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Directly discard conjugates in complex case.

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This commit is contained in:
Jean-Pierre Flori 2018-01-18 16:22:03 +01:00
parent 16f5dcec29
commit c0983585c0
1 changed files with 4 additions and 18 deletions
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22
arb_fmpz_poly/gauss_period_minpoly.c
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@ -19,7 +19,6 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
ulong * es;
slong prec, initial_prec;
int done, real;
int * lower_plane;
if (n == 0 || !n_is_prime(q) || ((q - 1) % n) != 0 ||
n_gcd_full(n, (q - 1) / n) != 1)
@ -41,7 +40,6 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
qinv = n_preinvert_limb(q);
es = flint_malloc(sizeof(ulong) * d);
lower_plane = flint_calloc(n, sizeof(int));
for (e = 0; e < d; e++)
es[e] = n_powmod2(g, n * e, q);
@ -64,7 +62,6 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
arb_ptr roots;
acb_ptr croots;
acb_t t, u;
slong root_index;
acb_dirichlet_roots_init(zeta, q, n * d, prec);
roots = _arb_vec_init(n);
@ -74,13 +71,8 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
acb_init(u);
arb_poly_init(pz);
root_index = 0;
for (k = 0; k < n; k++)
for (k = 0; k < (real ? n : n / 2); k++)
{
if (lower_plane[k])
continue;
gk = n_powmod2(g, k, q);
acb_zero(u);
@ -103,11 +95,7 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
acb_add(u, u, t, prec);
}
if (arb_is_negative(acb_imagref(u)))
{
lower_plane[k] = 1;
}
else if (arb_contains_zero(acb_imagref(u)))
if (arb_contains_zero(acb_imagref(u)))
{
/* todo: could increase precision */
flint_printf("fail! imaginary part should be nonzero\n");
@ -115,8 +103,7 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
}
else
{
acb_set(croots + root_index, u);
root_index++;
acb_set(croots + k, u);
}
}
}
@ -124,7 +111,7 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
if (real)
arb_poly_product_roots(pz, roots, n, prec);
else
arb_poly_product_roots_complex(pz, NULL, 0, croots, root_index, prec);
arb_poly_product_roots_complex(pz, NULL, 0, croots, n / 2, prec);
done = arb_poly_get_unique_fmpz_poly(res, pz);
@ -161,6 +148,5 @@ arb_fmpz_poly_gauss_period_minpoly(fmpz_poly_t res, ulong q, ulong n)
}
flint_free(es);
flint_free(lower_plane);
}