Copy function

[davidbsp]

Hi @tzikis and @eecharlie

I've been playing around with the MatrixMath library, and I have a very specific issue with the Copy function, which is giving me a huge headache:

Here is a minimal example:

  float X[10][40][3];    //an array of 10 matrices (40x3)
   
   //just fill it with 5's:
   for(int i=0; i<10; i++){
       for (int j=0; j<40; j++){
           for (int k=0; k<3; k++){
               X[i][j][k] = 5.0;
           }
       }
   }    

   float Q [10][40][3];    
   
  //now, I just want to copy the 1st matrix of X (located in X[0]) to Q[0]:
   Matrix.Copy( (float*)X[0], 3, 40, (float*)Q[0] );
   Serial.println("Copy done");

While the compiler doesn't complain about this code, the program segfaults after the copy operation...
Can you perhaps let me know why, and how can I solve this?

I also noticed that the Copy function receives n (cols) first and m (rows) after, as opposed to all the other functions in the library. Do you know the reason for this design choice? I would recommend to change the order for easiness of use.

Thanks!

[tzikis]

Hi @davidbsp to be honest, I've got no clue! See, we're not the original developers of this library, we just put it up on github because a few of codebender's users wanted to use it for Arduino. The original library was bundled along with Wiring (wiring.org), which is a project the Arduino was based on

[eecharlie]

I'm replying quickly without having had a chance to test the code myself. Thank you for providing a self-contained example; this should be built into a unit test if it turns out to be bad behavior. I never tested the code on arrays of matrices. Are you sure about your indexing order? My intuition is that the matrix axes should be the last two indices, not the first two. Charlie On Jan 11, 2018 9:59 AM, "Vasilis Georgitzikis" <[email protected]> wrote: Hi @davidbsp <https://github.com/davidbsp> to be honest, I've got no clue! See, we're not the original developers of this library, we just put it up on github because a few of codebender's users wanted to use it for Arduino. The original library was bundled along with Wiring (wiring.org), which is a project the Arduino was based on — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AACQGQtk7SFNI3SjEdl5Nvfni-IpSqutks5tJiHRgaJpZM4Ra42w> .

[fakedrake]

Hey, your code seems fine at a first glance. I am wondering how you get SIGSEGV on Arduino, being that the device is not running an OS to raise the signal. - Do you mean that the signal is raised during the building/flashing process? - Do other methods from the library work? - Which Arduino model are you using?

[davidbsp]

Hi! It seems that my problem was memory management in the board.
Although I provided a minimal code, I was flashing the board with other stuff as well.
The code compiles, the board flashes without any issue. However, nothing happened when executing.

Just for reference:

• there's nothing wrong with the index order.
• "segfaults" was a bad choice of words, what I meant was: the board would block (red light flash) when executing the code.
• other methods from the library work.
• I am using a Particle Photon IoT device -- It has 128k of RAM.

When I erased other large variables (10 to 12 "float X[10][40][3]" 3D arrays), things started working again.