Possible Bug with Rounding

[spindive]

Hello Fabric Team,

We are seeing some inconsistencies when using the ROUNDDOWN function. For example, when creating a measure/calculated column with this hardcoded formula: 

(1.8-rounddown(1.8, 0))=0.8

The formula evaluates to TRUE, which is correct as 0.8=0.8

However, when we evaluate:

(2.8-rounddown(2.8, 0))=0.8

The formula evaluates to FALSE, which in our opinion is incorrect as 0.8=0.8, no matter how we got there. Please see below for our test tables:

On a call with the Fabric support team (ticket #2404220040008712), we tried and found that the same problem exists even when:

1. We don't harcode the number and use references (columns, other measures) instead
2. We use INT() or TRUNC() instead of ROUNDDOWN()
3. We move the formula to Power Query and use Number.RoundDown instead
4. We use strictly equal == or other operators like <= and >=

Our current workaround is to put a ROUND on the left side of the formula, that seems to overcome the issue.

Lastly, not sure if this will help you investigate, but we noticed that the breaking point is between 1.8 and 1.9. Where if the decimal number is below or equal to 1.8 the formula will work properly, while it will not work if the decimal number is above 1.9, with the following exception: For some reason, 1.99 and 1.9999 works (evaluates to TRUE), but 1.9, 1.999, 1.99999 and beyond do not.

Looking forward to hearing back from you!

Regards,

Felix

[v-xiaoyan-msft]

Hi @spindive,

We saw that you opened a support ticket and the ticket engineer has higher access to investigate this issue than the community support engineer, I would like to know more about this ticket, did they inform you that this issue was acknowledged as a bug and reported internally?

Best regards.
Community Support Team_Caitlyn

[spindive]

Hi @v-xiaoyan-msft,

The ticket support staff were not able to solve the ticket and they asked us to contact Microsoft Partners (3rd party paid services) or through this community. We did ask them to escalate internally but they said they cannot do that.

Thanks,

Felix