On Wed, Sep 24, 2014 at 10:49 AM, RSmith <[email protected]> wrote:
> I'm trying to find what the limit is for dividing in terms of accuracy.
>
> Basically I have one program that inserts values to a table and determine
> sort order using one standard trick that has a REAL column named
> "SortOrder" which gets the value Highest_previous_value+1 if an insert
> happens with something that needs to be sorted at the end of the table.
>
> For any other position, the SortOrder gets assigned the value:
> ((Prev.Sortorder + Next.Sortorder) / 2)
>
{snipped}
A quick bit of test code shows me that after 53 iterations you'll run out
of precision, which makes sense because there are 53 mantissa bits in a
normalized double including the implicit leading 1 bit).
My quick & dirty test code which may be useful.
#include <stdio.h>
int main()
{
double lo = 1.0;
double hi = 2.0;
int count = 0;
while (lo != hi)
{
double mid = (lo + hi) / 2.0;
printf("%d %f\n", ++count, mid);
lo = mid;
}
return 0;
}
--
Scott Robison
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