topic Rounding differences between QV 11 & 12 in QlikView

Rounding differences between QV 11 & 12

jrepucci15 — Wed, 01 Mar 2017 18:14:32 GMT

Has anyone noticed that rounding is performing differently in QV11.20 vs QV12.10?

=NUM(102.06500, '#.00') & =num(102.07500, '#.00')

QV version	102.06500	102.07500
QV11.20 SR9	102.07	102.07
QV12.10 SR3	102.06	102.08

Is this a bug or a design difference?

John

Re: Rounding differences between QV 11 & 12

MarcoWedel — Wed, 01 Mar 2017 23:46:36 GMT

Maybe hic‌ can help?

Re: Rounding differences between QV 11 & 12

hic — Tue, 07 Mar 2017 09:27:46 GMT

There is a design difference. Or rather, it is a bug-fix. There was a bug that caused a small unnecessary internal rounding, and that resulted in some corner cases being incorrectly rounded. But it was really only visible in cases where you wanted a tie-breaking, e.g.: Should 0.65 be rounded upwards to 0.7 or downwards to 0.6? So the version 12 behaviour should be more correct.

Note also that 102.065 cannot be exactly represented internally - it has no exact binary representation. Hence, it is really not a tie-breaking issue. The number is always below or above the cutoff limit. See Rounding Errors.

If you want to test how the QIX engine handles real tie-breaks, you need to use exact binary numbers. Then you will find that it always rounds upwards, and that it hasn't changed between v11.2 and v12.