int fmpq_poly_oz_sqrt_approx_pade(fmpq_poly_t f_sqrt, const fmpq_poly_t f, const long n, const int p, const mpfr_prec_t prec, const mpfr_prec_t bound, oz_flag_t flags, const fmpq_poly_t init) {
fmpq_poly_t y; fmpq_poly_init(y);
fmpq_poly_t y_next; fmpq_poly_init(y_next);
fmpq_poly_t z; fmpq_poly_init(z);
fmpq_poly_t z_next; fmpq_poly_init(z_next);
mpfr_t norm; mpfr_init2(norm, prec);
mpfr_t prev_norm; mpfr_init2(prev_norm, prec);
mpfr_t log_f; mpfr_init2(log_f, prec);
if (init) {
// z = y/x
fmpq_poly_set(y, init);
_fmpq_poly_oz_invert_approx(z, f, n, prec);
fmpq_poly_oz_mul(z, z, y, n);
} else {
fmpq_poly_set(y, f);
fmpq_poly_set_coeff_si(z, 0, 1);
}
fmpq_t *xi = (fmpq_t*)calloc(p, sizeof(fmpq_t));
fmpq_t *a2 = (fmpq_t*)calloc(p, sizeof(fmpq_t));
fmpq_t *c = (fmpq_t*)calloc(p, sizeof(fmpq_t));
fmpq_poly_t *t_ = (fmpq_poly_t*)calloc(p, sizeof(fmpq_poly_t));
fmpq_poly_t *s_ = (fmpq_poly_t*)calloc(p, sizeof(fmpq_poly_t));
mpfr_t pi; mpfr_init2(pi, 4*prec);
mpfr_const_pi(pi, MPFR_RNDN);
#pragma omp parallel for
for(int i=0; i<p; i++) {
mpfr_t xi_r; mpfr_init2(xi_r, 4*prec);
mpfr_t a2_r; mpfr_init2(a2_r, 4*prec);
/* ζ_i = 1/2 * (1 + cos( (2·i -1)·π/(2·p) )) */
mpfr_set_si(xi_r, 2*i+1, MPFR_RNDN);
mpfr_mul(xi_r, xi_r, pi, MPFR_RNDN);
mpfr_div_si(xi_r, xi_r, 2*p, MPFR_RNDN);
mpfr_cos(xi_r, xi_r, MPFR_RNDN);
mpfr_add_si(xi_r, xi_r, 1, MPFR_RNDN);
mpfr_div_si(xi_r, xi_r, 2, MPFR_RNDN);
/* α_i^2 = 1/ζ_i -1 */
mpfr_set_si(a2_r, 1, MPFR_RNDN);
mpfr_div(a2_r, a2_r, xi_r, MPFR_RNDN);
mpfr_sub_si(a2_r, a2_r, 1, MPFR_RNDN);
fmpq_init(xi[i]);
fmpq_init(a2[i]);
fmpq_set_mpfr(xi[i], xi_r, MPFR_RNDN);
fmpq_set_mpfr(a2[i], a2_r, MPFR_RNDN);
fmpq_init(c[i]);
fmpq_poly_init(t_[i]);
fmpq_poly_init(s_[i]);
mpfr_clear(xi_r);
mpfr_clear(a2_r);
}
mpfr_clear(pi);
uint64_t t = oz_walltime(0);
int r = 0;
int cont = 1;
for(long k=0; cont; k++) {
if (k == 0 || mpfr_cmp_ui(prev_norm, 1) > 0)
_fmpq_poly_oz_sqrt_approx_scale(y, z, n, prec);
/* T = sum([1/xi[i] * ~(Z*Y + a2[i]) for i in range(p)]) */
#pragma omp parallel for
for(int i=0; i<p; i++) {
fmpq_poly_oz_mul(t_[i], z, y, n);
fmpq_poly_get_coeff_fmpq(c[i], t_[i], 0);
fmpq_add(c[i], c[i], a2[i]);
fmpq_poly_set_coeff_fmpq(t_[i], 0, c[i]);
fmpq_poly_scalar_mul_fmpq(t_[i], t_[i], xi[i]);
_fmpq_poly_oz_invert_approx(s_[i], t_[i], n, prec);
}
for(int i=1; i<p; i++)
fmpq_poly_add(s_[0], s_[0], s_[i]);
#pragma omp parallel sections
{
#pragma omp section
{
fmpq_poly_oz_mul(y_next, y, s_[0], n);
fmpq_poly_scalar_div_si(y_next, y_next, p);
fmpq_poly_set(y, y_next);
}
#pragma omp section
{
fmpq_poly_oz_mul(z_next, z, s_[0], n);
fmpq_poly_scalar_div_si(z_next, z_next, p);
fmpq_poly_set(z, z_next);
}
}
cont = !_fmpq_poly_oz_sqrt_approx_break(norm, y, f, n, bound, prec);
if(flags & OZ_VERBOSE) {
mpfr_log2(log_f, norm, MPFR_RNDN);
mpfr_fprintf(stderr, "Computing sqrt(Σ):: k: %4d, Δ=|sqrt(Σ)^2-Σ|: %7.2Rf", k, log_f);
fprintf(stderr, " <? %4ld, ", -bound);
fprintf(stderr, "t: %8.2fs\n", oz_seconds(oz_walltime(t)));
fflush(0);
}
if (cont) {
if (k>0 && mpfr_cmp_ui_2exp(norm, 1, bound) >= 0) {
