abs cannot be used in problem-based optimization expression

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Bruno Luong
Bruno Luong 2023-7-29
评论： Bruno Luong 2023-7-29
Ran in:
Can someone tell me why I cannot use abs() in this simple setup.
prob = optimproblem();
x = optimvar('x',1,1);
y = 1;
x0 = struct('x',0);
prob.Objective = abs(x-y); % sum(abs(x-y)) also doesn't work
Incorrect number or types of inputs or outputs for function 'abs'.
%prob.Objective = norm(x-y,1); % this however works
sol = solve(prob,x0)
If I use prob.Objective = norm(x-y,1) it wokks just fine

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Bruno Luong
Bruno Luong 2023-7-29
  2 个评论
Bruno Luong
Bruno Luong 2023-7-29
Ran in:
Syntaxically it works, but I have to add a small margin to avoid singularity of the derivative at 0
prob = optimproblem();
x = optimvar('x',1,1);
y = 1;
x0 = struct('x',0);
prob.Objective = sqrt((x-y).^2+eps); % sum(abs(x-y)) also doesn't work
sol = solve(prob,x0)
Solving problem using fminunc. Local minimum found. Optimization completed because the size of the gradient is less than the value of the optimality tolerance.
sol = struct with fields:
x: 1

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