Originally posted by: RuiFig

Hi, 

I need help to define a specific moment to start an activity.

I'm developing a scheduling model for a job shop, and i have certain products that dont need to be processed in certain machines.

I thought that if i put that activities in to be "executed " in the instant zero with a duration of zero it would solve my problem. 

Can someone help me to solve this problem or help me to find a better solution ? 

Hi,

why not relying on optional intervals ?

See example in CPLEX_Studio1210\opl\examples\opl\sched_optional

regards

Originally posted by: RuiFig

I will try that, i also have another doubt.

I have two machines that can not work at the same time, how do i model that situation ? 

I'm new to cplex, so sorry for any dumb question. 

Hi,

you may use noOverlap

OPL constraint (scheduling) used to prevent intervals in a sequence from overlapping and (optionally) to enforce a minimal distance between consecutive intervals.

 

 

Originally posted by: RuiFig

i already use the nooverlap constrain within one machine like this 

forall(m in mach)

nooverlap(mchs[m],tt[m],1);

but i dont wont machine 1 and 3 to work ate the same time for exemple.

Hi,

then a sequence could help:

using CP;

range r=1..3;

dvar interval itvs[r] size 2;
dvar sequence seq in    all(i in r:i!=2) itvs[i];

 

minimize max(i in r) endOf(itvs[i]);
subject to
{
  noOverlap(seq);
}

execute
{
  writeln(itvs);
}

which gives

// solution with objective 4
 [<1 0 2 2> <1 0 2 2> <1 2 4 2>]

regards

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