double limit? or a bug?

[HaveF]

I build a table with double type like this:

but get result like this(look at the last digital, the number is not the same!):

Did I do something wrong?
doublelimit.knar.knwf (4.0 KB)

KNIME version 3.6.2

[stelfrich]

Hi @HaveF,

Thank you for providing the workflow! I was able to reproduce the issue and will look into this…

Best,
Stefan

[HaveF]

hi @stelfrich

Thanks for your invest. I suppose it affects lots of modules.

I find this bug? in a database reader, it read the wrong double number. In order to reproduce this, I use the table above to report issue.

[moritz.heine]

Hi,

this is a limitation of double and how it represents numbers in a computer.

Short explanation:
Double stores values as decimals with a single digit before the decimal-point + exponent. Thus, it has a limited number of bits (52bits) to represent the value which yields a loss in the precision.

There is unfortunately not much we can do about that.

Cheers,
Moritz

[HaveF]

Do like your short explanation…

Btw, could the related module throw some warnings about this? I believe it would be helpful

[moritz.heine]

That’s a good point, I created a ticket for that in our bug tracking system.