Decision Optimization

i used the code of user Marko Reclic to create a deep copy of an IloModel.

IloEnv testenv;IloModel testmodel(testenv);IloCplex testcplex(testmodel);IloNumVarArray x = CreateNumVarArray(testenv, 2, "x", 0, 1);IloObjective testobj = IloMaximize(testenv, IloSum(x));testmodel.add(testobj);IloRangeArray cnstr = CreateRangeArray(testenv, 3, "c");for (int i = 0; i < cnstr.getSize(); i++) {    cnstr[i].setLinearCoef(x[0], (3 - i) + 2);    cnstr[i].setLinearCoef(x[1], i * 3 + 1);    cnstr[i].setUB(10 * (5 - i) - 2);}testmodel.add(cnstr);IloModel testmodel1(testenv);for (IloModel::Iterator it(testmodel); it.ok(); ++it)    testmodel1.add(*it);

My question is how to add new columns to testmodel1. For testmodel i would use the following code. I don't know what to apply for testmodel1.

IloNumColumn col(testenv);col += testobj(22);for (int i = 0; i < cnstr.getSize(); ++i) {    col += cnstr[i](i * 3 + 5);}x.add(IloNumVar(col, 0, 1, ILOFLOAT));

Dear Ozan,

My understanding of your code is that by iterating over the `testmodel` entities, you are creating a shallow copy of the model (not a deep copy). This means that both models are then updated when a new column is added.

Anyway, trying to clone and edit a model can be confusing and lead to unnecessary complications. I would rather advice to wrap the creation of your model in a function, and then invoking this function a second time to create a new instance of the model.

Best regards,

i used the code of user Marko Reclic to create a deep copy of an IloModel.

IloEnv testenv;IloModel testmodel(testenv);IloCplex testcplex(testmodel);IloNumVarArray x = CreateNumVarArray(testenv, 2, "x", 0, 1);IloObjective testobj = IloMaximize(testenv, IloSum(x));testmodel.add(testobj);IloRangeArray cnstr = CreateRangeArray(testenv, 3, "c");for (int i = 0; i < cnstr.getSize(); i++) {    cnstr[i].setLinearCoef(x[0], (3 - i) + 2);    cnstr[i].setLinearCoef(x[1], i * 3 + 1);    cnstr[i].setUB(10 * (5 - i) - 2);}testmodel.add(cnstr);IloModel testmodel1(testenv);for (IloModel::Iterator it(testmodel); it.ok(); ++it)    testmodel1.add(*it);

My question is how to add new columns to testmodel1. For testmodel i would use the following code. I don't know what to apply for testmodel1.

IloNumColumn col(testenv);col += testobj(22);for (int i = 0; i < cnstr.getSize(); ++i) {    col += cnstr[i](i * 3 + 5);}x.add(IloNumVar(col, 0, 1, ILOFLOAT));

Dear Hugues

Thank you for your reply. I think i am creating a deep model because adding new constraints to the copy does not affect the original model:

IloRangeArray cnstr1 = CreateRangeArray; testmodel1.add(cnstr1);

However adding columns only to testmodel1 is not possible:

IloNumColumn col(testenv);col += testobj(int);for (int i = 0; i < cnstr.getSize(); ++i) {    col += cnstr[i](int);}IloNumVar newVar(col, 0, 1, ILOFLOAT);testmodel1.add(newVar);

This is probably because I don't have copies of IloObjective and IloRangeArray. How can i create those copies? Or in general how can i add new columns to testmodel1 without modifying testmodel?

Dear Ozan,

My understanding of your code is that by iterating over the `testmodel` entities, you are creating a shallow copy of the model (not a deep copy). This means that both models are then updated when a new column is added.

Anyway, trying to clone and edit a model can be confusing and lead to unnecessary complications. I would rather advice to wrap the creation of your model in a function, and then invoking this function a second time to create a new instance of the model.

Best regards,

i used the code of user Marko Reclic to create a deep copy of an IloModel.

IloEnv testenv;IloModel testmodel(testenv);IloCplex testcplex(testmodel);IloNumVarArray x = CreateNumVarArray(testenv, 2, "x", 0, 1);IloObjective testobj = IloMaximize(testenv, IloSum(x));testmodel.add(testobj);IloRangeArray cnstr = CreateRangeArray(testenv, 3, "c");for (int i = 0; i < cnstr.getSize(); i++) {    cnstr[i].setLinearCoef(x[0], (3 - i) + 2);    cnstr[i].setLinearCoef(x[1], i * 3 + 1);    cnstr[i].setUB(10 * (5 - i) - 2);}testmodel.add(cnstr);IloModel testmodel1(testenv);for (IloModel::Iterator it(testmodel); it.ok(); ++it)    testmodel1.add(*it);

My question is how to add new columns to testmodel1. For testmodel i would use the following code. I don't know what to apply for testmodel1.

