Loop in perfect foresight context


Does this answer apply to “simul”, too? I am trying to estimate the parameters by matching the deterministic path (rather than the IRF). In each iteration of SMM, I change the parameter value by “set_param_value” and run “simul” to obtain the deterministic transition path. I however wonder whether I also have to recompute and change “initval” and “endval” (i.e., the old and new steady state) in each iteration, because those values must be changed when I change the parameters.


No, things with simul work differently. As you say, you would need to recompute the initial and terminal values.

Thank you for your prompt reply, jpfeifer!

Oh, Really… Do we have a good way to reset “initval” and “endval” before running “simul” in each loop? I mean, how can I reset these values in each iteration as I change the parameter values by “set_param_value”? Thanks.

That depends on how you compute the steady state. In principle, you can just change the first and last entry of

and then loop over


Thank you so much for you reply.

As you point out, I think it depends on how to compute the steady state. My code is like the following. I should:

(1) loop over “perfect_foresight_solver” rather than “simul”, and
(2) compute the steady-state for the initial and end point, and replace the initial and end value of “oo_.endo_simul” by these new steady state values, before running “perfect_foresight_solver”,

I am sorry to ask such a primitive question, but how do I compute the steady-state for both the initial point and the end point outside the mod-file? If I use “steady” after setting a new parameter value, it computes the steady state only at the end point.

Thank you in advance.

-------------- m-file --------------------

%% start iteration

% run dynare    
dynare taxpolicy noclearall;

resit_tx = zeros(ntrial,1); % residual 

for jj = 1:ntrial

    load level0workspace

    resit_tx(jj) ...
        = (y_data(mt,1)-oo_.endo_simul(1,mt)')'/(y_data_sd^2)...
         *(y_data(mt,1)-oo_.endo_simul(1,mt)') ;


---------- mod-file: taxpolicy.mod--------------

<model part>



z_x = 1.0 ; 



z_x = 0.95 ; 


var z_x ;
periods 1     2       3       4       5       6       7       8       9       10      11      12      13      14      15      16      17      18      19      20      21 ;
values 1     0.997438621     0.994883803     0.992335529     0.989793782     0.987258545     0.984729802     0.982207536     0.97969173      0.977182369     0.974679434     0.972182911     0.969692783     0.967209032     0.964731643     0.9622606       0.959795886     0.957337486     0.954885382     0.952439558     0.95;

evalin('base','save level0workspace oo_ M_ options_')


Please provide the full files

Hi, jpfeifer

When we loop over perfect_foresight_solver, do we also need to call perfect_foresight_setup before calling the solver?

When I looped over parameters, changed the first and last entry of oo_.endo_simul, and then called perfect_foresight_solver, the solver failed to converge at some iteration. But when I added `perfect_foresight_setup’, it worked fine.

perfect_foresight_setup should generally only change the initial and terminal condition in oo_endo_simul as well as set up oo_.exo_simul. In most applications you only need to call it once, but it’s hard to make general statements.