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| Rules query 01/07/2017 at 17:11 #96098 | |
Lyn-Greenwood
240 posts |
What's the difference between the Alternatives Rule and the Mutually Exclusive Rule? My understanding is that if two trains are Alternatives, then just before the earlier of the two is due to enter a simulation, a random choice is made as to which one should run. However, if two trains are Mutually Exclusive, I believe the earlier of the two trains will always run unless another Rule (or condition) prevents it. Is this how the two Rules work? I'd be very grateful if someone could clarify the difference between the two Rules.
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| Rules query 01/07/2017 at 22:52 #96099 | |
GW43125
495 posts |
Lyn-Greenwood in post 96098 said:What's the difference between the Alternatives Rule and the Mutually Exclusive Rule? My understanding is that if two trains are Alternatives, then just before the earlier of the two is due to enter a simulation, a random choice is made as to which one should run. However, if two trains are Mutually Exclusive, I believe the earlier of the two trains will always run unless another Rule (or condition) prevents it. Is this how the two Rules work? I'd be very grateful if someone could clarify the difference between the two Rules.As I understand it, "are alternatives" means either one or the other will occur, whereas mutually exclusive (in a mathematical sense at least) just means two events cannot occur at the same time. So with mutually exclusive selected, both should still be able to enter, just one after the other. Hope this helps. Log in to reply |
| Rules query 01/07/2017 at 23:54 #96100 | |
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clive
2789 posts |
Lyn-Greenwood in post 96098 said:What's the difference between the Alternatives Rule and the Mutually Exclusive Rule? My understanding is that if two trains are Alternatives, then just before the earlier of the two is due to enter a simulation, a random choice is made as to which one should run.Not quite. Whenever a train is about to enter, then all "Alternatives" rules are checked and those that match that train are noted. A list is then built up of all trains that match any of those rules that haven't already been cancelled. Finally, one such train is selected and all others cancelled. If that's the train that we started with, it enters. Otherwise the selected train will eventually enter (unless something else prevents it). This check is done after most other rules to prevent all the options getting cancelled. If a train enters from a chained sim, the "Alternatives" rules that match it are checked and all other trains that match are cancelled. Lyn-Greenwood in post 96098 said: Not quite. When the user is about to discover that a train is entering (which could be when it enters, when the user is warned that the train is delayed, or when the user is phoned about the train), all Mutually Exclusive rules that match that train are flagged as "achieved" and all other trains that match those rules are cancelled. So it might not be the earliest train but you've got the idea. (The whole thing is historical: Mutually Exclusive is somewhat older than Alternatives, which were added because people couldn't figure out how to do some of the things they wanted.) Log in to reply The following user said thank you: BarryM |
| Rules query 02/07/2017 at 13:22 #96102 | |
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Lyn-Greenwood
240 posts |
Thanks for the detailed explanation, Clive. I've now got a much better understanding of how the two rules work. I've noticed that some user-contributed timetables are using the Mutually Exclusive rule when they should really be using the Alternatives rule, so I'll raise this with the relevant authors. Log in to reply |