bugGNU Octave - Bugs: bug #39788, Vectorized computation of Sigmoid...


bug #39788: Vectorized computation of Sigmoid function causes segfault

Submitted by:  None
Submitted on:  Wed 14 Aug 2013 08:14:16 PM UTC  
Category:  Interpreter Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Segfault, Bus Error, etc.
Status:  Duplicate Assigned to:  None
Originator Name:  Tomáš Zaoral Originator Email:  -email is unavailable-
Open/Closed:  Closed Release:  3.6.4
Operating System:  GNU/Linux

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Thu 15 Aug 2013 11:59:00 AM UTC, comment #5:

No, you are using the term itself correctly, but you have just demonstrated that you don't understand what mathematical operation is actually being performed by your code. Please ask on the help mailing list for support and tips, and please mention up front that it is a homework assignment if you do want to learn and not just get a quick answer :)

Also read http://www.gnu.org/software/octave/doc/interpreter/Arithmetic-Ops.html

Closing this bug and marking as a duplicate that I reported earlier. I'm sorry that it does crash for you, but it's nothing that Octave is causing.

Mike Miller <mtmiller>
Project Administrator
Thu 15 Aug 2013 11:02:12 AM UTC, comment #4:

I run Octave on Linux Mint 13, which is built upon Ubuntu repositories.

I installed with command:

sudo apt-get install octave gnuplot

In terms of vectorization, I admit that I am newbie to this term, so I probably misused it here. However, [1 2 3; 1 2 3; 1 2 3] / [1 2 3; 1 2 3; 1 2 3] = [1 1 1; 1 1 1; 1 1 1] then I don't see why my implementation of sigmoid function should be erroneous.

I will try out http://pad.lv/1156575 as soon as I get home.

Yes, it is a coursera.org ML (Standford) exercise.

Thu 15 Aug 2013 03:29:02 AM UTC, comment #3:

I can confirm what you report, but it is not a bug in Octave. Rather there is a bug in your attempt to vectorize this routine. Unfortunately, since Octave crashes on your OS in this situation, I can see why you might think it's a bug in Octave.

Are you running Octave on Ubuntu? If so, please go to http://pad.lv/1156575 and click on the "Does this bug affect you?" link.

As to your function, please ask on the help list if you're having trouble figuring out how to properly vectorize. Also read the Octave manual for the difference between the "/" and "./" operators. Is this a homework problem for a machine learning class?

Mike Miller <mtmiller>
Project Administrator
Wed 14 Aug 2013 09:36:47 PM UTC, comment #2:

Works for me as well, 3.6.4 on Ubuntu Linux.

Rik <rik5>
Project Administrator
Wed 14 Aug 2013 08:44:01 PM UTC, comment #1:

Can't reproduce. How did you obtain Octave? Did you build it yourself?

Jordi Gutiérrez Hermoso <jordigh>
Project Administrator
Wed 14 Aug 2013 08:14:16 PM UTC, original submission:



>> z

z =

-1000000 0 1000000
-1000000 0 1000000

>> sigmoid(z)

    • On entry to DLASCL parameter number 4 had an illegal value


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   bug dependencies.

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    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    Thu 15 Aug 2013 11:59:00 AM UTC mtmiller StatusWorks For Me => Duplicate
        Open/ClosedOpen => Closed
        Dependencies- => Depends on bugs #38575
    Wed 14 Aug 2013 09:37:05 PM UTC rik5 Carbon-CopyRemoved 72865 => -
    Wed 14 Aug 2013 08:44:01 PM UTC jordigh StatusNone => Works For Me

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