Solve system of equations without Symbolic Math Toolbox for Compiler

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Daniel Wirth
Daniel Wirth 2022-5-12
回答： Song-Hyun Ji 2023-6-14
I have a system of 3 equations with 3 unknowns (X_sym, AbS_sym, AbB_sym) in my code and I want to solve it for different combinations of variables stored in vlist.
At the moment, I am using 'syms' and 'vpasolve' and it works fine:
syms AbB_sym AbS_sym X_sym
symvar_AbB_sym = parallel.pool.Constant(AbB_sym);
symvar_AbS_sym = parallel.pool.Constant(AbS_sym);
symvar_X_sym = parallel.pool.Constant(X_sym);
parfor i = 1:size(vlist,1)
X_sym = symvar_X_sym.Value;
AbS_sym = symvar_AbS_sym.Value;
AbB_sym = symvar_AbB_sym.Value;
eqns = [(X_sym*AbB_sym*AbS_sym)/(vlist(i,4)*vlist(i,5)) + 2*(X_sym*AbS_sym^2)/vlist(i,5)^2 + ...
(X_sym*AbS_sym)/vlist(i,5) + AbS_sym == vlist(i,1),...
(X_sym*AbB_sym*AbS_sym)/(vlist(i,4)*vlist(i,5)) + 2*(X_sym*AbB_sym^2)/vlist(i,4)^2 + ...
(X_sym*AbB_sym)/vlist(i,4) + AbB_sym == vlist(i,2),...
(X_sym*AbB_sym*AbS_sym)/(vlist(i,4)*vlist(i,5)) + (X_sym*AbB_sym^2)/vlist(i,4)^2 + ...
(X_sym*AbS_sym^2)/vlist(i,5)^2 + ...
(X_sym*AbB_sym)/vlist(i,4) + (X_sym*AbS_sym)/vlist(i,5) + X_sym == vlist(i,3)];
S = vpasolve(eqns,[X_sym AbB_sym AbS_sym],[0 Inf; 0 Inf;0 Inf]);
X(i,1) = S.X_sym;
AbB(i,1) = S.AbB_sym;
AbS(i,1) = S.AbS_sym;
end
However, I cannot use this approach, as I cannot compile my app into a standalone app with syms and vpasolve.
I tried looking into 'matlabfunction' according to this article:
https://de.mathworks.com/help/symbolic/deploy-generated-matlab-function-from-symbolic-expression.html
But I don't think it is applicable here since I have a system of equations. Am I right?
How can I modify the code so it could be compiled into a standalone app?
Any help is appreciated! Thanks!

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采纳的回答

Torsten
Torsten 2022-5-12
Did you try "solve" on your system of equations with the numerical vlist coeffcients replaced also by symbolic variables ?
syms AbB_sym AbS_sym X_sym vlist1 vlist2 vlist3 vlist4 vlist5
eqns = [(X_sym*AbB_sym*AbS_sym)/(vlist4*vlist5) + 2*(X_sym*AbS_sym^2)/vlist5^2 + ...
(X_sym*AbS_sym)/vlist5 + AbS_sym == vlist1,...
(X_sym*AbB_sym*AbS_sym)/(vlist4*vlist5) + 2*(X_sym*AbB_sym^2)/vlist4^2 + ...
(X_sym*AbB_sym)/vlist4 + AbB_sym == vlist2,...
(X_sym*AbB_sym*AbS_sym)/(vlist4*vlist5) + (X_sym*AbB_sym^2)/vlist4^2 + ...
(X_sym*AbS_sym^2)/vlist5^2 + ...
(X_sym*AbB_sym)/vlist4 + (X_sym*AbS_sym)/vlist5 + X_sym == vlist3];
S = solve(eqns,[X_sym AbB_sym AbS_sym])
If this does not work, you will have to use the numerical solver "fsolve" for your system of equations.
  1 个评论
Daniel Wirth
Daniel Wirth 2022-5-13
Thanks for your answer!
Yes, I did try solving the equations with 'solve' first, but that didn't work...
I ended up going with your suggestion of using fsolve and it worked like a charm! Thanks a lot!!

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更多回答（1 个）

Song-Hyun Ji
Song-Hyun Ji 2023-6-14
You can get the solution in the following answers page.
- How to deploy when using 'syms' and 'solve' with function input arguments to consist the equation in MATLAB Compiler
https://www.mathworks.com/matlabcentral/answers/1982214-how-to-deploy-when-using-syms-and-solve-with-function-input-arguments-to-consist-the-equation-in

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