As Kostya already commented, this is rounding error. The error is well within the acceptable range for IEEE-754 floating point multiplication, since the inaccuracy is still only 2 parts in 10^13.
Still, it is a little embarrassing, considering that Python also implements IEEE-754, and gets it exactly right: 100.0 * 0.0254 yields 2.54. I wonder which rounding modes (there are 5 different choices in IEEE-754) Python and Android (resp.) chose to implement. In fact, a few casual Google searches, such as "floating point rounding Android", yield nothing about what choices they made when implementing IEEE-754. It doesn't even yield who is responsible for this: the OEM or the authors of Android itself. BTW: I didn't check too thoroughly, but it looks to me like despite appearances, 0.254 is not exactly representable in binary -- it has lots of trailing zeros followed by yet more digits. On Sep 3, 2:59 pm, Churky <[email protected]> wrote: > When Performing a division or multiplication. The value does not equal > to the arithmetic. > example i have: > > double value = 100 * .0254; > > in real life equals = 2.5908 > > While android calculates it to: 2.5907999999999998 which is wrong. > > I have verified this in the emulator using multiple machines, and > multiple version of android. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
