Originally posted by: kutikz

hi..
please help me to solve this problem. im a beginner user for CPLEX, and i wanna use CPLEX to solve MIP problem but i found so many errors which said that "CPLEX cannot extract expression"

for example:
CPLEX(default) cannot extract expression: c16: forall(t in 1..10) sum(i in 1..12) w(i)(t) <= inventP(t+(-1)).

for

c16=forall(t in period) sum(i in customer)w[i][t]<=inventPt-1;
where
period=1..10;
customer=1..12;
dvar int Pperiod;
dvar int wcustomerperiod;
thanks in advance
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Originally posted by: SystemAdmin

Hi,

I'm not sure, as the code is not properly formatted and I coud not find the declaration for

inventP[]

but my guess is that for t=1 you access inventP[0], which is not defined.

Hope this wil be of any help.

Regards
Norbert
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Originally posted by: kutikz

sorry, what i meant was inventPperiod

if i assume that inventP[0]=0, should i change the range of the period?or how should i manage this problem?

many thanks
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Originally posted by: SystemAdmin

What you should do is define a range 0..10 and index inventP[] over this range.
What is inventP[]? A data element or a decision variable. Dependent on this
answer you will have to initialize/fix the value of inventP[0] to zero.

Regards
Norbert
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Originally posted by: kutikz

inventP[] is a decision variable, but for period 0 or inventP[0] the value will be set to 0.
im not sure about how to set it.
and, is it possible if i make two different ranges for the period ? because in other constraints im only using period 1 until 14

thanks
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Originally posted by: SystemAdmin

You can define as many ranges as you like

range Periods0 = 0..10;
range Periods1 = 1..10;
range Periods2 = 1..14;
 
dvar int x[Periods0];
dvar int y[Periods1];
dvar int z[Periods2];

(and so so ...) What you cannot do is define one set over two ranges ;-) ...

The easiest way to fix inventP[0] to 0 is to add a constraint

inventP[0] == 0;

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Originally posted by: kutikz

thank you :D
this is really helpful
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Originally posted by: kutikz

i have tried the code as u suggested but im still finding errors, may u help me to trace the causes?
i attached my model, please take a look at them. really need ur help

thank you
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Originally posted by: kutikz

need some help more because i still find error in my model
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Hi

you made an error with the index.

In the objective

sum(i in customer, t in period1)(((2*dist[0][i])/dem[i][t])*w[i][t])

t is in period1 ie 0 .. T-1 whereas dem is defined on period ie 1 .. T

Instead of

sum(i in customer, t in period1)

maybe you should write

sum(i in customer, t in period)

Regards

Alex
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Originally posted by: telangana

Hi Alex,

 I am attaching my mod as well as dat file of my model

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Hi,

sometimes it s better to create a new thread rather than use an old thread in the forum.

Can you attach your xls file too ?

regards

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Originally posted by: telangana

Hi,

Iam attaching my xls file .Please find the attachment

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Hi,

simply an out of bound.

minimize  sum(t in 1..5) (p*X[t]+k*H[t]+l*F[t]+r*W[t]+e*I[t]);
  //constraints
  subject to
  {
  forall(t in weeks:(t-1) in weeks )
   conso1:
    W[t]== W[t+(-1)]+H[t]-F[t];
    
    forall(t in weeks:(t-1) in weeks)
     conso2:
    I[t]==I[t-1]+X[t]-demand[t];
     
     W0==5;
     I0==20;
    
      
  }
 

will work fine.

 

I changed 

forall(t in weeks)

into

forall(t in weeks:(t-1) in weeks)

regards

 

PS:

Do not hesitate to retweet

https://twitter.com/AlexFleischer1/status/773415864959991808

 

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Originally posted by: telangana

Hi,

Thank you for helping me its working and one more problem is i am facing problem in attaching access file .

 

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Hi,

are you a researcher ?

{string} cargos={"A","B"};
{string} compartment={"1","2"};
tuple cargotype{
float available_weight;
float volume_per_ton;
float profit_per_ton;
}
tuple compatype {
float weightcapacity;
float spacecapacity;
}
cargotype cargodata [i in cargos]=<1,2.0,3.0>;
compatype compadata [i in compartment]=<1.0,2.0>;

//variables
dvar float+ x[cargos][compartment];
dvar float+ y;

dexpr float profit = sum (i in cargos,j in compartment)cargodata[i].profit_per_ton*x [i][j];

dexpr float SpaceUsedPerComp[j in compartment] = sum (i in cargos) cargodata[i].volume_per_ton * x[i][j];
dexpr float weightusedpercomp[j in compartment]= sum(i in cargos)x[i][j];

maximize profit;
subject to
{
SpaceUsedPerComp["1"]==0;
weightusedpercomp["1"]==0;
}

works fine.

What is the error you get ?

regards

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Originally posted by: telangana

Hi,

Yes I am a research assistant in my university.

dexpr float SpaceUsedPerComp[j in compartment] = sum (i in cargos) cargodata[i].volume_per_ton * x[i][j];

at this line i am getting error and it is  variable indexer size is not allowed for generic array.

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Hi,

ok, can you try to comment that so that it works and

then do oplrun -de in order to export .dat and

then share that .dat here ?

regards

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