static void arb_supremum(arf_t res, const arb_t x) { if (arf_is_nan(arb_midref(x))) { arf_nan(res); } else if (mag_is_inf(arb_radref(x))) { arf_pos_inf(res); } else { arf_set_mag(res, arb_radref(x)); arf_add(res, res, arb_midref(x), ARF_PREC_EXACT, ARF_RND_CEIL); } }
void arf_set_fmpr(arf_t y, const fmpr_t x) { if (fmpr_is_special(x)) { if (fmpr_is_zero(x)) arf_zero(y); else if (fmpr_is_pos_inf(x)) arf_pos_inf(y); else if (fmpr_is_neg_inf(x)) arf_neg_inf(y); else arf_nan(y); } else { arf_set_fmpz(y, fmpr_manref(x)); fmpz_add_inline(ARF_EXPREF(y), ARF_EXPREF(y), fmpr_expref(x)); } }
int arf_sum(arf_t s, arf_srcptr terms, long len, long prec, arf_rnd_t rnd) { arf_ptr blocks; long i, j, used; int have_merged, res; /* first check if the result is inf or nan */ { int have_pos_inf = 0; int have_neg_inf = 0; for (i = 0; i < len; i++) { if (arf_is_pos_inf(terms + i)) { if (have_neg_inf) { arf_nan(s); return 0; } have_pos_inf = 1; } else if (arf_is_neg_inf(terms + i)) { if (have_pos_inf) { arf_nan(s); return 0; } have_neg_inf = 1; } else if (arf_is_nan(terms + i)) { arf_nan(s); return 0; } } if (have_pos_inf) { arf_pos_inf(s); return 0; } if (have_neg_inf) { arf_neg_inf(s); return 0; } } blocks = flint_malloc(sizeof(arf_struct) * len); for (i = 0; i < len; i++) arf_init(blocks + i); /* put all terms into blocks */ used = 0; for (i = 0; i < len; i++) { if (!arf_is_zero(terms + i)) { arf_set(blocks + used, terms + i); used++; } } /* merge blocks until all are well separated */ have_merged = 1; while (used >= 2 && have_merged) { have_merged = 0; for (i = 0; i < used && !have_merged; i++) { for (j = i + 1; j < used && !have_merged; j++) { if (_arf_are_close(blocks + i, blocks + j, prec)) { arf_add(blocks + i, blocks + i, blocks + j, ARF_PREC_EXACT, ARF_RND_DOWN); /* remove the merged block */ arf_swap(blocks + j, blocks + used - 1); used--; /* remove the updated block if the sum is zero */ if (arf_is_zero(blocks + i)) { arf_swap(blocks + i, blocks + used - 1); used--; } have_merged = 1; } } } } if (used == 0) { arf_zero(s); res = 0; } else if (used == 1) { res = arf_set_round(s, blocks + 0, prec, rnd); } else { /* find the two largest blocks */ for (i = 1; i < used; i++) if (arf_cmpabs(blocks + 0, blocks + i) < 0) arf_swap(blocks + 0, blocks + i); for (i = 2; i < used; i++) if (arf_cmpabs(blocks + 1, blocks + i) < 0) arf_swap(blocks + 1, blocks + i); res = _arf_add_eps(s, blocks + 0, arf_sgn(blocks + 1), prec, rnd); } for (i = 0; i < len; i++) arf_clear(blocks + i); flint_free(blocks); return res; }
int acb_calc_integrate_taylor(acb_t res, acb_calc_func_t func, void * param, const acb_t a, const acb_t b, const arf_t inner_radius, const arf_t outer_radius, long accuracy_goal, long prec) { long num_steps, step, N, bp; int result; acb_t delta, m, x, y1, y2, sum; acb_ptr taylor_poly; arf_t err; acb_init(delta); acb_init(m); acb_init(x); acb_init(y1); acb_init(y2); acb_init(sum); arf_init(err); acb_sub(delta, b, a, prec); /* precision used for bounds calculations */ bp = MAG_BITS; /* compute the number of steps */ { arf_t t; arf_init(t); acb_get_abs_ubound_arf(t, delta, bp); arf_div(t, t, inner_radius, bp, ARF_RND_UP); arf_mul_2exp_si(t, t, -1); num_steps = (long) (arf_get_d(t, ARF_RND_UP) + 1.0); /* make sure it's not something absurd */ num_steps = FLINT_MIN(num_steps, 10 * prec); num_steps = FLINT_MAX(num_steps, 1); arf_clear(t); } result = ARB_CALC_SUCCESS; acb_zero(sum); for (step = 0; step < num_steps; step++) { /* midpoint