Enforcing values in ODE solver
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I am trying to solve a stiff ode with ode15s. There is a variable for which there exists a physical constraint due to which it cannot exceed a certain maximum (the allowed maximum also changes with other variables).
I could use events to stop the ode integration and reset the variable but there is a regime where the event persists for some time so, I don't know if exiting the solver each time after just one iteration is efficient.
I also tried using global variables, so that I can always manually control it but then it becomes unphysical when solver rejects a step and goes back.
Is there a way to apply the constraint within the solver? Is there some other solver that could help or would it be better to write one by myself?
Thanks!
1 个评论
I could use events to stop the ode integration and reset the variable but there is a regime where the event persists for some time so, I don't know if exiting the solver each time after just one iteration is efficient.
This is only possible if you define the event as a discontinuous function, and this is not allowed. An allowed event function has a zero crossing without remaining in the state.
回答（1 个）
Walter Roberson
2024-2-27
1 个投票
Use events, and remember that events are only detected when a value crosses the trigger, and are not detected when the system starts in that state.
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