Bug Fixed-point in LabView?

Hello

I am currently working on a project in LabView and met FPGA something weird that looks like a bug, but it could also just be me not well understand how fixed-point numbers are supposed to work. I work in LabView 2010 Pro (32-bit 10.0f2) on Win 7 Ent. 64 bit.

The problem I have is that when I try to add some numbers together I get unexpected answers, which obviously makes the code very unreliable.

For example: If you try to add 0.50002 with - 0.49998, you expect something around zero, but instead, you get like 3.99999... Am I missing something here? I saw this on several numbers around zero. Fixed points do not work around zero?

I should add that I just tried it on the local computer and not on the FPGA, but I don't see that would make a difference. The two entries are updated to 'Adapt to the entered data' and the output is "Adapt to the source", the Add function is also set to "Adapt to the source" and I tried the envelope and saturate... I also tried with fixed bits rather than adapt to the data entered on the inputs etc with no luck.

Can anyone shred some light on this please? Is it just me or is it really a bug or just as fixed-point numbers are supposed to work?

Thank you!

/ Joel

It is not a bug.  If you develop the indicator displays the result, you will see that there is an exponent of-5 at the end (e-5 = 10 ^-5).    So that is to say the answer is 4 * 10 ^-5 or 0.00004, which is pretty close to 0.

Tags: NI Software

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