nested loops in Python
Christian Gollwitzer
auriocus at gmx.de
Thu Sep 8 13:04:24 EDT 2016
Am 08.09.16 um 12:20 schrieb Igor Kozin:
> Why nested loops are so slow in Python? Is it because new contexts are created?
> For more details, see
> http://stackoverflow.com/questions/26611043/numpy-vs-cython-nested-loop-so-slow
> http://stackoverflow.com/questions/39371021/efficient-loop-over-numpy-array
The answers are right there, too - what are you mising? CPython is an
interpreter. For every seemingly simple operation like a[i]=j, a
function pointer is called, the variables contain polymorphic types
which are morphed, etc. The same thing in compiled code is a single
machine instruction. Speed differences of ~100x are normal between
compiled and interpreted code over all dynamic languages.
Christian
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