Possible Bug in equality test components

Each of the test components (Greater/Less than or equality) seem to produce erroneous results unless the values are filtered by a notes panel.

I think the result should be TRUE when zero is tested for equality against zero no matter where the zeros are coming from.

If this isn't a bug, would someone please enlighten me as to why these tests produce different results.

Grasshopper Build 0.9.0076

Attachments:

zeroNOTzero.jpg, 81 KB
zeroNOTzero.gh, 13 KB

Replies to This Discussion

Permalink Reply by Richard Schaffranek on October 12, 2017 at 6:06am

Hi there,

it is not realy a bug.

Numbers in computers have a limited ammount of precission. I don't want to go into detail about that -> check wikipedia for float / double...

In Grasshopper you can specify the display precission of numbers under preferences. When you connect a number to a panel it is acctualy converted into a string with that precission. e.g.:

0.000000000000000000001 will be represented as 0.0 string in the panel but of course it is not equal to 0.

But as you convert it to a String in the panel and than convert it to a number for comparision again the string 0.0 will be converted to the number 0.0 and all of a sudden 0.000000000000000000001 equals 0.0...

So what acutally happens through the panel is a loss in precission.

Permalink Reply by Andrew Heumann on October 12, 2017 at 12:03pm

http://www.grasshopper3d.com/forum/topics/floating-point-error-why-...

Permalink Reply by Michael Pryor on October 12, 2017 at 12:09pm

The best way to test equality on doubles is to ask if the Absolute Value of |A-B| < tolerance value. If true they are equal(enough) if false they are not equal(enough) .

Permalink Reply by Gabe Krause on October 12, 2017 at 3:30pm