On Tue, 9 Nov 2010, [email protected] wrote: > Ian Smith <[email protected]> wrote: > > In freebsd-questions Digest, Vol 335, Issue 11, Message: 4 > > On Sat, 06 Nov 2010 01:00:34 -0700 [email protected] wrote: > > > Julian Fagir <[email protected]> wrote: > > > > > Does anyone has a "generate-pi.c" source code? > > > ... > > > > 1 #include <stdlib.h> > > > > 2 #include <string.h> > > > > 3 #include <stdio.h> > > > > 4 > > > > 5 // Change this for a more accurate result. > > > > 6 long max = 100000000; > > > > 7 double a, b; > > > > 8 double pi; > > > > 9 long counter; > > > > 10 long i; > > > > 11 > > > > 12 int main() { > > > > 13 for (i = 0; i< max; i++) { > > > > 14 a = drand48(); > > > > 15 b = drand48(); > > > > 16 if (a*a + b*b <= 1) > > > > 17 counter++; > > > > 18 } > > > > 19 pi = 4*counter; > > > > Surely that should be 'pi = 4 * counter / max;' otherwise even if the > > integer counter were only 1 (of 100000000), pi would already be 4 :) > > The part I snipped out included a note that it was only generating > the digits, not trying to show the decimal point placed properly.
Ah. > With that understanding, and as long as max is a (large-ish) power > of 10, the division is not needed. (If the division were to be > inserted, at least one of its operands would need to be cast to > double, or pi would likely be reported as 3.0000 due to truncation.) Ok, you can probably tell that I'm not really proficient in C; as an old Pascal programmer I'd have assumed an implied cast to pi's type, though I'd likely have specified 4.0 to make it clear. > An approach more in keeping with the original would involve using > sprintf, and then inserting the decimal point into the resulting > string :) It's a bit O(N) to use for many digits .. still I like the approach. cheers, Ian _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[email protected]"
