Could it be you need to get a handle on the "epsilon machine"? On Wed, 29 Dec 2021, 9:21 am , <alejandro.giacome...@gmail.com> wrote:
> I am getting an interesting result, and I'm wondering if anyone would care > to give me some intuition of why. > > The example is simple enough, I want to get a range of values that are > representable by a type: > > ```python > f64_info = np.finfo(np.float64) > valid_range = np.linspace( > start=f64_info.min, stop=f64_info.max, num=10 > ) > valid_range => array([ nan, inf, inf, > inf, > inf, inf, inf, inf, > inf, 1.79769313e+308]) > ``` > > The minimum value is representable by the type, I can see it: > > ```python > f64_info.min => -1.7976931348623157e+308 > ``` > > I thought that maybe the valid range cannot start with the minimun value, > so I've tried a few alternatives: > > ```python > > valid_range = np.linspace( > start=f64_info.min + f64_info.eps, stop=f64_info.max, num=10 > ) > valid_range => array([ nan, inf, inf, > inf, > inf, inf, inf, inf, > inf, 1.79769313e+308]) > > > valid_range = np.linspace( > start=f64_info.min + f64_info.tiny, stop=f64_info.max, num=10 > ) > valid_range => array([ nan, inf, inf, > inf, > inf, inf, inf, inf, > inf, 1.79769313e+308]) > ``` > > I thought maybe the range is too wide, but I can do this: > > ```python > valid_range = np.linspace( > start=0, stop=f64_info.max, num=10 > ) > valid_range => array([0.00000000e+000, 1.99743682e+307, 3.99487363e+307, > 5.99231045e+307, > 7.98974727e+307, 9.98718408e+307, 1.19846209e+308, > 1.39820577e+308, > 1.59794945e+308, 1.79769313e+308]) > > ... > > valid_range = np.linspace( > start=f64_info.tiny, stop=f64_info.max, num=10 > ) > valid_range => array([2.22507386e-308, 1.99743682e+307, 3.99487363e+307, > 5.99231045e+307, > 7.98974727e+307, 9.98718408e+307, 1.19846209e+308, > 1.39820577e+308, > 1.59794945e+308, 1.79769313e+308]) > > ... > > f32_info = np.finfo(np.float32) > valid_range = np.linspace( > start=f32_info.tiny, stop=f32_info.max, num=10, dtype=np.float32, > ) > valid_range => array([1.1754944e-38, 3.7809150e+37, 7.5618299e+37, > 1.1342745e+38, > 1.5123660e+38, 1.8904575e+38, 2.2685490e+38, > 2.6466405e+38, > 3.0247320e+38, 3.4028235e+38], dtype=float32) > > ``` > > I know that linear space is arbitrary, and perhaps not that useful. In > fact this is valid: > > ```python > valid_range = np.logspace( > start=f64_info.minexp, stop=f64_info.maxexp, num=10, base=2, > endpoint=False > ) > valid_range => array([2.22507386e-308, 8.67124674e-247, 3.37923704e-185, > 1.31690901e-123, > 5.13207368e-062, 2.00000000e+000, 7.79412037e+061, > 3.03741562e+123, > 1.18369915e+185, 4.61294681e+246]) > ``` > > But I'm still confused on why linear space is invalid > > Thanks! > _______________________________________________ > NumPy-Discussion mailing list -- numpy-discussion@python.org > To unsubscribe send an email to numpy-discussion-le...@python.org > https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ > Member address: seb...@gmail.com >
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