Originally posted by: SystemAdmin

[stopro said:]

Hello everyone,

I am running CPLEX locally on a windows machine and a server, the CPLEX license is on the server . My windows machine is quite powerful; when I run a large MIP on the both the server and my windows box, CPLEX on my machine finishes at least 10-15 minutes ahead of the server.

But now I am running an iterative AMPL code, that solves subproblems, again on both the server and my box. The run on the server now finishes in 3-5 minutes, while my windows box takes 25 - 30 minutes to finish. 

It seems as though there is some latency in fetching the license from the server to my windows box, and it is getting magnified due to multiple iterations. Is this expected behavior? Does anyone know a way of getting around this?
Thanks in advance!


#CPLEXOptimizers
#DecisionOptimization

Originally posted by: SystemAdmin

[achterberg said:]

Such a large time difference can only be attributed to the license manager if you are solving a LOT of sub-problems. I don't know what AMPL does, but if it solves thousands of very small problems, it could be that the license manager is the bottleneck.

Are the two runs taking the same solving path (same total number of sub-problem solves, total number of branching nodes, total number of simplex iterations)?

Do you see a large discrepancy between CPU and wall-clock time? You could set the "clocktype" parameter to CPU time and wall-clock time explicitly, and set the "threads" parameter to 1 (otherwise, CPU time does not make much sense). Then compare the two timings reported by CPLEX (if this is possible within the AMPL environment). If the wall-clock time is much larger than the CPU time, this points to some idle waiting, which is most probably in the license check.

#CPLEXOptimizers
#DecisionOptimization