On Tue, 2022-01-18 at 14:56 +0100, Benoit Gschwind wrote:
> Hello,
>
> I using the following code:
>
> if (PyArray_TYPE(arr1) == NPY_DATETIME) {
> // Ensure datetime64[ms]
> auto tmp =
> reinterpret_cast<PyArrayObject*>(PyObject_CallMethod(reinterpret_cast
> <PyObject*>(arr1), "astype", "(s)", "datetime64[ms]"));
> std::swap(arr1, tmp);
> Py_XDECREF(tmp);
> // Ensure integer
> tmp =
> reinterpret_cast<PyArrayObject*>(PyObject_CallMethod(reinterpret_cast
> <PyObject*>(arr1), "astype", "(s)", "i8"));
> std::swap(arr1, tmp);
> Py_XDECREF(tmp);
> tmp =
> reinterpret_cast<PyArrayObject*>(PyArray_FromArray(arr1,
> PyArray_DescrFromType(NPY_INT64), NPY_ARRAY_IN_ARRAY));
> std::swap(arr1, tmp);
> Py_XDECREF(tmp);
> }
>
> First, if something is wrong with my code let me known. Then I wonder
> if I can have a safe shortcut to avoid converting datetime64 to i8. I
> guess the internal data of datetime64[ms] is i8 thus copying and
> casting the array may be avoided.Yes, you can assume datetime64 is stored as an i8 with the unit and possible byteswapping. Both of which, your initial cast will ensure. The internal data is i8, except for the special NaT value. Code-wise, you can avoid calling `astype`, but if you do (also in python), I suggest to pass `copy=False`, so that it does not copy if it clearly is not necessary (I am hoping to improve on the "clearly" here at some point). The last call again seems to be a no-op? Just the last call with the correct `datetime64[ms]` descriptor could be enough. Cheers, Sebastian > > Thanks by advance > Best regards. > > > _______________________________________________ > 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: sebast...@sipsolutions.net >
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