Good to hear this, I'll be glad to take a look. The fact that the result is returned in a second when run from the CLI is weird, and seems to exclude the scenario I was depicting. Anyway, if you're sure you're running on pretty the same input data, I wonder if the webserver puts a maximum threshold to memory consumption together with total execution time.

you can see my pseudocode above, there is "and warn" part if system was not successfully executed

I hoped this was only some kind of example! First of all, maybe you'd use "or warn" instead of "and warn", otherwise you're getting warns only if the system() runs ok; moreover, I hope you don't deduce that your program is running smoothly only from the fact that the warn is not printed out, because if the webserver is killing your process you're not likely to arrive that far. Do you see any actual output past the system() line?

Anyway, I'll wait to see some more code.