Nick Ing-Simmons <[EMAIL PROTECTED]> writes:
> Dan Sugalski <[EMAIL PROTECTED]> writes:
> >At 10:55 AM 8/2/00 +0200, Gisle Aas wrote:
> >>All functions that return time values (seconds since epoch) should use
> >>floating point numbers to return as much precision as the platform
> >>supports. All functions that take time values as arguments should
> >>work for fractional seconds if the platform supports it.
> >
> >Floats have resolution issues that exacerbate sub-second resolution issues.
>
> As an engineer I would really like to know when you are going to
> run out of precision in double - that is forty something bits of mantissa.
> That is more precision than you have in the real world.
If I measure the duration of something with code like this:
my $before = time;
do_something();
my $duration = time - $before;
print "$duration";
Then the use of double will limit the precision to something like 1e-6
sec. I'm not sure that this is enough for the future, but I don't
really know. What is the precision of the real world?
I used this simple script to experiment with double time precision:
$prec = shift || 6;
die if $prec < 2;
my $t = int(time) . "." . ("0" x ($prec - 2));
my $t1 = $t . "34";
my $t2 = $t . "35";
printf "$t2 - $t1 = %.4e\n", $t2 - $t1;
Perhaps this only measure how precise strtod() is?
--Gisle
