I have tried to change some constraints in my code but when the number of requests in data is lower than 18, the cplex function normally as I increase the number of request to 19 and above the cplex takes a long time and sometimes end up with out of memory problem. Also if i change the destination and source in the requests tuple or if I change the parameter "t" , the cplex take much more time even if i keep the same number of requests. for instance , for 20 requests, for the initial data it take 16 min to give output however for 20 requests and different duration (t) or source or destination in tuple it will take 2,3 or more hours or even out of memory case.
So please can somebody tell me why this is happening and how can I solve it.
I will upload the .dat . mod file
Is there any problem in the way I wrote the codes attached in the post?