python numpy机器epsilon
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python numpy machine epsilon
提问by Bob
I am trying to understand what is machine epsilon. According to the Wikipedia, it can be calculated as follows:
我试图了解什么是机器 epsilon。根据维基百科，它可以计算如下：
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.float32class. Can anybody help with modifying the function?
但是，它仅适用于双精度数。我有兴趣修改它以支持单精度数字。我读到可以使用 numpy，尤其是numpy.float32class。有人可以帮忙修改函数吗？
采纳答案by ali_m
An easier way to get the machine epsilon for a given float type is to use np.finfo():
获取给定浮点类型的机器 epsilon 的更简单方法是使用np.finfo()：
print(np.finfo(float).eps)
# 2.22044604925e-16
print(np.finfo(np.float32).eps)
# 1.19209e-07
回答by Claudiu
It will already work, as David pointed out!
正如大卫指出的那样，它已经可以工作了！
>>> 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
回答by Ullen
Another easy way to get epsilon is:
获得 epsilon 的另一种简单方法是：
In [1]: 7./3 - 4./3 -1
Out[1]: 2.220446049250313e-16
