Simotion D445-2 DP/PN threading doubts ...

Hello there,

I am using a for loop so as to get a polyfit aprox curve like this:

res := 0.0;
FOR i:=0 TO 19 DO
    res := res + coef[i] * EXPT(pos, INT_TO_LREAL(i));
END_FOR;

Thing is that, sometimes the result of this operation (that should be among 0 and 1000) gives me, for example, 30000M or so ..... it is quite random .... I have traced it and the "glitch" is quite visible and makes Simotion come to stop due to I try to asign it to an INT tag:

pos_to_plc := LREAL_TO_INT(res);

I am wondering if for some reason that FOR is "left" by the task so as to make anothe interrupt and when it comes back it just "jump" out that FOR leaving a non-finished value of res....

And here is where que question comes... does Simotion have real multithread (real multicore)? I mean, this FOR was set in the background task in the beginning; then I tried in a synchronous task but have the same glitchy results ...

Having the FOR operation in a synchronous task (I had it in a 1ms synchronous operation task) maybe would have some sense, because could happen that while in the synchronous task the "FOR" is being made ... if exists real multithread, pos_to_plc would be assigned something like LREAL_TO_INT(300000000000.0), for example as the FOR loop is being made (and also cause Simotion go to Stop ...)

Where could I find a description of how threading and tasks exactly works ?

Thanks in advance