Help with scheduling of tasks problem&In-Reply-To=mailman.69.1149662727.939.mozart-users@ps.uni-sb.de

[Filip Konvička]

Hi Tim,

this is kind of dilemma for me, I see that people on this list are a bit 
careful about not spoiling homeworks :-) I'm going to help you a bit though.

Let's use the 3rd possibility :-) (Of course there are many more.) I see 
that you constrain a task to a specified time interval (using something 
like "TestVal=<:Start.P" etc.). Additionaly, you want to exclude all 
tasks from some interval, say, "I". For each task, you could specify - 
before you search for a solution - that it occurs either before or after 
I. Now there are 2^n combinations, see? So we have 2^n problems, all of 
which differ in which tasks must occur before I and which occur after I. 
You already know how to constrain a task to a specified interval, so you 
should be able to solve these 2^n problems and pick your favorite solution.

The nice thing about Oz is that you can make a non-deterministic choice 
inside of a search script. (See the "choice" statement.) This enables 
you to solve only one problem instead of the 2^n (in fact, you still 
solve 2^n problems, but you can express it using a single script).

Hope this helps,
Filip

> Thanks for the ideas.  I did know about these possibilities.  What I am 
> having trouble with is actually implementing them.
> Could you give me a small example of each?  I would really, really, 
> appreciate it.
> 
> 
> Hi,
> 
> generally, you have 2 possibilities.
> 
> The first is to constrain the task start so that the task can not 
> intersect the interval (e.g. using the \=: operator). You know the task 
> length, so no problem here.
> 
> The other option is even easier: create an artificial fixed task that 
> occupies the resource during the outage.
> 
> Cheers,
> Filip
> 
>> / Hi All,
> />/ />/ I have been studying very hard and have finally created an 
> application />/ that will schedule tasks in oz.  What is confusing me is 
> how to do the />/ following:
> />/ />/ 1.  Don't schedule tasks for a certain time frame on a 
> particular />/ resource (Either because the resource is down for 
> repairs/unavailable or />/ because a task has already been started and 
> needs to finish)
> />/ />/ The lines that deal with this in my code are:
> />/ />/ fun {Compile Problem}
> />/     TaskSpec = Problem.tasks
> />/     Dur = {GetDur TaskSpec}
> />/     TestVal =  10
> />/     TestVal2 = 15
> />/   in
> />/     proc {$ Start}
> />/     Start={GetStart TaskSpec}
> />/     {ForAll TaskSpec
> />/     proc {$ T}
> />/        {ForAll {CondSelect T pre nil}
> />/        proc {$ P}
> />/          Start.P + Dur.P =<: Start.{Label T}
> />/          TestVal =<: Start.{Label T}
> />/          TestVal =<: Start.P
> />/ %%          Start.P + Dur.P =<: TestVal2
> />/ %%          Start.P \=: TestVal
> />/ %%          Start.P \=: TestVal2
> />/        end}
> />/     end}
> />/ {Record.forAll Start proc {$ S}
> />/                         S={FD.reflect.min S}
> />/                          end}
> />/     end
> />/ />/   end
> />/ />/ I can get it to start from a certain point or not schedule after 
> a />/ certain point, but I can't figure out how to make the constraints 
> such />/ that tasks will be scheduled before a reserved time frame and 
> after.  />/ Any ideas/help would be greatly appreciated.  By the way I 
> am very />/ impressed with mozart oz.  I am somewhat of a newbie to 
> constraint />/ programming but this made it easy to begin./
> 
>