/* something went really wrong */
r = -1;
break;
}
if (k>0 && mpfr_cmp(norm, prev_norm) >= 0) {
/* we don't converge any more */
r = 1;
break;
}
mpfr_set(prev_norm, norm, MPFR_RNDN);
}
}
for(int i=0; i<p; i++) {
fmpq_clear(xi[i]);
fmpq_clear(a2[i]);
fmpq_clear(c[i]);
fmpq_poly_clear(t_[i]);
fmpq_poly_clear(s_[i]);
}
free(xi);
free(a2);
free(c);
free(t_);
free(s_);
mpfr_clear(log_f);
fmpq_poly_set(f_sqrt, y);
mpfr_clear(norm);
mpfr_clear(prev_norm);
fmpq_poly_clear(y_next);
fmpq_poly_clear(y);
fmpq_poly_clear(z_next);
fmpq_poly_clear(z);
return r;
}
int fmpq_poly_oz_sqrt_approx_babylonian(fmpq_poly_t f_sqrt, const fmpq_poly_t f, const long n, const mpfr_prec_t prec, const mpfr_prec_t bound, oz_flag_t flags, const fmpq_poly_t init) {
fmpq_poly_t y; fmpq_poly_init(y);
fmpq_poly_t y_next; fmpq_poly_init(y_next);
mpfr_t norm; mpfr_init2(norm, prec);
mpfr_t prev_norm; mpfr_init2(prev_norm, prec);
if (init) {
fmpq_poly_set(y, init);
} else {
fmpq_poly_set(y, f);
}
mpfr_t log_f;
mpfr_init2(log_f, prec);
uint64_t t = oz_walltime(0);
int r = 0;
for(long k=0; ; k++) {
_fmpq_poly_oz_invert_approx(y_next, y, n, prec);
fmpq_poly_oz_mul(y_next, f, y_next, n);
fmpq_poly_add(y_next, y_next, y);
fmpq_poly_scalar_div_si(y_next, y_next, 2);
fmpq_poly_set(y, y_next);
r = _fmpq_poly_oz_sqrt_approx_break(norm, y, f, n, bound, prec);
if(flags & OZ_VERBOSE) {
mpfr_log2(log_f, norm, MPFR_RNDN);
mpfr_fprintf(stderr, "Computing sqrt(Σ):: k: %4d, Δ=|sqrt(Σ)^2-Σ|: %7.2Rf", k, log_f);
fprintf(stderr, " <? %4ld, ", -bound);
fprintf(stderr, "t: %8.2fs\n", oz_seconds(oz_walltime(t)));
fflush(0);
}
if(r) {
r = 0;
break;
}
if (k>0 && mpfr_cmp_ui_2exp(norm, 1, bound) >= 0) {
/* something went really wrong */
r = -1;
break;
}
mpfr_div_ui(prev_norm, prev_norm, 2, MPFR_RNDN);
if (k>0 && mpfr_cmp(norm, prev_norm) >= 0) {
/* we don't converge any more */
r = 1;
break;
}
mpfr_set(prev_norm, norm, MPFR_RNDN);
}
mpfr_clear(log_f);
fmpq_poly_set(f_sqrt, y);
mpfr_clear(norm);
mpfr_clear(prev_norm);
fmpq_poly_clear(y_next);
fmpq_poly_clear(y);
return r;
}
int
main(void)
{
int i, result;
ulong cflags = UWORD(0);
FLINT_TEST_INIT(state);
flint_printf("scalar_div_fmpz....");
fflush(stdout);
/* Check aliasing of a and b */
for (i = 0; i < 1000 * flint_test_multiplier(); i++)
{
fmpq_poly_t a, b;
fmpz_t n;
fmpz_init(n);
fmpz_randtest_not_zero(n, state, 200);
fmpq_poly_init(a);
fmpq_poly_init(b);
fmpq_poly_randtest(a, state, n_randint(state, 100), 200);
fmpq_poly_scalar_div_fmpz(b, a, n);
fmpq_poly_scalar_div_fmpz(a, a, n);
cflags |= fmpq_poly_is_canonical(a) ? 0 : 1;
cflags |= fmpq_poly_is_canonical(b) ? 0 : 2;
result = (fmpq_poly_equal(a, b) && !cflags);
if (!result)
{
flint_printf("FAIL (aliasing):\n");
fmpq_poly_debug(a), flint_printf("\n\n");
fmpq_poly_debug(b), flint_printf("\n\n");
flint_printf("cflags = %wu\n\n", cflags);
fmpz_print(n);
abort();
}
fmpz_clear(n);
fmpq_poly_clear(a);
fmpq_poly_clear(b);
}
/* Compare with fmpq_poly_scalar_mul_si */
for (i = 0; i < 1000 * flint_test_multiplier(); i++)
{
fmpq_poly_t a, b, c;
fmpz_t n1;
slong n;
