[Python-Dev] [numpy wishlist] Interpreter support for temporary elision in third-party classes (original) (raw)

Nikolaus Rath Nikolaus at rath.org
Fri Jun 6 03:15:42 CEST 2014

Nathaniel Smith <njs at pobox.com> writes:

Such optimizations are important enough that numpy operations always give the option of explicitly specifying the output array (like in-place operators but more general and with clumsier syntax). Here's an example small-array benchmark that IIUC uses Jacobi iteration to solve Laplace's equation. It's been written in both natural and hand-optimized formats (compare "numupdate" to "numinplace"):

https://yarikoptic.github.io/numpy-vbench/vbvbapp.html#laplace-inplace numinplace is totally unreadable, but because we've manually elided temporaries, it's 10-15% faster than numupdate.

Does it really have to be that ugly? Shouldn't using

tmp += u[2:,1:-1] tmp *= dy2

instead of

np.add(tmp, u[2:,1:-1], out=tmp) np.multiply(tmp, dy2, out=tmp)

give the same performance? (yes, not as nice as what you're proposing, but I'm still curious).

Best, -Nikolaus

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