Mailman 3 November 2022 - NumPy-Discussion

NEP 50 and integers (e.g. uint8 together -1)
by Sebastian Berg 08 Nov '22

08 Nov '22

Hi all, In NEP 50 (https://numpy.org/neps/nep-0050-scalar-promotion.html) my current proposal is that the following: np.array([1, 2], dtype="uint8") + (-1) which currently returns an "int16" array must raise an error. This is because we want to return a uint8 array but the -1 cannot be represented well by -1. The same should also happen for a value of 300 (rather than -1). My main question is not about making this an error though. The question is whether the following two cases should also error: uint8_arr = np.array([1, 2], dtype="uint8") uint8_arr[0] = -1 or: np.array([-1], dtype=np.uint8) (In practice these currently give the maximum integer with well defined integer overflow.) Note that the call `np.uint8(-1)` could be a special case here! The reason I ask is that my PR: https://github.com/numpy/numpy/pull/21875 currently introduces the new error without changing the other cases and this requires adding a full new conversion path. If we want to change that anyway (or keep things aligned), I could simplify the logic in the PR. Cheers, Sebastian

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New API for testing custom array containers
by Nathan 04 Nov '22

04 Nov '22

Hi all, I just opened a PR (https://github.com/numpy/numpy/pull/22533) that makes a minor modification to the numpy API. The PR creates numpy.testing.overrides, which contains some helpers for downstream projects who want to test types that implement __array_function__ and __array_ufunc__. See the discussion in https://github.com/numpy/numpy/issues/15544 for more context. -Nathan

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How does Numpy build system detect the change of .c source file?
by 腾刘 02 Nov '22

02 Nov '22

Hi everyone! I 'm here again. Recently I 'm trying to understand the C code with output-debug method, inserting many print statements. I was doing well with it until one day: I changed a file called loops_utils.h.src located in numpy/core/src/umath by inserting some "printf", but after I re-built the Numpy from source, the changes didn't apply. Specifically, I added: printf(" ??????? "); in line 80, but after re-building it didn't output "??????". I found that when I ran "python setup.py build_ext --inplace", the output info seemed to tell me that nothing has been compiled, because normally when something changed, it will output: > x86-64-conda-linux-gnu-cc: xxxxxx.dispatch.c What's more interesting is that: after I changed the file loops_arithm_fp.dispatch.c.src, and then rebuilt, the change to loops_utils.h.src applied, with the screen full of "??????". I tested it for many times that each time I modify loops_utils.h.src, and the change doesn't apply after re-building; while after I modify loops_arithm_fp.dispatch.c.src, the change to loops_utils.h.src starts to apply. It seems to be related to how build system detects the change, I guuess. Can someone explain why this will happen or point out what I 've missed?

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