n = z_randtest_not_zero(state);
fmpz_init(n1);
fmpz_set_si(n1, n);
fmpq_poly_init(a);
fmpq_poly_init(b);
fmpq_poly_init(c);
fmpq_poly_randtest(a, state, n_randint(state, 100), 200);
fmpq_poly_scalar_div_fmpz(b, a, n1);
fmpq_poly_scalar_div_si(c, a, n);
cflags |= fmpq_poly_is_canonical(b) ? 0 : 1;
cflags |= fmpq_poly_is_canonical(c) ? 0 : 2;
result = (fmpq_poly_equal(b, c) && !cflags);
if (!result)
{
flint_printf("FAIL (comparison with _si):\n");
fmpq_poly_debug(a), flint_printf("\n\n");
fmpz_print(n1), flint_printf("\n\n");
fmpq_poly_debug(b), flint_printf("\n\n");
fmpq_poly_debug(c), flint_printf("\n\n");
flint_printf("cflags = %wu\n\n", cflags);
abort();
}
fmpz_clear(n1);
fmpq_poly_clear(a);
fmpq_poly_clear(b);
fmpq_poly_clear(c);
}
/* Check that (a / n1) / n2 == a / (n1 * n2) */
for (i = 0; i < 1000 * flint_test_multiplier(); i++)
{
fmpq_poly_t a, lhs, rhs;
fmpz_t n1, n2, n;
fmpz_init(n1);
fmpz_init(n2);
fmpz_init(n);
fmpz_randtest_not_zero(n1, state, 100);
fmpz_randtest_not_zero(n2, state, 100);
fmpz_mul(n, n1, n2);
fmpq_poly_init(a);
fmpq_poly_init(lhs);
fmpq_poly_init(rhs);
fmpq_poly_randtest(a, state, n_randint(state, 100), 200);
fmpq_poly_scalar_div_fmpz(lhs, a, n1);
fmpq_poly_scalar_div_fmpz(lhs, lhs, n2);
fmpq_poly_scalar_div_fmpz(rhs, a, n);
cflags |= fmpq_poly_is_canonical(lhs) ? 0 : 1;
cflags |= fmpq_poly_is_canonical(rhs) ? 0 : 2;
result = (fmpq_poly_equal(lhs, rhs) && !cflags);
if (!result)
{
flint_printf("FAIL (a / n1 / n2):\n");
fmpq_poly_debug(a), flint_printf("\n\n");
fmpz_print(n1), flint_printf("\n\n");
fmpz_print(n2), flint_printf("\n\n");
fmpz_print(n), flint_printf("\n\n");
fmpq_poly_debug(lhs), flint_printf("\n\n");
fmpq_poly_debug(rhs), flint_printf("\n\n");
flint_printf("cflags = %wu\n\n", cflags);
abort();
}
fmpz_clear(n1);
fmpz_clear(n2);
fmpz_clear(n);
fmpq_poly_clear(a);
fmpq_poly_clear(lhs);
fmpq_poly_clear(rhs);
}
/* Check that (a + b) / n == a/n + b/n */
for (i = 0; i < 1000 * flint_test_multiplier(); i++)
{
fmpq_poly_t a, b, lhs, rhs;
fmpz_t n;
fmpz_init(n);
fmpz_randtest_not_zero(n, state, 100);
fmpq_poly_init(a);
fmpq_poly_init(b);
fmpq_poly_init(lhs);
fmpq_poly_init(rhs);
fmpq_poly_randtest(a, state, n_randint(state, 100), 200);
fmpq_poly_randtest(b, state, n_randint(state, 100), 200);
fmpq_poly_scalar_div_fmpz(lhs, a, n);
fmpq_poly_scalar_div_fmpz(rhs, b, n);
fmpq_poly_add(rhs, lhs, rhs);
fmpq_poly_add(lhs, a, b);
fmpq_poly_scalar_div_fmpz(lhs, lhs, n);
cflags |= fmpq_poly_is_canonical(lhs) ? 0 : 1;
cflags |= fmpq_poly_is_canonical(rhs) ? 0 : 2;
result = (fmpq_poly_equal(lhs, rhs) && !cflags);
if (!result)
{
flint_printf("FAIL ((a + b) / n):\n");
fmpq_poly_debug(a), flint_printf("\n\n");
fmpq_poly_debug(b), flint_printf("\n\n");
fmpz_print(n), flint_printf("\n\n");
fmpq_poly_debug(lhs), flint_printf("\n\n");
fmpq_poly_debug(rhs), flint_printf("\n\n");
flint_printf("cflags = %wu\n\n", cflags);
abort();
}
fmpz_clear(n);
fmpq_poly_clear(a);
fmpq_poly_clear(b);
fmpq_poly_clear(lhs);
fmpq_poly_clear(rhs);
}
FLINT_TEST_CLEANUP(state);
flint_printf("PASS\n");
return 0;
}
