Smallest positive float64 number

Question

I need to find a numpy.float64 value that is as close to zero as possible.

Numpy offers several constants that allow to do something similar:

• np.finfo(np.float64).eps = 2.2204460492503131e-16
• np.finfo(np.float64).tiny = 2.2250738585072014e-308

These are both reasonably small, but when I do this

>>> x = np.finfo(np.float64).tiny >>> x / 2 6.9533558078350043e-310 

the result is even smaller. When using an impromptu binary search I can get down to about 1e-323, before the value is rounded down to 0.0.

Is there a constant for this in numpy that I am missing? Alternatively, is there a right way to do this?

Answer 1

Use np.nextafter.

>>> import numpy as np >>> np.nextafter(0, 1) 4.9406564584124654e-324 >>> np.nextafter(np.float32(0), np.float32(1)) 1.4012985e-45 

Answer 2

2^-1075 is the smallest positive float. 2^-1075 = 5.10^-324