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/* This file is public domain. Author: Fredrik Johansson. */
#include <stdlib.h>
#include <flint/arb.h>
#include <flint/profiler.h>
int main(int argc, char *argv[])
{
slong prec, goal, digits;
const char * xs;
const char * rs;
arb_t x, r, s, t;
slong i, n;
if (argc < 2)
{
flint_printf("nth iterate of the logistic map x_{n+1} = r x_n (1-x_n)\n");
flint_printf("usage: build/examples/logistic n [x_0=0.5] [r=3.75] [digits=10]\n");
return 1;
}
n = atol(argv[1]);
n = FLINT_MAX(n, 0);
xs = (argc >= 3) ? argv[2] : "0.5";
rs = (argc >= 4) ? argv[3] : "3.75";
digits = (argc >= 5) ? atol(argv[4]) : 10;
if (digits < 1)
digits = 1;
goal = digits * 3.3219280948873623 + 3;
arb_init(x);
arb_init(r);
arb_init(s);
arb_init(t);
TIMEIT_ONCE_START;
for (prec = 64; ; prec *= 2)
{
flint_printf("Trying prec=%wd bits...", prec);
fflush(stdout);
arb_set_str(x, xs, prec);
arb_set_str(r, rs, prec);
if (!arb_is_finite(x) || !arb_is_finite(r))
{
flint_printf("unable to parse input string!\n");
flint_abort();
}
for (i = 0; i < n; i++)
{
arb_sub_ui(t, x, 1, prec);
arb_neg(t, t);
arb_mul(x, x, t, prec);
arb_mul(x, x, r, prec);
if (arb_rel_accuracy_bits(x) < goal)
{
flint_printf("ran out of accuracy at step %wd\n", i);
break;
}
}
if (i == n)
{
flint_printf("success!\n");
break;
}
}
TIMEIT_ONCE_STOP;
flint_printf("x_%wd = ", n);
arb_printn(x, digits, 0);
flint_printf("\n");
arb_clear(x);
arb_clear(r);
arb_clear(s);
arb_clear(t);
flint_cleanup();
return 0;
}
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