Originally posted by: MchelLeo

Hi Alex,

I have a constraint, using Big_M. But I don't know why profits_value and Q[i] values are No value?. Please help me.

.............mod...............

{string} n = ...;
float bubget=5;

tuple profit{
float cost;
float quantity;
float availability;
float null;
}
float M = 99999999;

profit profits [n] = ...;

dvar float+ Q[n];
dvar boolean X[n];
dexpr float profits_value = sum (i in n) X[i] * Q[i];

maximize profits_value;

subject to {
forall (i in n){
Q[i] <= M * X[i];
}

forall (i in n){
Q[i] <= profits[i].availability;

}

forall (i in n){
sum (i in n) Q[i] * X[i]<=bubget;
}
}

........dat...........

n = {n1,n2,n3,n4};

profits = [<1, 2, 2, 0>

              <3, 1, 3, 0>

              <5, 2, 5, 0>

              <8, 1, 6, 0>];

Thanks,

Leo

Originally posted by: MchelLeo

Hi Alex,

Please help me in advance.

Thank you,

Leo

Hi

your problem is not PSD (not positive semi-definite)

see

https://twitter.com/AlexFleischer1/status/843806521918132225

you could rewrite your .mod into

{string} n = ...;
float bubget=5;

tuple profit{
float cost;
float quantity;
float availability;
float null;
}
float M = 99999999;

profit profits [n] = ...;

dvar float+ Q[n];
dvar boolean X[n];
dvar float QX[n];

dexpr float profits_value = sum (i in n)  QX[i];

maximize profits_value;

subject to {
forall (i in n){
Q[i] <= M * X[i];

forall(i in n) (X[i]==1) => (QX[i]==Q[i]);
forall(i in n) (X[i]==0) => (QX[i]==0);

}

forall (i in n){
Q[i] <= profits[i].availability;

}

forall (i in n){
sum (i in n) QX[i]<=bubget;
}
}

regards

Originally posted by: MchelLeo

Hi Alex,

I edited the constraint as follows:

Why Q3=0, Q4=0 while X3=1, X4=1?. I want, if X=0 then Q=0. Please help me.

................mod....................

{string} n = ...;
float bubget =10;

tuple profit{
float cost;
float quantity;
float availability;
float null;
} 
float M = 99999999;

profit profits [n] = ...;

dvar float+ Q[n];
dvar boolean X[n];
dexpr float profits_value = sum (i in n) Q[i];

maximize profits_value;

subject to {
forall (i in n){
Q[i] <= M * X[i];
}

forall (i in n){
Q[i] <= profits[i].availability;
} 
forall (i in n){
sum (i in n) Q[i] * 2 <=bubget;
}
} 

...........................dat.......................................

n = {n1,n2,n3,n4};
 profits = [<1, 2, 2, 0>
                <3, 1, 3, 0>
                <5, 2, 5, 0>
                <8, 1, 6, 0>]; 

Thanks,

Van Can

Hi,

you have

, if X=0 then Q=0.

since in your solution X is always 1

regards

PS:

If you add

assert forall(i in n) (X[i]==0) => (Q[i]==0);

after your model you do not get any error

Originally posted by: MchelLeo

Dear Alex,

I would like to use from Java to make this condition in OPL: (Q[i]==0) => (X[i]==0). Then, how to write?

Thanks,

Leo

Hi,

if you want to rewrite that in java then you should use

public final IloConstraint ifThen(IloConstraint con1, IloConstraint con2) throws IloException

regards

Originally posted by: MchelLeo

Hi Alex,

Thank you so much for the suggestions.

Leo