void
nmod_poly_factor_cantor_zassenhaus(nmod_poly_factor_t res, const nmod_poly_t f)
{
nmod_poly_t h, v, g, x;
slong i, j, num;
nmod_poly_init_preinv(h, f->mod.n, f->mod.ninv);
nmod_poly_init_preinv(g, f->mod.n, f->mod.ninv);
nmod_poly_init_preinv(v, f->mod.n, f->mod.ninv);
nmod_poly_init_preinv(x, f->mod.n, f->mod.ninv);
nmod_poly_set_coeff_ui(h, 1, 1);
nmod_poly_set_coeff_ui(x, 1, 1);
nmod_poly_make_monic(v, f);
i = 0;
do
{
i++;
nmod_poly_powmod_ui_binexp(h, h, f->mod.n, v);
nmod_poly_sub(h, h, x);
nmod_poly_gcd(g, h, v);
nmod_poly_add(h, h, x);
if (g->length != 1)
{
nmod_poly_make_monic(g, g);
num = res->num;
nmod_poly_factor_equal_deg(res, g, i);
for (j = num; j < res->num; j++)
res->exp[j] = nmod_poly_remove(v, res->p + j);
}
}
while (v->length >= 2*i + 3);
if (v->length > 1)
nmod_poly_factor_insert(res, v, 1);
nmod_poly_clear(g);
nmod_poly_clear(h);
nmod_poly_clear(v);
nmod_poly_clear(x);
}
void
nmod_poly_factor_squarefree(nmod_poly_factor_t res, const nmod_poly_t f)
{
nmod_poly_t f_d, g, g_1;
mp_limb_t p;
slong deg, i;
if (f->length <= 1)
{
res->num = 0;
return;
}
if (f->length == 2)
{
nmod_poly_factor_insert(res, f, 1);
return;
}
p = nmod_poly_modulus(f);
deg = nmod_poly_degree(f);
/* Step 1, look at f', if it is zero then we are done since f = h(x)^p
for some particular h(x), clearly f(x) = sum a_k x^kp, k <= deg(f) */
nmod_poly_init(g_1, p);
nmod_poly_init(f_d, p);
nmod_poly_init(g, p);
nmod_poly_derivative(f_d, f);
/* Case 1 */
if (nmod_poly_is_zero(f_d))
{
nmod_poly_factor_t new_res;
nmod_poly_t h;
nmod_poly_init(h, p);
for (i = 0; i <= deg / p; i++) /* this will be an integer since f'=0 */
{
nmod_poly_set_coeff_ui(h, i, nmod_poly_get_coeff_ui(f, i * p));
}
/* Now run square-free on h, and return it to the pth power */
nmod_poly_factor_init(new_res);
nmod_poly_factor_squarefree(new_res, h);
nmod_poly_factor_pow(new_res, p);
nmod_poly_factor_concat(res, new_res);
nmod_poly_clear(h);
nmod_poly_factor_clear(new_res);
}
else
{
nmod_poly_t h, z;
nmod_poly_gcd(g, f, f_d);
nmod_poly_div(g_1, f, g);
i = 1;
nmod_poly_init(h, p);
nmod_poly_init(z, p);
/* Case 2 */
while (!nmod_poly_is_one(g_1))
{
nmod_poly_gcd(h, g_1, g);
nmod_poly_div(z, g_1, h);
/* out <- out.z */
if (z->length > 1)
{
nmod_poly_factor_insert(res, z, 1);
nmod_poly_make_monic(res->p + (res->num - 1),
res->p + (res->num - 1));
if (res->num)
res->exp[res->num - 1] *= i;
}
i++;
nmod_poly_set(g_1, h);
nmod_poly_div(g, g, h);
}
nmod_poly_clear(h);
nmod_poly_clear(z);
nmod_poly_make_monic(g, g);
if (!nmod_poly_is_one(g))
{
/* so now we multiply res with square-free(g^1/p) ^ p */
nmod_poly_t g_p; /* g^(1/p) */
nmod_poly_factor_t new_res_2;
nmod_poly_init(g_p, p);
for (i = 0; i <= nmod_poly_degree(g) / p; i++)
nmod_poly_set_coeff_ui(g_p, i, nmod_poly_get_coeff_ui(g, i*p));
nmod_poly_factor_init(new_res_2);
/* square-free(g^(1/p)) */
nmod_poly_factor_squarefree(new_res_2, g_p);
