Info: Biggest mistake with threading

[Bot-Factory 602]

Hi Guys,

 

this is mainly for everyone who just started with threading. But there is one error I have seen a couple of times.

 

Let's say you want to loop through a list and then process the list item in a separated thread.

 

WRONG Way of doing it:

set(#counter,1,"Global")

loop(10) {
    thread {
        TestThread(#counter)
    }
    increment(#counter)
}

 

define TestThread(#row) {
          comment("CODE")
}


This is a timing problem. When you do it like that, the increment command will sometimes increase the global #counter variable, before the thread has received the data.
So instead of:
1-2-3-4-5-6-7-8-9-10
You will end up with something like:
1-3-3-4-5-6-6-8-8-10

So it will mess up the whole thing. 

There are now multiple ways of "fixing" this. 

You could add a wait before the increment to slow everything down. This could work if your threads run long enough. But for very quick stuff, this would slow the whole thing down.

A better approach is:

set(#counter,0,"Global")
loop(10) {
    TestThread(#counter)
    increment(#counter)
}

define TestThread(#row) {
    thread {
          comment("CODE")
    }
}


Hope this will help some of you. Because this threading stuff can be tricky to troubleshoot sometimes. 


Dan