dde23 computation time unexpected behavior

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Mika 2015-5-19

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https://ww2.mathworks.cn/matlabcentral/answers/217563-dde23-computation-time-unexpected-behavior

Dear all,

Consider the following two solutions obtained with dde23:

t =   10e3;
T = 1800e3;
solution_A     = dde23(@large_dde_system,lags,some_initial_condition,[0, t]);
for i=1:(T/t);
    solution_A = dde23(@large_dde_system,lags,solution_A,[i, i+1]*t);
end
solution_B     = dde23(@large_dde_system,lags,some_initial_condition,[0, T]);

I find that solution A is quite fast (a couple of hours) but solution B takes forever (at least a week). In principle (ignoring numerical error) the two solutions should give the same results.

Why is there such a big time discrepancy between A and B? Is this some kind of a memory problem? I would prefer to get Solution B directly, but at the moment it takes way too much time.

Many thanks for any help.