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/*
Copyright (C) 2011 Fredrik Johansson
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "ulong_extras.h"
#include "fmpz.h"
#include "fmpz_mat.h"
#define E(j,k) fmpz_mat_entry(B,j,k)
#define r_shift(in, c) (((c) == FLINT_BITS) ? WORD(0) : ((in) >> (c)))
slong
fmpz_mat_fflu(fmpz_mat_t B, fmpz_t den, slong * perm,
const fmpz_mat_t A, int rank_check)
{
slong m, n, j, k, rank, r, pivot_row, pivot_col, norm = 0;
ulong p1h, p1l, p2h, p2l, uden = 0, dinv = 0, quo;
ulong FLINT_SET_BUT_UNUSED(rem);
slong mbits = fmpz_mat_max_bits(A);
int small = FLINT_ABS(mbits) <= SMALL_FMPZ_BITCOUNT_MAX;
int dsgn = 0, sgn, den1 = 0, work_to_do;
/* we set den in case matrix has no pivots */
fmpz_one(den);
if (fmpz_mat_is_empty(A))
return 0;
fmpz_mat_set(B, A);
m = B->r;
n = B->c;
rank = pivot_row = pivot_col = 0;
while (pivot_row < m && pivot_col < n)
{
r = fmpz_mat_find_pivot_any(B, pivot_row, m, pivot_col);
if (r == -1)
{
if (rank_check)
{
fmpz_zero(den);
rank = 0;
break;
}
pivot_col++;
continue;
}
else if (r != pivot_row)
fmpz_mat_swap_rows(B, perm, pivot_row, r);
rank++;
if (small)
{
for (j = pivot_row + 1; j < m; j++)
{
work_to_do = !den1 || !fmpz_is_zero(E(j, pivot_col)) ||
!fmpz_is_one(E(pivot_row, pivot_col));
if (work_to_do)
{
for (k = pivot_col + 1; k < n; k++)
{
smul_ppmm(p1h, p1l, *E(j, k), *E(pivot_row, pivot_col));
smul_ppmm(p2h, p2l, *E(j, pivot_col), *E(pivot_row, k));
sub_ddmmss(p1h, p1l, p1h, p1l, p2h, p2l);
sgn = 0 > (slong) p1h;
if (sgn) /* take absolute value */
sub_ddmmss(p1h, p1l, UWORD(0), UWORD(0), p1h, p1l);
if (pivot_row > 0 && !den1)
{
if (p1h >= uden)
{
fmpz_set_uiui(E(j, k), p1h, p1l);
if (sgn)
fmpz_neg(E(j, k), E(j, k));
fmpz_divexact(E(j, k), E(j, k), den);
small = 0;
} else
{
udiv_qrnnd_preinv(quo, rem,
(p1h << norm) +
r_shift(p1l, (FLINT_BITS - norm)),
p1l << norm, uden << norm, dinv);
if (sgn ^ dsgn)
fmpz_neg_ui(E(j, k), quo);
else
fmpz_set_ui(E(j, k), quo);
if (quo > COEFF_MAX)
small = 0;
}
} else
{
if (p1h > 0)
{
fmpz_set_uiui(E(j, k), p1h, p1l);
small = 0;
} else
{
fmpz_set_ui(E(j, k), p1l);
if (p1l > COEFF_MAX)
small = 0;
}
if (sgn)
fmpz_neg(E(j, k), E(j, k));
}
}
}
}
} else
{
for (j = pivot_row + 1; j < m; j++)
{
for (k = pivot_col + 1; k < n; k++)
{
fmpz_mul(E(j, k), E(j, k), E(pivot_row, pivot_col));
fmpz_submul(E(j, k), E(j, pivot_col), E(pivot_row, k));
if (pivot_row > 0 && !den1)
fmpz_divexact(E(j, k), E(j, k), den);
}
}
}
fmpz_set(den, E(pivot_row, pivot_col));
den1 = fmpz_is_one(den);
if (small)
{
uden = FLINT_ABS((slong)(*den));
dsgn = 0 > (slong)(*den);
norm = flint_clz(uden);
dinv = n_preinvert_limb_prenorm(uden << norm);
if (fmpz_sizeinbase(den, 2) > SMALL_FMPZ_BITCOUNT_MAX)
small = 0;
}
pivot_row++;
pivot_col++;
}
return rank;
}