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## [Octave-bug-tracker] [bug #57805] Some array permutations are much slowe

**From**: |
Michael Leitner |

**Subject**: |
[Octave-bug-tracker] [bug #57805] Some array permutations are much slower than others |

**Date**: |
Fri, 14 Feb 2020 04:26:46 -0500 (EST) |

**User-agent**: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0 |

Follow-up Comment #3, bug #57805 (project octave):
Interesting, multithreading benefits specifically the large permutations,
where data are definitely out of cache. That puzzles me. So comparing the
single-threaded values, octave has a larger dependence on the particular
permutation than matlab, and while for the easier permutations octave and
matlab are about on par, octave suffers with the harder permutations. Perhaps
I find some time and can jot down a simple test implementation of permute that
is agnostic of the interpretation of the data (that is, just copying around
strings of bytes) and see how close the octave values are to the optimum.
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