[Octave-bug-tracker] [bug #59206] crash during matrix multiplication (Win only)

[Hartmut]

URL:
  <https://savannah.gnu.org/bugs/?59206>

                 Summary: crash during matrix multiplication (Win only)
                 Project: GNU Octave
            Submitted by: hardy
            Submitted on: Wed 30 Sep 2020 12:34:21 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Segfault, Bus Error, etc.
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: 6.0.90
         Discussion Lock: Any
        Operating System: Microsoft Windows

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Details:

I have observed a reproducibly crash of Octave 6.0.90 GUI. It only happens
under Windows 10, not under Linux OS. I have not observed this crash with
Octave 5.2.0 under Windows. (I can also NOT generate this crash with Octave
6.0.90 CLI, but with the CLI version I seem to get a wrong result.)

Here is how to reproduce the crash. The following example code uses functions
(only m-code) from the image package (the current version that is included
within the 6.0.90 Win installer), but I fear that this behavior is not only
due to the image package, but due to core Octave.

1. start the Octave 6.0.90 GUI under Win 10
2. pkg load image, edit imperspectivewarp
   set a breakpoint on line 111 (D = [X(:).......)
3. execute the following simple m-code:


pkg load image
clear
I = ones(649, 1000); % different sizes -> no crash
J = imrotate(I, 5);


4. The code execution will stop at the set breakpoint.
   Make it execute the next line (line 112)
   -> CRASH

The critical code line ( PD = inv(P)*D; ) contains an matrix inverse
calculation and a matrix multiplication. I have seperated this into two
different code lines. The inverse computation works fine then. The crash
happens afterwards during the matrix multiplication. The critical
multiplication has two double type matrices as input, a 3-by-3 and a
3-by-772902 matrix.

When using Octave 6.0.90 CLI version (instead of the GUI version above) I do
not observe a crash. But in this case I seem to get a wrong calculation
result. This can be seen when executing "imshow(J)" after the above m-script.
It should show a white rectangle turned by 5 degrees, buit is has a "noisy
stripe" running through the result image J.

I have no idea what goes wrong here. But it doesn't look good to me, that
Octave crashes reproducibly during a multiplication of two reasonably sized
double matrices (nor that this gives a presumably wrong result).

Can anyone else reproduce this? Any ideas what goes wrong here?




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