Error using mupadengin​e/feval_in​ternal Invalid input. Expected ']'. Error in mupadengine/feval

I am using the following program given at sums-of-squares.github.io/sos/:

syms x y s t;
p = s*x^6 + t*y^6 - x^4*y^2 - x^2*y^4 - x^4 + 3*x^2*y^2 - y^4 - x^2 - y^2 + 1
prog = sosprogram([x;y], [s;t]);
prog = sosineq(prog, p); % p is sos
prog = sossolve(prog, options);
sosgetsol(prog, [s,t])

I am getting error at (prog = sosineq(prog, p); % p is sos) this line which is as follows:

Error using mupadengine/feval_internal

Invalid input. Expected ']'.

Error in mupadengine/feval

Error in sosconstr (line 65)

degcheck = feval(symengine,'collect',degcheck,charvartable);

Error in sosineq (line 105)

sos = sosconstr(sos,'ineq',symexpr);

Error in sostest1 (line 5)

prog = sosineq(prog, p); % p is sos

I cannot figure out the problem. The same problem occurs with some of the other demos of sostoolbox. For example the sosdemo2.m also gives the error

Error using mupadengine/feval_internal

Invalid input. Expected ')'.

Error in mupadengine/feval

Any help would be appreciated.

[Jason Zhou]

I have similar question right now. Have you figured it out?

[Saad Hamayoon]

Yeah. It is the problem with the Matlab version. I ran the same code on Matlab 2015 and it worked. I guess SOSTOOLS need to be updated before it can be used in MATLAB 2020.

[Venkatraman Renganathan]

Hi, I am having the same issue. Please let me know if this has been resolved. Else, I have to get back to MATLAB older version to run my code.

Answer 1

[Walter Roberson]

Change

prog = sosprogram([x;y], [s;t]);

to

prog = sosprogram([x,y], [s,t]);

Also, your code does not define options, so your sample code will fail at that point.

[Saad Hamayoon]

Thank you. It does resolve the issue for this example. But sosdemo2 or the following example does not work with the solution that you have proposed. It is example 2 (b) at https://sums-of-squares.github.io/sos/

syms x y s t;
options.solver = 'sedumi'
p = s*x^6 + t*y^6 - x^4*y^2 - x^2*y^4 - x^4 + 3*x^2*y^2 - y^4 - x^2 - y^2 + 1
prog = sosprogram([x,y], [s,t]);
prog = sosineq(prog, p);     % p is sos
prog = sossetobj(prog, s+t); % minimizes s+t
prog = sossolve(prog, options);
sosgetsol(prog, [s,t])

The above example gives the following error, however, decision variables have been defined:

Error using sossetobj (line 65)

There is unknown decision variable

Error in sostest1 (line 29)

prog = sossetobj(prog, (s+t)); % minimizes s+t

Note: All these examples work fine in the older version of MATLAB.

[Walter Roberson]

sym2chartable.m needs to be adjusted.

In a range of versions, char() applied to a symbolic list of variables [s t] would return 'matrix([s,t])' and the code would strip off all the [ and ] and then change the remaining 'matrix(s,t)' to '[s,t]' .

In sufficiently new versions, char() applied to a symbolic list of variables [s t] would return '[s,t]'. The code would strip off all the [ and ] to get 's,t' but then since there is no 'matrix(' or trailing ')' the '[' and ']' do not get wrapped.

I would suggest adding at the end

if chartable(1) ~= '['
    chartable = ['[' chartable];
end
if chartable(end) ~= ']'
    chartable = [chartable ']'];
end

[Saad Hamayoon]

Thank you for the explanation. I will try this :)