I'm not a c compiler expert, but have a look at double precision pi It may be the difference between computational precision and "%Lf" display precision. I started looking into it, when I questioned the way GLib defined pi as a constant. They defined it out to 50 decimal places, but any use of it in it's long double is limited to 15 decimal places. One of the c gurus in that thread said that c's precision is only gauranteed to 10 decimal places, but with IEEE standards, it's common to see 15. I see 15. Eventually, I found mpfr which lets you set how many digits of precision you want to use. If you can show me a simple c program that computes and displays values out to 50 decimal places, with normal c, I would be greatful. Everything I see truncates it (pi) to 3.(15 decimal places).
For example, in this code, the value of pi is correctly printed as a string on the first line of output, but the subsequent lines all have garbage after the 15th decimal place.
#include <gtk/gtk.h>
/* gcc o test test.c `pkgconfig cflags libs gtk+2.0` */
int main (){
/* how the headers define G_PI */
/* #define G_PI 3.1415926535897932384626433832795028841971693993751
+
*/
long double PI = G_PI;
g_print("3.1415926535897932384626433832795028841971693993751\n");
g_print("%0.50e\n",G_PI);
g_print("%0.50Lf\n",G_PI);
g_print("%0.50Lf\n",PI);
g_print("%0.50Lg\n",PI);
g_print("%0.50Le\n",PI);
return 0;
}
Output:
^^^^^^^^^^^ > unstable after 15 dec
+imal
3.1415926535897932384626433832795028841971693993751
3.14159265358979311599796346854418516159057617187500e+00
0.00000000000000000000000000000000000000000000000000
3.14159265358979311599796346854418516159057617187500
3.141592653589793115997963468544185161590576171875
3.14159265358979311599796346854418516159057617187500e+00
^^^^^^^^^^^^ > unstable after 15 dec
+imal
