Possible issue and solution for RoundNanoFraction functions
Posted: 31.01.2024, 14:12
I ran into an issue with the rounding of nano timestamps a while ago. The suspect code is in ZSysUtils. My test case is:
x := RoundNanoFractionTo(123456789, 3);
and
x := RoundNanoFractionToMillis(123456789);
and I think x should be 123000000 but the actual result is 124000000.
This tracks back to:
const HalfFractModulos: array [TFractionRoundToScale] of Cardinal = ( 444444445, 44444445, 4444445, 444445, 44445, 4445, 445, 45, 5,0);
and to get it to give the results I'd expect I changed it to:
const HalfFractModulos: array [TFractionRoundToScale] of Cardinal = ( 500000000, 50000000, 5000000, 500000, 50000, 5000, 500, 50, 5,0);
Can someone check my logic here? Thanks!
-Mark
x := RoundNanoFractionTo(123456789, 3);
and
x := RoundNanoFractionToMillis(123456789);
and I think x should be 123000000 but the actual result is 124000000.
This tracks back to:
const HalfFractModulos: array [TFractionRoundToScale] of Cardinal = ( 444444445, 44444445, 4444445, 444445, 44445, 4445, 445, 45, 5,0);
and to get it to give the results I'd expect I changed it to:
const HalfFractModulos: array [TFractionRoundToScale] of Cardinal = ( 500000000, 50000000, 5000000, 500000, 50000, 5000, 500, 50, 5,0);
Can someone check my logic here? Thanks!
-Mark
