c2c-oerpscenario team mailing list archive

[Marco Dieckhoff <882036@xxxxxxxxxxxxxxxxxx>]

That's not a python bug, it is a ever-present problem when dealing with
float values, in every programming language.

As all information is, floats are represented as bits. As you have a fixed amount of bits in a float value, you have a finite number of possible representations, compared to infinite numbers and decimals in the real world numbers.
As described in http://en.wikipedia.org/wiki/IEEE_754-2008, in order to allow for a maximum of representable values, rounding issues can apply:

round() is a test for >= 0.5 (or later decimals, depending on
implementation)

But 2.675 is represented as a bit setting that is actually 2.67499999...
So the test for >= fails.

compare http://docs.python.org/tutorial/floatingpoint.html
That is also mentioned in the accounting mail linked above.

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https://bugs.launchpad.net/bugs/882036

Title:
  rounding error

Status in OpenERP Server:
  New

Bug description:
  Concerns 6.0 and trunk.
  If you define a precision of 0.01, the rounding of 0.125 must be 0.13 and not 0.12. The error is in the call of the format string "%.2f"%val which introduces a mathematical error. The round function must be called to apply the correct rounding before formatting the string. It should be:
  "%.2f"%round(val*100)/100
  Fix class digits_change of class float in the server. BUT fix also the gtk client AND web client as they all have that error (I let you find the right line)

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