/* //////////////////////////////////////////////////////////////////////////////////////
* implementation
*/
tb_float_t tb_powf(tb_float_t x, tb_float_t y)
{
#ifdef TB_CONFIG_LIBM_HAVE_POWF
return powf(x, y);
#else
return (tb_float_t)tb_pow(x, y);
#endif
}
/* //////////////////////////////////////////////////////////////////////////////////////
* main
*/
tb_int_t tb_demo_other_test_main(tb_int_t argc, tb_char_t** argv)
{
#if 0
// s = m/n = -lnp / (ln2 * ln2) = -log2(p) / ln2
// k = s * ln2 = -log2(p)
// p = (1 - e^(-k/s))^k
tb_double_t p = 0.0001;
tb_double_t k = -tb_log2(p);
tb_double_t s = k / (tb_log2(2) / tb_log2(2.718281828459045));
tb_double_t v = tb_pow((1 - tb_exp(-k/s)), k);
tb_trace_i("p: %lf, k: %lf, s: %lf, v: %lf", p, k, s, v);
// p = (1 - e^(-k/s))^k
// lnp = k * ln(1 - e^(-k/s))
// (lnp) / k = ln(1 - e^(-k/s))
// e^((lnp) / k) = 1 - e^(-k/s)
// e^(-k/s) = 1 - e^((lnp) / k) = 1 - (e^lnp)^(1/k) = 1 - p^(1/k)
// -k/s = ln(1 - p^(1/k))
// s = -k / ln(1 - p^(1/k))
// s ~= -k / (-p^(1/k) + 0.5p^(2/k))
//
// c = p^(1/k)
// s = -k / ln(1 - c))
// s ~= -k / (-c-0.5c^2) = 2k / (2c + c * c)
tb_double_t p2 = 0.0001;
tb_double_t k2 = 5;
// tb_double_t tt = 1.0 - tb_pow(p2, 1.0 / k2);
// tb_double_t s2 = -k2 * tb_log2(2.718281828459045) / tb_log2(tt);
// tb_double_t s2 = k2 / tb_pow(p2, 1.0 / k2);
tb_double_t c2 = tb_pow(p2, 1.0 / k2);
tb_double_t s2 = (k2 + k2) / (c2 + c2 + c2 * c2);
tb_double_t v2 = tb_pow((1 - tb_exp(-k2/s2)), k2);
tb_trace_i("p: %lf, k: %lf, s: %lf, v: %lf", p2, k2, s2, v2);
#endif
return 0;
}
