For inbuilt solvers ODE23/DDE23, how to keep saving/output all solution values intermediately (eg: every 1 hour, save/output the solution instead of only after reaching tf)

For long run simulations, there is a chance the simulations might stop prematurely after running for a week.

tspan = [0 500];

sol = dde23(@ddefun, lags, @history, tspan);

In that case, if the simulation ends prematurely before t = 500, the above code doesn't return anything. Is there an efficient way to keep saving/outputing the sol at every value of eg., tf = [50, 100, 150...500] so that if the simulation stops, still I can use the sol values saved until that point to restart the simulation

Answer 1

[Bjorn Gustavsson]

You could request output for a selected set of points in time instead of only setting the time-span:

t_all = [0:1:500];
[t_out,Y] = dde23(@ddefun, lags, @history, t_all);

You'll have to judge how many time-steps to include in t_all. It seems a bit strange to me to not get anything out after dde23 quits prematurely, in my work I typically get the [t_out,Y] output up to the point where the ode-integrating functions give up (that is admittedly the odeNN-functions, dde23 might work differently).

HTH

[kim pearson]

So, this will output the state values only at those specific times right, what I also want is the history of states up until these specified times.

Answer 2

[Steven Lord]

Specify an OutputFcn in your dde23 function. Have that OutputFcn log the data to a file.

[kim pearson]

Can you please elaborate. Wouldn’t the same problem occur even with this function?