Can I supply a gradient to fmincon when my objective function is anonymous?
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DavidZ
el 13 de Ag. de 2014
Comentada: Rustem Devletov
el 26 de Abr. de 2019
I am using fmincon and would like to supply a gradient for the objective function to speed up convergence. The trouble is I use an anonymous objective function so I can pass parameters to my real objective function. I believe the anonymous function only picks up the first argument of my real objective function, which is the function value and not the gradient. The basic structure of my code is:
if true
%%%%%%%%%%%%%%%%%%%
[f,gradf]=realobjective(parameters,x]
f=blah;
gradf=blah;
end
%%%%%%%%%%%%%%%%%%%
options=optimoptions(@fmincon,'Algorithm','active-set','MaxFunEvals',1E5,'MaxIter',1E5,'TolFun',1E-6,'TolX',1E-6,'GradConstr','on','GradObj','on');
xguess=0;
func=@(x)realobjective(parameters,x)
argmin=fmincon(func,xguess,[],[],[],[],0,1000,nonlconstr,options)
end
So I think fmincon is not using the gradient I have defined in the real objective function. I'd be incredibly grateful for any advice.
David
1 comentario
Rustem Devletov
el 26 de Abr. de 2019
Hey, friend! I'm a fourth year student in Russia, currently writing my thesis. My supervisor asked me to provide gradient to fmincon
I have triend smth like this
function F = rosenbrockwithgrad(x)
F = 100*(x(2) - x(1)^2)^2 + (1-x(1))^2;
if nargout > 1 % gradient required
g = [-400*(x(2)-x(1)^2)*x(1)-2*(1-x(1));
200*(x(2)-x(1)^2)];
end
But he said that he wants it to be found in another file. How can I implement this? How do I find gradient in one file and pass it to another one?
Respuesta aceptada
Matt J
el 13 de Ag. de 2014
Editada: Matt J
el 13 de Ag. de 2014
What you've posted looks fine. Call nargout inside realobjective (e.g., at a breakpoint), to test whether fmincon is calling it with two output arguments.
5 comentarios
Matt J
el 13 de Ag. de 2014
Did you try running with 'DerivativeCheck' set to 'on' to validate your gradient calculation? Sounds like your constraint gradient calculation is working okay, but the objective function gradient calculation might have errors.
Rustem Devletov
el 26 de Abr. de 2019
Hey, friend! I'm a fourth year student in Russia, currently writing my thesis. My supervisor asked me to provide gradient to fmincon
I have triend smth like this
function F = rosenbrockwithgrad(x)
F = 100*(x(2) - x(1)^2)^2 + (1-x(1))^2;
if nargout > 1 % gradient required
g = [-400*(x(2)-x(1)^2)*x(1)-2*(1-x(1));
200*(x(2)-x(1)^2)];
end
But he said that he wants it to be found in another file. How can I implement this? How do I find gradient in one file and pass it to another one?
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