[Numpy-discussion] representation of valid float type range
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.e+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.e+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: arch...@mail-archive.com
[Numpy-discussion] Re: representation of valid float type range
Thanks for your answer. I think i understand it - is it that `f64_info.max - f64_info.min` does not fit in float64? because it approximates `2 * f64_info.max`? In that case, I agree with Klaus, linspace should be able to handle this? ___ 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: arch...@mail-archive.com
[Numpy-discussion] Re: representation of valid float type range
I'm not sure I know what that is? do you have a reference I can follow? ___ 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: arch...@mail-archive.com
[Numpy-discussion] Re: representation of valid float type range
I see what you mean, there is, however, some inconsistency on how this is handled, and it's not entirely intuitive ``` _type=np.int8 N=8 np.linspace( start=np.iinfo(_type).min, stop=np.iinfo(_type).max, num=N, dtype=_type, ) =>array([-128, -92, -56, -19, 17, 54, 90, 127], dtype=int8) _type=np.float16 np.linspace( start=np.finfo(_type).min, stop=np.finfo(_type).max, num=N, dtype=_type, ) =>array([-65504., -46784., -28080., -9360., 9360., 28080., 46784., 65504.], dtype=float16) _type=np.float32 np.linspace( start=np.finfo(_type).min, stop=np.finfo(_type).max, num=N, dtype=_type, ) =>array([-3.4028235e+38, -2.4305882e+38, -1.4583529e+38, -4.8611764e+37, 4.8611764e+37, 1.4583529e+38, 2.4305882e+38, 3.4028235e+38], dtype=float32) _type=np.float64 np.linspace( start=np.finfo(_type).min, stop=np.finfo(_type).max, num=N, dtype=_type, ) =>array([nan, inf, inf, inf, inf, inf, inf, 1.79769313e+308]) _type=np.float64 np.linspace( start=0, stop=np.finfo(_type).max, num=N, dtype=_type, ) =>array([0.e+000, 2.56813305e+307, 5.13626610e+307, 7.70439915e+307, 1.02725322e+308, 1.28406652e+308, 1.54087983e+308, 1.79769313e+308]) _type=np.float64 np.linspace( start=-1e291, stop=np.finfo(_type).max, num=N, dtype=_type, ) =>array([-1.e+291, 2.56813305e+307, 5.13626610e+307, 7.70439915e+307, 1.02725322e+308, 1.28406652e+308, 1.54087983e+308, 1.79769313e+308]) _type=np.float64 np.linspace( start=-1e292, stop=np.finfo(_type).max, num=N, dtype=_type, ) =>array([nan, inf, inf, inf, inf, inf, inf, 1.79769313e+308]) _type=np.float16 np.logspace( start=np.finfo(_type).minexp, stop=np.finfo(_type).maxexp, num=N, dtype=_type, base=2, ) =>array([6.104e-05, 1.190e-03, 2.322e-02, 4.529e-01, 8.836e+00, 1.722e+02, 3.360e+03, inf], dtype=float16) _type=np.float16 np.logspace( start=np.finfo(_type).minexp, stop=np.finfo(_type).maxexp, num=N, dtype=_type, base=2, endpoint=False, ) =>array([6.104e-05, 8.211e-04, 1.105e-02, 1.487e-01, 2.000e+00, 2.691e+01, 3.620e+02, 4.872e+03], dtype=float16) _type=np.float64 np.logspace( start=np.finfo(_type).minexp, stop=np.finfo(_type).maxexp, num=N, dtype=_type, base=2, endpoint=False, ) =>array([2.22507386e-308, 2.16653556e-231, 2.10953732e-154, 2.05403862e-077, 2.e+000, 1.94738306e+077, 1.89615038e+154, 1.84626556e+231]) ``` ___ 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: arch...@mail-archive.com