IloNumColumn col(testenv);col += testobj(22);for (int i = 0; i < cnstr.getSize(); ++i) {    col += cnstr[i](i * 3 + 5);}x.add(IloNumVar(col, 0, 1, ILOFLOAT));

Dear Ozan,

I'm still confused about the "deep copy" snippet...
I did a simple experiment where I edited "cnstr" in "testmodel" (duplicating the same loop, but using different values for the coefs) AFTER "testmodel1" has been created using the iterator over IloModel entities.
Then, I displayed both models as follows:

        IloModel testmodel1(testenv);        for (IloModel::Iterator it(testmodel); it.ok(); ++it) {            testmodel1.add(*it);        }        testenv.out() << "=========================================" << std::endl;        for (int i = 0; i < cnstr.getSize(); i++) {            cnstr[i].setLinearCoef(x[0], (6 - i) + 2);  // Arbitrary updates to original constraints...            cnstr[i].setLinearCoef(x[1], i * 11 + 1);            cnstr[i].setUB(10 * (49 - i) - 2);        }        testenv.out() << "=========================================" << std::endl;        for (IloModel::Iterator it(testmodel); it.ok(); ++it) {            IloExtractable e = *it;            testenv.out() << "TestModel : " << e << std::endl;        }        for (IloModel::Iterator it(testmodel1); it.ok(); ++it) {            IloExtractable e = *it;            testenv.out() << "TestModel1 : " << e << std::endl;        }

The same information is displayed for both models, meaning that a shallow copy was performed, not a deep copy.

Could you replicate the experiment on your side ?

Is performing a deep copy of the model the only possibility in your application ? Wouldn't it be better to just recreate a new model from scratch for testmodel1 ?

Best regards,

Dear Hugues

Thank you for your reply. I think i am creating a deep model because adding new constraints to the copy does not affect the original model:

IloRangeArray cnstr1 = CreateRangeArray; testmodel1.add(cnstr1);

However adding columns only to testmodel1 is not possible:

IloNumColumn col(testenv);col += testobj(int);for (int i = 0; i < cnstr.getSize(); ++i) {    col += cnstr[i](int);}IloNumVar newVar(col, 0, 1, ILOFLOAT);testmodel1.add(newVar);

This is probably because I don't have copies of IloObjective and IloRangeArray. How can i create those copies? Or in general how can i add new columns to testmodel1 without modifying testmodel?

Dear Ozan,

My understanding of your code is that by iterating over the `testmodel` entities, you are creating a shallow copy of the model (not a deep copy). This means that both models are then updated when a new column is added.

Anyway, trying to clone and edit a model can be confusing and lead to unnecessary complications. I would rather advice to wrap the creation of your model in a function, and then invoking this function a second time to create a new instance of the model.

Best regards,

i used the code of user Marko Reclic to create a deep copy of an IloModel.

IloEnv testenv;IloModel testmodel(testenv);IloCplex testcplex(testmodel);IloNumVarArray x = CreateNumVarArray(testenv, 2, "x", 0, 1);IloObjective testobj = IloMaximize(testenv, IloSum(x));testmodel.add(testobj);IloRangeArray cnstr = CreateRangeArray(testenv, 3, "c");for (int i = 0; i < cnstr.getSize(); i++) {    cnstr[i].setLinearCoef(x[0], (3 - i) + 2);    cnstr[i].setLinearCoef(x[1], i * 3 + 1);    cnstr[i].setUB(10 * (5 - i) - 2);}testmodel.add(cnstr);IloModel testmodel1(testenv);for (IloModel::Iterator it(testmodel); it.ok(); ++it)    testmodel1.add(*it);

My question is how to add new columns to testmodel1. For testmodel i would use the following code. I don't know what to apply for testmodel1.

IloNumColumn col(testenv);col += testobj(22);for (int i = 0; i < cnstr.getSize(); ++i) {    col += cnstr[i](i * 3 + 5);}x.add(IloNumVar(col, 0, 1, ILOFLOAT));