, ctx->p, val2 - val1);
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if (rop == op1)
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{
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_fmpz_vec_zero(rop + len1, len2 - len1);
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_fmpz_vec_scalar_submul_fmpz(rop, op2, len2, x);
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}
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else
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{
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_fmpz_vec_scalar_mul_fmpz(rop, op2, len2, x);
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_fmpz_vec_neg(rop, rop, len2);
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_fmpz_poly_add(rop, op1, len1, rop, len2);
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}
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}
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else /* F := p^h (p^(g-h) G - H) */
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{
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fmpz_pow_ui(x, ctx->p, val1 - val2);
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if (rop == op2)
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{
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_fmpz_vec_neg(rop, op2, len2);
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_fmpz_vec_zero(rop + len2, len1 - len2);
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_fmpz_vec_scalar_addmul_fmpz(rop, op1, len1, x);
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}
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else
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{
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_fmpz_vec_scalar_mul_fmpz(rop, op1, len1, x);
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_fmpz_poly_sub(rop, rop, len1, op2, len2);
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}
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}
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fmpz_clear(x);
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}
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/* Reduce */
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if (N - *val > 0)
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{
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fmpz_t pow;
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int alloc;
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alloc = _padic_ctx_pow_ui(pow, N - *val, ctx);
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if (N >= N1 && N >= N2)
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{
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slong i;
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for (i = 0; i < len; i++)
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if (fmpz_sgn(rop + i) < 0)
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fmpz_add(rop + i, rop + i, pow);
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}
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else
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{
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_fmpz_vec_scalar_mod_fmpz(rop, rop, len, pow);
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}
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if (alloc)
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fmpz_clear(pow);
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}
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else
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{
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_fmpz_vec_zero(rop, len);
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*val = 0;
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}
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}
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void padic_poly_sub(padic_poly_t f,
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const padic_poly_t g, const padic_poly_t h,
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const padic_ctx_t ctx)
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{
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const slong lenG = g->length;
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const slong lenH = h->length;
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const slong lenF = FLINT_MAX(lenG, lenH);
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if (lenG == 0)
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{
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padic_poly_neg(f, h, ctx);
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return;
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}
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if (lenH == 0)
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{
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padic_poly_set(f, g, ctx);
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return;
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}
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if ((lenG == 0 && lenH == 0) || (FLINT_MIN(g->val, h->val) >= f->N))
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{
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padic_poly_zero(f);
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return;
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}
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padic_poly_fit_length(f, lenF);
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_padic_poly_sub(f->coeffs, &(f->val), f->N,
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g->coeffs, g->val, lenG, g->N,
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h->coeffs, h->val, lenH, h->N, ctx);
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_padic_poly_set_length(f, lenF);
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_padic_poly_normalise(f);
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}
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