I am trying to understand what is machine epsilon. According to the Wikipedia, it can be calculated as follows:
def machineEpsilon(func=float): machine_epsilon = func(1) while func(1)+func(machine_epsilon) != func(1): machine_epsilon_last = machine_epsilon machine_epsilon = func(machine_epsilon) / func(2) return machine_epsilon_last However, it is suitable only for double precision numbers. I am interested in modifying it to support also single precision numbers. I read that numpy can be used, particularly numpy.float32 class. Can anybody help with modifying the function?
3 Answers
An easier way to get the machine epsilon for a given float type is to use np.finfo():
print(np.finfo(float).eps) # 2.22044604925e-16 print(np.finfo(np.float32).eps) # 1.19209e-07 Another easy way to get epsilon is:
In [1]: 7./3 - 4./3 -1 Out[1]: 2.220446049250313e-16 It will already work, as David pointed out!
>>> def machineEpsilon(func=float): ... machine_epsilon = func(1) ... while func(1)+func(machine_epsilon) != func(1): ... machine_epsilon_last = machine_epsilon ... machine_epsilon = func(machine_epsilon) / func(2) ... return machine_epsilon_last ... >>> machineEpsilon(float) 2.220446049250313e-16 >>> import numpy >>> machineEpsilon(numpy.float64) 2.2204460492503131e-16 >>> machineEpsilon(numpy.float32) 1.1920929e-07 
