<DIV><DIV>Hello GATE?ers,<o:p></O:P> I?m looking for some help with locking the random seed. We are simulating a system with two different kinds of detectors (one hi-res and one medium resolution), and we therefore have to simulate each simulation setup twice: one time with detector A attached as sensitive detector (SD), and the second time with detector B attached as SD (since the attachment tree is of single branch). During these simulations, the non-attached system is attached as<st1:place><st1:city> Phantom</ST1:CITY> <st1:state> SD.</ST1:STATE> </ST1:PLACE> These two simulations are then together sorted to get the coincidences. To be able to do this however we need to lock the random seed. We have tried to lock it with the following line:<o:p></O:P>/random/resetEngineFrom my_rndm_file.rndm<o:p></O:P>Even though the results are identical each time we run a simulation with detector A (or B), we get a different simulation when switching to detector B (or A). (The number of events simulated are different in the two runs, and the coincidences are randoms.) Any help on this matter, how to lock the random seed, is appreciated. Or is it that changing the attachment and SD, changes the simulation? How do we in that case simulate our system?<o:p></O:P>Martin Janecek</DIV></DIV>