Hi, I have added a couple of utilities for floating point comparison, to be used in unit tests mostly, and would like some comments, especially from people knowledgeable about floating point. http://github.com/cournape/numpy/tree/new_ulp_comp The main difference compared to other functions is that they are 'amplitude-independent', and use IEEE-754-specific properties. The tolerance is based on ULP, and two numbers x, y are closed depending on how many numbers are representable between x and y at the given precision. The branch contains the following new functions: * spacing(x): equivalent to the F90 intrinsic. Returns the smallest representable number needed so that spacing(x) + x > x. Spacing(1) is EPS by definition. * assert_array_almost_equal_nulp(x, y, nulp=1): assertion is defined as abs(x - y) <= nulps * spacing(max(abs(x), abs(y))). * assert_array_max_ulp(a, b, maxulp=1, dtype=None): given two numbers a and b, raise an assertion if there are more than maxulp representable numbers between a and b. They only support single and double precision - for complex number, one could arbitrarily define a distance between numbers based on nulps, say max of number of representable number for real and imag parts. Extended precision would be a bit more painful, because of the variety of implementations. I hope that they can give more robust/meaningful comparison for most of our unit tests, cheers, David