Originally posted by: Julia189

 

Hi everyone!

We are trying to implement these constraints (see attached) into CPLEX but once we run the model, the following error pops up:

"CPLEX (default) cannot extract expression:…"

 

This is the code referring to 17.1 and 17.2:         

forall(i in I, t in T) ct17[i][t]:

ivp[i][t] <=ivp[i][t-1] + sum (c in C) prp[c][i][t] - sum (s in S)  tp[s][i][t];

 

forall(i in I, t in T:t>=pp[i]) ct171[i][t]:

ivp[i][t] >=ivp[i][t-1] + sum (c in C) prp[c][i][t] - sum (s in S) tp[s][i][t] - (ivp[i][t-pp[i]] - sum (s in S, x in t-pp[i]+1..t)tp[s][i][x]);

 

This code is referring to 18.1 and 18.2:

forall(j in J, s in Sj[j], p in Pj[j], t in T) ct18[j][s][p][t]:

ivs[s][p][t] <=ivs[s][p][t-1] + prs[s][p][t] - sum (m in Mj[j]) ts[s][p][m][t];

 

forall(j in J, s in Sj[j], p in Pj[j], t in T: t>= ps[p]) ct181[j][s][p][t]:

ivs[s][p][t] >=ivs[s][p][t-1] + prs[s][p][t] - sum (m in Mj[j]) ts[s][p][m][t] -(ivs[s][p][t-ps[p]] - sum (m in Mj[j], y in t-ps[p]+1..t)ts[s][p][m][y]);

We think the problem could be x and respectively y which are auxiliary variables. In case of the 17.2 constraint we need two sums, one summing up over s and one summing up over x. X should have the range from t-pp[i]+1 up to t. We don't have a set for x since it is only an auxiliary variable for this constraint. x should be part of the set T. t is part of the set T and acts as upper bound for our sum. We are not sure if this is correct and if we implemented it correctly.

Does anyone know how to solve this ?

Thanks in advance!

Best,

Julia

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#OPLusingCPLEXOptimizer

Hi,

can you try to remove the labels such as:

ct18[j][s][p][t]:

?

regards

https://www.linkedin.com/pulse/ist-mathematische-optimierung-und-wie-kann-sie-helfen-alex-fleischer/

 

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Julia189

Hi Alex,

 

we just removed the ct labels and have less erros now. Thanks!  

Still we suppose there is a problem in this section: 

sum (s in S, x in t-pp[i]+1..t)tp[s][i][x]);

Can you tell us whether this is the corret way to implement this range of the sum? Meaning that x is part of the set T and should refer to t (which is also of big T) for the upper and lower bound of the sum. 

 

 

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi,

Maybe you could attach .mod and .dat so that other users  could try.

regards

https://www.linkedin.com/pulse/which-aml-gpl-do-you-use-call-cplex-alex-fleischer/

#DecisionOptimization
#OPLusingCPLEXOptimizer