nmod_poly_factor_pow(new_res_2, p);
nmod_poly_factor_concat(res, new_res_2);
nmod_poly_clear(g_p);
nmod_poly_factor_clear(new_res_2);
}
}
nmod_poly_clear(g_1);
nmod_poly_clear(f_d);
nmod_poly_clear(g);
}
int
main(void)
{
int i, result;
flint_rand_t state;
printf("hensel_start_continue_lift....");
fflush(stdout);
flint_randinit(state);
/* We check that lifting local factors of F yields factors */
for (i = 0; i < 1000; i++)
{
fmpz_poly_t F, G, H, R;
nmod_poly_factor_t f_fac;
fmpz_poly_factor_t F_fac;
long bits, nbits, n, exp, j, part_exp;
long r;
fmpz_poly_t *v, *w;
long *link;
long prev_exp;
bits = n_randint(state, 200) + 1;
nbits = n_randint(state, FLINT_BITS - 6) + 6;
fmpz_poly_init(F);
fmpz_poly_init(G);
fmpz_poly_init(H);
fmpz_poly_init(R);
nmod_poly_factor_init(f_fac);
fmpz_poly_factor_init(F_fac);
n = n_randprime(state, nbits, 0);
exp = bits / (FLINT_BIT_COUNT(n) - 1) + 1;
part_exp = n_randint(state, exp);
/* Produce F as the product of random G and H */
{
nmod_poly_t f;
nmod_poly_init(f, n);
do {
do {
fmpz_poly_randtest(G, state, n_randint(state, 200) + 2, bits);
} while (G->length < 2);
fmpz_randtest_not_zero(G->coeffs, state, bits);
fmpz_one(fmpz_poly_lead(G));
do {
fmpz_poly_randtest(H, state, n_randint(state, 200) + 2, bits);
} while (H->length < 2);
fmpz_randtest_not_zero(H->coeffs, state, bits);
fmpz_one(fmpz_poly_lead(H));
fmpz_poly_mul(F, G, H);
fmpz_poly_get_nmod_poly(f, F);
} while (!nmod_poly_is_squarefree(f));
fmpz_poly_get_nmod_poly(f, G);
nmod_poly_factor_insert(f_fac, f, 1);
fmpz_poly_get_nmod_poly(f, H);
nmod_poly_factor_insert(f_fac, f, 1);
nmod_poly_clear(f);
}
r = f_fac->num;
v = flint_malloc((2*r - 2)*sizeof(fmpz_poly_t));
w = flint_malloc((2*r - 2)*sizeof(fmpz_poly_t));
link = flint_malloc((2*r - 2)*sizeof(long));
for (j = 0; j < 2*r - 2; j++)
{
fmpz_poly_init(v[j]);
fmpz_poly_init(w[j]);
}
if (part_exp < 1)
{
_fmpz_poly_hensel_start_lift(F_fac, link, v, w, F, f_fac, exp);
}
else
{
fmpz_t nn;
fmpz_init_set_ui(nn, n);
prev_exp = _fmpz_poly_hensel_start_lift(F_fac, link, v, w,
F, f_fac, part_exp);
_fmpz_poly_hensel_continue_lift(F_fac, link, v, w,
F, prev_exp, part_exp, exp, nn);
fmpz_clear(nn);
}
result = 1;
for (j = 0; j < F_fac->num; j++)
{
fmpz_poly_rem(R, F, F_fac->p + j);
result &= (R->length == 0);
}
for (j = 0; j < 2*r - 2; j++)
{
fmpz_poly_clear(v[j]);
fmpz_poly_clear(w[j]);
}
flint_free(link);
flint_free(v);
flint_free(w);
if (!result)
{
printf("FAIL:\n");
printf("bits = %ld, n = %ld, exp = %ld\n", bits, n, exp);
fmpz_poly_print(F); printf("\n\n");
fmpz_poly_print(G); printf("\n\n");
fmpz_poly_print(H); printf("\n\n");
fmpz_poly_factor_print(F_fac); printf("\n\n");
abort();
}
nmod_poly_factor_clear(f_fac);
fmpz_poly_factor_clear(F_fac);
fmpz_poly_clear(F);
fmpz_poly_clear(H);
fmpz_poly_clear(G);
fmpz_poly_clear(R);
}
flint_randclear(state);
_fmpz_cleanup();
printf("PASS\n");
return 0;
}
