# Decision Optimization

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## help with advanced scheduling problem

• #### 1.  help with advanced scheduling problem

Posted 5 days ago

Hello,

I'm working on a gym equipment optimization algorithm. Part of the goal is to help gyms stay safe during COVID times (scheduled cleaning).  I am new to OPL and CPLEX,  and based on the examples I've seen in the CPLEX libraries, this problem seems to be intermediate to advanced level. I have gotten to a certain point and I'm now stuck. I don't necessarily want to just post all of my code on here but I would be so grateful if someone who has done some advanced job shop/ scheduling problems would reach out to me, if you are interested in helping me out!

Thanks,
Christie

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Christie Entwistle
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• #### 2.  RE: help with advanced scheduling problem

Posted 2 days ago
You should really provide more details so that we can get an idea about what exactly is blocking you right now. Otherwise it is hard to tell who is the right person to help you.

In case you cannot upload your issues here, you can contact me at daniel(dot)junglas(at)de(dot)ibm(dot)com.

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Daniel Junglas
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• #### 3.  RE: help with advanced scheduling problem

Posted yesterday
I had a chat with Christie. FWIW, she's using OPL to build a scheduling model and CP Optimizer to solve it.

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Paul Rubin
Professor Emeritus
Michigan State University
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• #### 4.  RE: help with advanced scheduling problem

Posted 16 hours ago
Scheduling tutorial is very pedagogic and gives a quite wide view on the scheduling concepts through a set of variants around building a house
• using cumulative functions (pulse, heightAtStart...) that model cumulative resources or reservoirs (see the cash example)
• using unary resource with setup times (noOverlap on sequence)
• using calendar to model breaks (intensity / forbid)
• using state functions, for instance  : you cannot start electricity if the house is in state 'dirty'
• optional intervals to model alternative
Did you have a look at all this tutorial and get a sound understanding ? These constructs are quite powerful and allow to build from simple to complex models. Though, they are typical pitfalls that people are likely to do when they are new to (and sometimes even experienced with)  CP for scheduling. For instance, modeling some constraints with discretizing the time is absolutely a wrong idea (I did it some times ago :-)

Can you elaborate a little bit more on the point where you are stuck ?

David Gravot
DecisionBrain
david(dot)gravot(at)decisionbrain(dot)com

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David Gravot
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• #### 5.  RE: help with advanced scheduling problem

Posted 11 hours ago
Thanks everyone.

I had a chance to talk with Paul Rubin yesterday and he explained to me the difference between CPLEX and CPOptimizer :). So yes, I am using CPOptimizer for a scheduling problem written directly in OPL using ILOG CPLEX Optimization Studio.

I have looked at the scheduling tutorial and imported many examples. I am now familiar with using interval variables, sequences of intervals, noOverlap, alternative functions, and a few other things. My current solution is pretty closely modeled after the built-in example sched_tasks.mod and dat. Substitute out the "resources" for "gym equipment" and operations for exercises, and you have the foundation of my current model.

Here is something I am currently struggling with:
I want to create an interval variable for the consumption of plates (to put on barbells). Lets say my  small gym has 5 sets of 10 lb plates, and 2 sets of 25. Unlike the mandatory resources (equipment) that I already have coded, plates can be used in any combination to add up to a certain weight as long as the bar is balanced. The weight cannot go over a certain amount depending on the client's ability. The objective function should try to push the weight as high as it can go without going over for that person (e.g. "Bill" has a 1RM of 100). I also have to consider the weight of a 45 lb barbell.  Currently I have an objective expression which I'm maximizing called "totalvolume" which multiples the reps times the weight of the resource being used and sums over the client's total workout interval.  How can I deal with a resource that can be used in multiple combinations like this? I hope the answer is not that I would have to spell out each possible combination/allocation of plates...

Thanks,
Christie