On Fri, 2018-10-12 at 17:34 +0200, Hameer Abbasi wrote: > Hello! > > I’m trying to investigate the exact way ufunc.reduce works when given > a custom dtype. Does it cast before or after the operation, or > somewhere in between? How does this differ from ufunc.reduceat, for > example? >
I am not 100% sure, but I think giving the dtype definitely casts the output type. And since most ufunc loops are defined as "ff->f", etc. that effectively casts the input as well. It might be it casts the input specifically, but I doubt it. The cast will occur within the buffering machinery, so the cast is only done in small chunks. But the operation itself should be performed using the given dtype. - Sebastian > We ran into this issue in pydata/sparse#191 when trying to match the > two where the only thing differing is the number of zeros for sum, > which shouldn’t change the result. > > Best Regards, > Hameer Abbasi > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion
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