of subinterval */ acb_mul_ui(m, delta, 2 * step + 1, prec); acb_div_ui(m, m, 2 * num_steps, prec); acb_add(m, m, a, prec); if (arb_calc_verbose) { printf("integration point %ld/%ld: ", 2 * step + 1, 2 * num_steps); acb_printd(m, 15); printf("\n"); } /* evaluate at +/- x */ /* TODO: exactify m, and include error in x? */ acb_div_ui(x, delta, 2 * num_steps, prec); /* compute bounds and number of terms to use */ { arb_t cbound, xbound, rbound; arf_t C, D, R, X, T; double DD, TT, NN; arb_init(cbound); arb_init(xbound); arb_init(rbound); arf_init(C); arf_init(D); arf_init(R); arf_init(X); arf_init(T); /* R is the outer radius */ arf_set(R, outer_radius); /* X = upper bound for |x| */ acb_get_abs_ubound_arf(X, x, bp); arb_set_arf(xbound, X); /* Compute C(m,R). Important subtlety: due to rounding when computing m, we will in general be farther than R away from the integration path. But since acb_calc_cauchy_bound actually integrates over the area traced by a complex interval, it will catch any extra singularities (giving an infinite bound). */ arb_set_arf(rbound, outer_radius); acb_calc_cauchy_bound(cbound, func, param, m, rbound, 8, bp); arf_set_mag(C, arb_radref(cbound)); arf_add(C, arb_midref(cbound), C, bp, ARF_RND_UP); /* Sanity check: we need C < inf and R > X */ if (arf_is_finite(C) && arf_cmp(R, X) > 0) { /* Compute upper bound for D = C * R * X / (R - X) */ arf_mul(D, C, R, bp, ARF_RND_UP); arf_mul(D, D, X, bp, ARF_RND_UP); arf_sub(T, R, X, bp, ARF_RND_DOWN); arf_div(D, D, T, bp, ARF_RND_UP); /* Compute upper bound for T = (X / R) */ arf_div(T, X, R, bp, ARF_RND_UP); /* Choose N */ /* TODO: use arf arithmetic to avoid overflow */ /* TODO: use relative accuracy (look at |f(m)|?) */ DD = arf_get_d(D, ARF_RND_UP); TT = arf_get_d(T, ARF_RND_UP); NN = -(accuracy_goal * 0.69314718055994530942 + log(DD)) / log(TT); N = NN + 0.5; N = FLINT_MIN(N, 100 * prec); N = FLINT_MAX(N, 1); /* Tail bound: D / (N + 1) * T^N */ { mag_t TT; mag_init(TT); arf_get_mag(TT, T); mag_pow_ui(TT, TT, N); arf_set_mag(T, TT); mag_clear(TT); } arf_mul(D, D, T, bp, ARF_RND_UP); arf_div_ui(err, D, N + 1, bp, ARF_RND_UP); } else { N = 1; arf_pos_inf(err); result = ARB_CALC_NO_CONVERGENCE; } if (arb_calc_verbose) { printf("N = %ld; bound: ", N); arf_printd(err, 15); printf("\n"); printf("R: "); arf_printd(R, 15); printf("\n"); printf("C: "); arf_printd(C, 15); printf("\n"); printf("X: "); arf_printd(X, 15); printf("\n"); } arb_clear(cbound); arb_clear(xbound); arb_clear(rbound); arf_clear(C); arf_clear(D); arf_clear(R); arf_clear(X); arf_clear(T); } /* evaluate Taylor polynomial */ taylor_poly = _acb_vec_init(N + 1); func(taylor_poly, m, param, N, prec); _acb_poly_integral(taylor_poly, taylor_poly, N + 1, prec); _acb_poly_evaluate(y2, taylor_poly, N + 1, x, prec); acb_neg(x, x); _acb_poly_evaluate(y1, taylor_poly, N + 1, x, prec); acb_neg(x, x); /* add truncation error */ arb_add_error_arf(acb_realref(y1), err); arb_add_error_arf(acb_imagref(y1), err); arb_add_error_arf(acb_realref(y2), err); arb_add_error_arf(acb_imagref(y2), err); acb_add(sum, sum, y2, prec); acb_sub(sum, sum, y1, prec); if (arb_calc_verbose) { printf("values: "); acb_printd(y1, 15); printf(" "); acb_printd(y2, 15); printf("\n"); } _acb_vec_clear(taylor_poly, N + 1); if (result == ARB_CALC_NO_CONVERGENCE) break; } acb_set(res, sum); acb_clear(delta); acb_clear(m); acb_clear(x); acb_clear(y1); acb_clear(y2); acb_clear(sum); arf_clear(err); return result; }