1 /*
2 Copyright (C) 2020 Daniel Schultz
3
4 This file is part of FLINT.
5
6 FLINT is free software: you can redistribute it and/or modify it under
7 the terms of the GNU Lesser General Public License (LGPL) as published
8 by the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version. See <https://www.gnu.org/licenses/>.
10 */
11
12 #include "fmpz_mod_mpoly.h"
13
14 /*
15 set A(x_var^Bstride[var]) to B/xbar^Bshifts
16 it is asserted that the conversion is correct
17 */
_fmpz_mod_mpoly_to_fmpz_mod_poly_deflate(fmpz_mod_poly_t A,const fmpz_mod_mpoly_t B,slong var,const ulong * Bshift,const ulong * Bstride,const fmpz_mod_mpoly_ctx_t ctx)18 void _fmpz_mod_mpoly_to_fmpz_mod_poly_deflate(
19 fmpz_mod_poly_t A,
20 const fmpz_mod_mpoly_t B,
21 slong var,
22 const ulong * Bshift,
23 const ulong * Bstride,
24 const fmpz_mod_mpoly_ctx_t ctx)
25 {
26 ulong mask;
27 slong i, shift, off, N;
28 slong len = B->length;
29 const fmpz * coeff = B->coeffs;
30 ulong * exp = B->exps;
31 ulong var_shift, var_stride;
32 flint_bitcnt_t bits = B->bits;
33
34 FLINT_ASSERT(len > 0);
35 FLINT_ASSERT(bits <= FLINT_BITS);
36
37 N = mpoly_words_per_exp_sp(bits, ctx->minfo);
38 mpoly_gen_offset_shift_sp(&off, &shift, var, bits, ctx->minfo);
39
40 fmpz_mod_poly_zero(A, ctx->ffinfo);
41 mask = (-UWORD(1)) >> (FLINT_BITS - bits);
42 var_shift = Bshift[var];
43 var_stride = Bstride[var];
44 for (i = 0; i < len; i++)
45 {
46 ulong k = (exp[N*i + off] >> shift) & mask;
47 FLINT_ASSERT(k >= var_shift);
48 k -= var_shift;
49 if (k != 0)
50 k /= var_stride;
51 fmpz_mod_poly_set_coeff_fmpz(A, k, coeff + i, ctx->ffinfo);
52 }
53
54 #if FLINT_WANT_ASSERT
55 for (i = 0; i < len; i++)
56 {
57 slong v;
58 for (v = 0; v < ctx->minfo->nvars; v++)
59 {
60 ulong k;
61 mpoly_gen_offset_shift_sp(&off, &shift, v, bits, ctx->minfo);
62 k = (exp[N*i + off] >> shift) & mask;
63 FLINT_ASSERT( (v == var && k >= Bshift[v])
64 || (v != var && k == Bshift[v]));
65 }
66 }
67 #endif
68 }
69
70 /*
71 set A to B(x_var^Astride[var])*xbar^Ashift
72 A must be packed into bits = Abits
73 */
_fmpz_mod_mpoly_from_fmpz_mod_poly_inflate(fmpz_mod_mpoly_t A,flint_bitcnt_t Abits,const fmpz_mod_poly_t B,slong var,const ulong * Ashift,const ulong * Astride,const fmpz_mod_mpoly_ctx_t ctx)74 void _fmpz_mod_mpoly_from_fmpz_mod_poly_inflate(
75 fmpz_mod_mpoly_t A,
76 flint_bitcnt_t Abits,
77 const fmpz_mod_poly_t B,
78 slong var,
79 const ulong * Ashift,
80 const ulong * Astride,
81 const fmpz_mod_mpoly_ctx_t ctx)
82 {
83 slong N;
84 slong k;
85 slong Alen;
86 fmpz * Acoeff;
87 ulong * Aexp;
88 ulong * shiftexp;
89 ulong * strideexp;
90 slong Bdeg = fmpz_mod_poly_degree(B, ctx->ffinfo);
91 TMP_INIT;
92
93 TMP_START;
94
95 FLINT_ASSERT(Abits <= FLINT_BITS);
96 FLINT_ASSERT(!fmpz_mod_poly_is_zero(B, ctx->ffinfo));
97
98 /* must have at least space for the highest exponent of var */
99 FLINT_ASSERT(1 + FLINT_BIT_COUNT(Ashift[var] + Bdeg*Astride[var]) <= Abits);
100
101 N = mpoly_words_per_exp_sp(Abits, ctx->minfo);
102 strideexp = (ulong*) TMP_ALLOC(N*sizeof(ulong));
103 shiftexp = (ulong*) TMP_ALLOC(N*sizeof(ulong));
104 mpoly_set_monomial_ui(shiftexp, Ashift, Abits, ctx->minfo);
105 mpoly_gen_monomial_sp(strideexp, var, Abits, ctx->minfo);
106 mpoly_monomial_mul_ui(strideexp, strideexp, N, Astride[var]);
107
108 fmpz_mod_mpoly_fit_length_reset_bits(A, 0, Abits, ctx);
109
110 Acoeff = A->coeffs;
111 Aexp = A->exps;
112 Alen = 0;
113 for (k = Bdeg; k >= 0; k--)
114 {
115 _fmpz_mod_mpoly_fit_length(&Acoeff, &A->coeffs_alloc,
116 &Aexp, &A->exps_alloc, N, Alen + 1);
117 fmpz_mod_poly_get_coeff_fmpz(Acoeff + Alen, B, k, ctx->ffinfo);
118 if (fmpz_is_zero(Acoeff + Alen))
119 continue;
120 mpoly_monomial_madd(Aexp + N*Alen, shiftexp, k, strideexp, N);
121 Alen++;
122 }
123
124 A->coeffs = Acoeff;
125 A->exps = Aexp;
126 _fmpz_mod_mpoly_set_length(A, Alen, ctx);
127
128 TMP_END;
129 }
130