bugGNU Octave - Bugs: bug #50796, calling find on diagonal matrix is...


bug #50796: calling find on diagonal matrix is slower than full matrix

Submitted by:  Carnë Draug <carandraug>
Submitted on:  Thu Apr 13 13:19:14 2017  
Category: PerformanceSeverity: 3 - Normal
Priority: 5 - NormalItem Group: None
Status: NoneAssigned to: None
Originator Name: Open/Closed: Open
Release: devOperating System: GNU/Linux

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Sat Apr 15 14:02:14 2017, comment #2:

I forgot to mention that this was identified on this

stackoverflow question http://stackoverflow.com/a/43393446/1609556

where I mention that find has special cases for several data types and it is missing diagonal matrices. It's just weird that it takes so much more time so maybe there is something else going on.

Carnë Draug <carandraug>
Project Member
Thu Apr 13 14:14:23 2017, comment #1:

The attached script produces (using function speed)

So it seems the problem is with doubles, as booleans are close to the optimal. I am puzzled by the negative order of the boolean full case.

(file #40391)

Juan Pablo Carbajal <juanpi>
Thu Apr 13 13:19:14 2017, original submission:

I though this was because find converts a diagonal to a full matrix internally, but even if calling full ourselves before find, it's still much faster so I am no longer sure:

Carnë Draug <carandraug>
Project Member


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Attach File(s):

Attached Files
file #40391:  find_timeit.m added by juanpi (829B - text/x-objcsrc)


Depends on the following items: None found

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  • -unavailable- added by juanpi (Updated the item)
  • -unavailable- added by carandraug (Submitted the item)

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    Follows 1 latest change.

    Date Changed By Updated Field Previous Value => Replaced By
    Thu Apr 13 14:14:23 2017juanpiAttached File-=>Added find_timeit.m, #40391

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