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DOC: how to find your way in the code, for instance the dot function #15567

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tachukao opened this issue Feb 14, 2020 · 3 comments
Open

DOC: how to find your way in the code, for instance the dot function #15567

tachukao opened this issue Feb 14, 2020 · 3 comments
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04 - Documentation component: numpy._core sprintable Issue fits the time-frame and setting of a sprint

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@tachukao
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I've been trying to figure out how np.dot works for multi-dimensional arrays (dimension > 2). I couldn't quite locate where this is specified in the source code. I assume this is done in C with multiple calls to cblas gemm. Any pointers will be most appreciated!
@mattip
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mattip commented Feb 14, 2020

Assuming you are using a BLAS backend, it is

array_dot -> PyArray_MatrixProduct2, which creates an iterator and calls dot. That function is actually part of the descr, and is found as dot = PyArray_DESCR(out_buf)->f->dotfunc on line 993. So what is dotfunc ? It is a PyArray_DotFunc, defined by templated code in https://github.com/numpy/numpy/blob/v1.18.1/numpy/core/src/multiarray/arraytypes.c.src. For float32, float64, the function used is this one, for complex this one, and for ints the non-blas one. Then those functions are assigned to the correct slot in some more templated code. I have not show all of the variants in arraytypes.c.src, but this should get you started.

While not truly an issue per-se, I think we should discuss adding a "how to browse the code" section to the documentation with this as an example, so I am changing the title and marking this "Documentation"

@mattip mattip changed the title dot function source code DOC: how to find your way in the code, for instance the dot function Feb 14, 2020
@InessaPawson InessaPawson added the sprintable Issue fits the time-frame and setting of a sprint label Jan 6, 2022
@Kai-Striega
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Maybe the documentation should also link to this video?

@tachukao
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thanks @mattip and @Kai-Striega for the pointers!!

@tachukao tachukao reopened this Jan 26, 2023
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@mattip @tachukao @Kai-Striega @InessaPawson