[open] Crash During Experiment (Due to Synchronization Error?)

thomas00

Hi,

I have been running an experiment for a while, but today Open Sesame crashed right in the middle of it with the following error message:

Error while executing inline script

phase: run

item: end_EEG

line: 114

exception message: internal 32-bit counter passed through zero, please resynchronize ( call .synch() once again )

exception type: Eggog

Traceback (also in debug window):

File "dist\libopensesame\inline_script.py", line 154, in run

File "", line 3, in

File "C:\Documents and Settings\EGI\Desktop\opensesame\egi\simple.py", line 114, in ms_localtime

Eggog: internal 32-bit counter passed through zero, please resynchronize ( call .synch() once again )

I was recording my 25th participant when the crash occurred, and this is the first time I have seen this error (no problems whatsoever before). I use the current version of the software, connected to an EGI Net Station EEG setup. I have been unable to recreate the error after the failed session had ended.

Before the failed session, a colleague of mine had dis- and reconnected the Ethernet cable connecting the computer running Open Sesame with the EGI system. Some TCP/IP related settings had been changed and restored, but I guess this shouldn't be the issue seeing as how the problem has disappeared?

I have no idea what may have caused the error, and therefore don't know how to prevent it from happening again. Any help regarding potential causes (and possible solutions ... ) would be greatly appreciated!

Thanks in advance!

Thomas

Edit: Formatting

sebastiaan

Hi Thomas,

This error comes from the Python library of your EEG set-up (egi), so for a definitive answer it's best to ask the developers of that library. However, because the error message is quite informative, I'll venture a guess.

It seems the EEG device has an internal timer that uses a 32 bit timestamp. This means that it cannot go above 4,294,967,295 (=2^32-1). When that happens, the timer will overflow and go back to 0. And that seems to be what happened in your case. Because the timer can run for a long time without an overflow occurring, this is a pretty rare event--but it should happen every once in a while.

There's probably a function that you can call to reset the counter to 0 at the start of your experiment, to avoid this problem. That could be the synch() function that is referred in the error message, but you should be able to find this in the documentation of the egi library (which is not part of OpenSesame).

Hope this helps and happy holidays!

Cheers,
Sebastiaan

thomas00

Hi Sebastiaan,

Thank you very much for your quick reply! This will definitely prove to be helpful!

Best,
Thomas

Edwin

BTW: a similar bug happened on YouTube recently.

sebastiaan

Haha, that's hilarious.