void fmpq_poly_revert_series_lagrange_fast(fmpq_poly_t res, const fmpq_poly_t poly, slong n) { fmpz *copy; int alloc; if (poly->length < 2 || !fmpz_is_zero(poly->coeffs) || fmpz_is_zero(poly->coeffs + 1)) { flint_printf("Exception (fmpq_poly_revert_series_lagrange_fast). Input must \n" "have zero constant term and nonzero coefficient of x^1.\n"); abort(); } if (n < 2) { fmpq_poly_zero(res); return; } if (poly->length >= n) { copy = poly->coeffs; alloc = 0; } else { slong i; copy = (fmpz *) flint_malloc(n * sizeof(fmpz)); for (i = 0; i < poly->length; i++) copy[i] = poly->coeffs[i]; for ( ; i < n; i++) copy[i] = 0; alloc = 1; } if (res != poly) { fmpq_poly_fit_length(res, n); _fmpq_poly_revert_series_lagrange_fast(res->coeffs, res->den, copy, poly->den, n); } else { fmpq_poly_t t; fmpq_poly_init2(t, n); _fmpq_poly_revert_series_lagrange_fast(t->coeffs, t->den, copy, poly->den, n); fmpq_poly_swap(res, t); fmpq_poly_clear(t); } _fmpq_poly_set_length(res, n); _fmpq_poly_normalise(res); if (alloc) flint_free(copy); }
void _fmpq_poly_revert_series(fmpz * Qinv, fmpz_t den, const fmpz * Q, const fmpz_t Qden, long n) { _fmpq_poly_revert_series_lagrange_fast(Qinv, den, Q, Qden, n); }