Amin Ahmadi

I understood. Your suggestions work perfectly.  Thanks for your time. 

Eli, Thanks for your response. As I said, I am using the remove function to eliminate constraints. Since I have to remove more than 6000 thousand constraints, this does not work for me. This is the...

Thanks for your explanation. I have a general question. In my case, building the lp model is taking too much time ( more than 3000 seconds). I am seeking a way to generate the model in a short time...