random seed explanation

[Željko Vrabec]

Hi guys!

I'm trying to figure out how random seed generator works and can I change it to improve generation time.

Does anyone have some time and will to explain?

Thanks in advance!

[Liviu Lalescu]

Hello, Zeljko,

I could try (not sure if I'll go to sleep soon, but if so, I will answer tomorrow).

RNG (random number generator) -> it simply provides random numbers for FET, so that FET generates different timetables each time, and in each timetable the slots are chosen semi-randomly (from the best slots, FET chooses one).

You cannot guess a good/favorable RNG seed for your file. Generally, the random seed must remain random.

I found a way to use random seed setting for a very difficult file: I generated with a few minutes (5-20 - I am not sure) time limit on multiple threads, and say there were placed 98/100, 95/100, 99/100, and 97/100. I took the random seed for the best (99/100), and put it in FET, and started a single generation with that seed, without a time limit, and I got a timetable after a few hours. Or something like that.

[Željko Vrabec]

Thanks a lot!

[Liviu Lalescu]

You're welcome!

Another use of the seed of the RNG is to check that the computation is the same (if the after and before seeds are the same). This can be done to check that the algorithm is the same, to compare the speed of different computers/operating systems, to ensure that you get the same time in a demonstration, etc.