Originally posted by: Broncho

Dear all,

In my codes, Matrix is an int type matrix. P is a variable array. I would like to give constraints for my LP problem. So, I define an IloExprArray to record the sum of Matrix*P for each row. But when I run the codes, it is blocked at the line of temp[j]+=Matrix[j][i]*P[i];. I also try to print  "temp", nothing can be printed. No problems can be found in Matrix and P because I can print them. I think I may not use IloExprArray correctly. But when I read the references, it looks OK. I don't know the reason why "temp" cannot work. Please help me. Thanks!

I think you missed this detail in the reference documentation of IloExprArray(IloEnv, IloInt):

This constructor creates an array of n elements. Initially, the n elements are empty handles.

So you should do

temp[j] = IloExpr(env);

before you access temp[j] for the first time.

Originally posted by: Broncho

Thanks! It works!