Blocks updates persistent or state variables while computing outputs

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Matteo Paiano 2021-9-20

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https://ww2.mathworks.cn/matlabcentral/answers/1456854-blocks-updates-persistent-or-state-variables-while-computing-outputs

评论： VIGNESH BALAJI 2024-1-24

In Simulink I had a MATLAB function working properly. I change it a little bit, but now I get the error:

"'DynProg/referenceS/Willners' or the model referenced by it contains blocks that updates persistent or state variables while computing outputs and is not supported in an algebraic loop. The parent subsystem 'DynProg/referenceS' is in an algebraic loop with the following blocks"

function [u_opt,r_des] = optimal_heading(current_X_ASV,X_AUV_list,P_AUV_list,u_max,r_max,Tc_usbl,decisions)
    X = current_X_ASV'; Cost = 0; action = [-1 -1]; LA = -1;
    coder.varsize('expansion',[10000 7], [1 0])
    expansion = [X,Cost,action,LA];
    psi_set = (2*r_max*Tc_usbl).*rand(1,decisions) - r_max*Tc_usbl;
    u_set = u_max.*rand(1,decisions);
    delta_opt = action(1); u_opt = action(2);
    r_des = delta_opt/Tc_usbl;
    

The code is much longer than this, but I tried commenting and uncommenting some lines and I came to the conclusion that the use of rand is somehow responsible for the error. However, if I create a simple function like

function fcn(r_max, Tc_usbl, decisions)
    psi_set = (2*r_max*Tc_usbl).*rand(1,decisions) - r_max*Tc_usbl;
    for k = 1:numel(psi_set)
        delta = psi_set(k)
    end