Alternative to EVAL string expressions in optimization

Hi,

I have a huge matrix, each element is a string like "16*q^2+4*q", i call it new_sol_array, now i want to define multiple optimconstr object with each row one set of constraints. This is what i did:

constr= optimconstr(M,N);

for i=1:rows

for j =1:column

constr(i,j)=eval(new_sol_array(i,j)+'==0');

end

end

As you would see, this is extremely slow. Is there a better alternative to do the same thing? i have read some of the answers about eval on this website yet did not find anything relevant enough to my problem.

Thank you so much!!!

Answer 1

[Walter Roberson]

Instead of eval() everything, use file operations to emit a file along the lines of

constr = [
   EQN, EQN,... EQN
   EQN, EQN,... EQN
]

along with a function header. Then "clear" the name of the file. Then invoke the file as a function passing in q and whatever else is required

This reduces the burden by not needing to eval() each one individually.

[Kylekk]

Thank you so much for your comment Walter! I'm not sure i understand your answer correctly so i'm just gonna repeat what you said and please correct me if i'm wrong.

1. Write a text file maybe with content like

constr = [
   16*q^2+4*q==0, 25*q*t+20*t==0,... EQN
   EQN, EQN,... EQN
]

2. Read this text file, substitute in variables (this step i'm actually not sure how to do, could you be more specific?)

3. Evaluate this one-hell-of-a-long line of command only once by eval.

Is that so? Appreciate it!

[Kylekk]

Just to update. I tried

temp = new_sol_array+'==0';
temp = join(join(temp,2),';',1);
temp = 'constr=['+temp+']';
eval(temp);

It took me less than 3 min to assign 10000 by 10 constraints. Not perfect but definitely acceptable.

[Stephen23]

1. yes
2. no
3. no

Did you try writing a function file and calling it, as Walter Roberson described?

[Kylekk]

Thank you Stephen, I did not do that simply because I don't get the idea. What kind of function file are you talking about? I have only a string array, why would a function takes variable names as input help?