Originally posted by: Puppy26

Hi all,

Could someone help me for the below query.

Actually, I got two equations. say for an example,

a= 5, b = 5, c=6, d= 4;

x = a+b;

y = c+d;

Z = x/y;

I tried to using this technique in opl cplex but I'm getting an error as "OPL cannot extract the expression" but if i give it as x - y, I'm getting the result.

how do I get the results now!!

Many thanks!

 

regards,

puppy

 

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi,

 

can you post the OPL model you wrote ?

 

regards

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Puppy26

Hi Alex,

Here is the code

 

 forall ( y in Years)

          Streetturnvalue:

  StreetTurnPct[y] == sum (c in Consignees, s in Shippers) SCSupply[s][c][y]/Demand[y];

  

 

In the place of Demand in StreetTurnPct[y], it has to be Demand[y] - ShipperRejects [y].. Since the Demand[y] and ShipperRejects[y] both are variable, im getting error as "OPL cannot extract the expression".

Many thanks!

 

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi,

let's try to fix

forall ( y in Years)

          Streetturnvalue:

  StreetTurnPct[y] == sum (c in Consignees, s in Shippers) SCSupply[s][c][y]/Demand[y];

This is not allowed because of / which is not linear.

But why do not you write

forall ( y in Years)

          Streetturnvalue:

  0<=sum (c in Consignees, s in Shippers) SCSupply[s][c][y]<=0.2*Demand[y];

?

 

regards

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Puppy26

Hi,

As I have already mentioned, in the place of Demand[y], it has to be Demand [y] - ShipperRejects[y].... if I give 

 

forall ( y in Years)

          Streetturnvalue:

  0<=sum (c in Consignees, s in Shippers) SCSupply[s][c][y]<=0.2*(Demand[y] - ShipperRejects[y]);

 

I'm getting error as ShipperRejects[y] not allowed..

May I know how can I solve this now!!

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi

 

can you attach your .mod and .dat ?

 

Regards

#DecisionOptimization
#OPLusingCPLEXOptimizer

PS:

Have you declared ShipperRejects[y] ?

 

regards

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Cplexbeginner

Hi,

 

I have the same problem. 

After writing a long code, I reached to the error you mentioned. It seems that "/" is not a good syntax. 

I was wondering if somebody can help.

 

Bests,

Beginner,

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi

can you post your complete model and data ?

regards

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Cplexbeginner

Hello,

 

I have attached the files.

I could handle one constraint, with multiplying both side of the equality by the denominator. However, I could not do the same for the other constraint. The reason is that it has fractional power.

 

Best Regards, 

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi

your problem does not seem to be linear. You should have a look at what CPLEX can solve in the documentation, or linearize your model or try with CPO.

In order to try with CPO, simply use :

using CP;

and then do some variable change in order to turn dvar float into dvar int

Could that help ?

regards

 

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Cplexbeginner

Hi,

I have done your suggestion. 

There is no compiling error but it makes the problem infeasible.

My variable are all float, but when I put them int, the problem becomes infeasible.

 

What can I do to handle it?

Bests,

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi

the attached model works

I let you uncomment more constraint by constraint in order to spot what the issue is with your model

regards

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Cplexbeginner

Hi,

I really appreciate your help.

 

I get this error after running the attached file.

 

What is it? and How can I handle it?

 

Bests,

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi

if you kept

using CP;
 

you should not have that error

regards

#DecisionOptimization
#OPLusingCPLEXOptimizer

Originally posted by: Cplexbeginner

Hi,

 

That is great. However, the decision variables are integer. When I uncomment some constraints, the problem becomes infeasible due to int variables.

 

Can I introduce float for CP?

 

Best, 

#DecisionOptimization
#OPLusingCPLEXOptimizer

Hi

can you have a look at the example

examples/opl/floatexpr

?

regards

 

#DecisionOptimization
#OPLusingCPLEXOptimizer