void
_qseive(const mp_limb_t n, const mp_limb_t B)
{
nmod_sparse_mat_t M;
mp_limb_t quad, *quads, *xs, x, i = 0, j, piB = n_prime_pi(B);
const mp_limb_t * ps = n_primes_arr_readonly(piB + 2);
const double * pinvs = n_prime_inverses_arr_readonly(piB + 2);
mzd_t *K;
/* init */
quads = (mp_limb_t *)malloc((piB + 1)*sizeof(mp_limb_t *));
xs = (mp_limb_t *)malloc((piB + 1)*sizeof(mp_limb_t *));
K = mzd_init(piB + 1, 1);
nmod_sparse_mat_init(M, piB + 1, piB + 1, 2);
printf("init done\n");
printf("using %ld primes\n", piB);
/* seive */
for (x = n_sqrt(n), i = 0; i <= piB; x++)
{
quad = x*x - n;
if (quad == 0)
continue;
for (j = 0; j < piB; j++)
n_remove2_precomp(&quad, ps[j], pinvs[j]);
if (quad == 1) /* was B-smooth */
{
quads[i] = x*x - n;
quad = x*x - n;
for (j = 0; j < piB; j++)
{
if (n_remove2_precomp(&quad, ps[j], pinvs[j]) % 2)
_nmod_sparse_mat_set_entry(M, j, i, M->row_supports[j], 1);
}
xs[i] = x;
i++;
}
}
printf("data collection done\n");
n_cleanup_primes();
_bw(K, M, 1, 2, 7, 7);
printf("procesing complete\n");
mzd_print(K);
int done = 0;
for (j = 0; !done; j++)
{
fmpz_t a, b, diff, N;
fmpz_init_set_ui(a, 1);
fmpz_init_set_ui(b, 1);
fmpz_init_set_ui(N, n);
fmpz_init(diff);
for (i = 0; i < piB; i++)
{
if (mzd_read_bit(K, i, j))
{
fmpz_mul_ui(a, a, xs[i]);
fmpz_mul_ui(b, b, quads[i]);
}
}
assert(fmpz_is_square(b));
fmpz_sqrt(b, b);
if (fmpz_mod_ui(a, a, n) != fmpz_mod_ui(b, b, n) && fmpz_mod_ui(a, a, n) != n - fmpz_mod_ui(b, b, n))
{
done = 1;
fmpz_print(a);
printf("\n");
fmpz_print(b);
printf("\n");
fmpz_sub(diff, a, b);
fmpz_gcd(a, diff, N);
fmpz_divexact(b, N, a);
fmpz_print(a);
printf("\n");
fmpz_print(b);
}
fmpz_clear(a);
fmpz_clear(b);
fmpz_clear(N);
fmpz_clear(diff);
}
/* cleanup */
free(quads);
free(xs);
mzd_free(K);
nmod_sparse_mat_clear(M);
return;
}
int
_fmpz_poly_sqrt_classical(fmpz * res, const fmpz * poly, long len)
{
long i, m;
int result;
/* the degree must be even */
if (len % 2 == 0)
return 0;
/* valuation must be even, and then can be reduced to 0 */
while (fmpz_is_zero(poly))
{
if (!fmpz_is_zero(poly + 1))
return 0;
fmpz_zero(res);
poly += 2;
len -= 2;
res++;
}
/* check whether a square root exists modulo 2 */
for (i = 1; i < len; i += 2)
if (!fmpz_is_even(poly + i))
return 0;
/* check endpoints */
if (!fmpz_is_square(poly) || (len > 1 && !fmpz_is_square(poly + len - 1)))
return 0;
/* square root of leading coefficient */
m = (len + 1) / 2;
fmpz_sqrt(res + m - 1, poly + len - 1);
result = 1;
/* do long divison style 'square root with remainder' from top to bottom */
if (len > 1)
{
fmpz_t t, u;
fmpz * r;
fmpz_init(t);
fmpz_init(u);
r = _fmpz_vec_init(len);
_fmpz_vec_set(r, poly, len);
fmpz_mul_ui(u, res + m - 1, 2);
for (i = 1; i < m; i++)
{
fmpz_fdiv_qr(res + m - i - 1, t, r + len - i - 1, u);
if (!fmpz_is_zero(t))
{
result = 0;
break;
}
fmpz_mul_si(t, res + m - i - 1, -2);
_fmpz_vec_scalar_addmul_fmpz(r + len - 2*i, res + m - i, i - 1, t);
fmpz_submul(r + len - 2*i - 1, res + m - i - 1, res + m - i - 1);
}
for (i = m; i < len && result; i++)
if (!fmpz_is_zero(r + len - 1 - i))
result = 0;
_fmpz_vec_clear(r, len);
fmpz_clear(t);
fmpz_clear(u);
}
return result;
}
