Is this supposed to happen? - Accuracy of the sim or my problem?

[Hegemon54]

So for example when I start up the Jupiter and its Moons simulation, I have it set to Accurate Mode and still within 60 years all the moons of Jupiter have been slingshot into random directions.  I'm guessing thats not supposed to happen?  Are my settings wrong or is the sim just not accurate?

[Vohn_exel]

Haha I get the same problem when I run our solar system. If you leave it on after a while, Mars will shoot off on it's own about sixty years into the future This problem has prevented me from creating my own solar system as everything flies away from the moon save for one or two planets.

[ChemicalBR0]

as you increase the time-step it gets less accurate.
the slower you have the sim running the more accurate it will be.

if you ran it in realtime for 60 years the planets wouldn't slingshot.

you just have to find the happy medium

[Dan Dixon]

So for example when I start up the Jupiter and its Moons simulation, I have it set to Accurate Mode and still within 60 years all the moons of Jupiter have been slingshot into random directions.  I'm guessing thats not supposed to happen?  Are my settings wrong or is the sim just not accurate?

So you open up... Jupiter and its Moons
Switch to Accurate mode (RK4)

And it breaks?
Are you changing the time step at all?

I found that the simulation is more accurate when the program is focused.

Hmm... that shouldn't have any effect.

[Hegemon54]

So for example when I start up the Jupiter and its Moons simulation, I have it set to Accurate Mode and still within 60 years all the moons of Jupiter have been slingshot into random directions.  I'm guessing thats not supposed to happen?  Are my settings wrong or is the sim just not accurate?

So you open up... Jupiter and its Moons
Switch to Accurate mode (RK4)

And it breaks?
Are you changing the time step at all?

I found that the simulation is more accurate when the program is focused.

Hmm... that shouldn't have any effect.

There was another thread that came up shortly after this one that answered my question.  Yes I am changing the time step and that is the problem.  I didn't realize there was a cap on the timestep at which point the sim loses accuracy (knew it was too good to be true :p).  And I have discovered the speed-accuracy setting which allows it to go as fast as possible without getting messed up so I guess that answers my question.

So if I get a much faster computer I could speed up the timestep without losing the accuracy?

[Lazareth]

Hmm... that shouldn't have any effect.

Actually, some OSes have this weird idea of raising the thread priority of programs in focus. Most likely to increase GUI responsiveness of whatever the user is working on. Thus it is not unlikely that the simulation is getting less cpu time when it loses focus, resulting in a lower timestep or degraded accuracy.

Of course I have no idea how your program actually works, but this seems like a likely reason to me.

[Dan Dixon]

So if I get a much faster computer I could speed up the timestep without losing the accuracy?

Not exactly... If you get a faster computer you can run the simulation at the same time step (and thus the same accuracy) and it will simulate more quickly as each step will take less real time to simulate.

Actually, some OSes have this weird idea of raising the thread priority of programs in focus. Most likely to increase GUI responsiveness of whatever the user is working on. Thus it is not unlikely that the simulation is getting less cpu time when it loses focus, resulting in a lower timestep or degraded accuracy.

I should have mentioned: When Universe Sandbox loses focus, it sets itself to a lower system priority. If the time step is fixed, Universe Sandbox may run slower, but the accuracy will be unaffected.