calculation error for floor function

Hello all, when I was trying for >>floor(2.3 * 50) , I was getting 114 where I suppose to get 115. Is this due to precision issue? and How to fix it?

[Shlomo Geva]

Well, check this code: floor(p/65536) floor() does not handle correctly uint32 values of p > 4294934528 which is well within uint32 range. It is not even returning a value in the expected range 0 to 65535

>> p=uint32([4294934527, 4294934528, 2^32-1]);floor(p/65536)

ans =

1×3 uint32 row vector

   65535   65536   65536

Answer 1

[Sebastian]

If you have the Symbolic Math Toolbox, try this:

x = vpa(2.3 * 50)
x =
  115.0
x = floor(x)
x =
  115

Answer 2

[Jan]

Yes, this is an effect of the limited precision of the IEEE754 floating point standard. See http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F . You find a lot of corresponding question, when you search e.g. for "faq 6.1".