Running a script multiple times and recording outputs for each of the runs separately

Hi all,

I'm having a function (say A) that generates a random n by n matrix (I need the value of n=8) and I use those numbers to calculate a cost function (B). So I need to run the first function A multiple times (lets say 1000 times) giving me 1000 different 8 by 8 matrices of random numbers and then calculating the cost function using those 1000 different matrices.

Here is my A function:

function [S]=main23(n)
%// n - matrix size (in my case it's 8)
[ ii jj ] = ndgrid(1:n); %// rows and columns of S
ii = ii(:);
jj = jj(:);
success = 0; %// ...for now
attempt = 0; %// attempt count (not really needed)
while ~success
    attempt = attempt + 1;
    S = NaN(n, n); %// initiallize result. NaN means position not filled yet
    t = 1; %// number t is being placed within S ...
    u = 1; %// ... for the u-th time
    mask = true(1, numel(ii)); %// initiallize mask of available positions
    while any(mask) %// while there are available positions
        available = find(mask); %// find available positions
        r = randi(numel(available), 1); %// pick one available position
        itu = ii(available(r)); %// row of t, u-th time 
        jtu = jj(available(r)); %// col of t, u-th time
        S(itu, jtu) = t; %// store t at that position
        remove = (ii==itu) | (jj==jtu);
        mask(remove) = false; %// update mask of positions available for t
        u = u+1; %// next u
        if u > n %// we are done with number t
            t = t+1; %// let's go with new t
            u = 1; %// initiallize u
            mask = isnan(S(:)); %// initiallize mask for this t
        end
        if t > n %// we are done with all numbers
            success = 1; %// exit outer loop (inner will be exited too)
        end
    end
end

So I need this function to run 1000 times for example and to record each of the 1000 matrices. Any idea, please?

Thank you.

Answer 1

[Rik]

If your code takes a very long time you might go for saving each result to a separate mat file. This would also enable running the code concurrently on different machines, provided that they share some disk. (generate file names with something like sprintf('%sresult%05d.mat',currentPath,currentCount))

Another option is to save the results in one cell array.

[Uros Jovanovic]

Could you explain a little bit, please? I need to run the whole code above for about 1000 times, don't know how to do that, and to record each of the matrices that I get from running the above code 1000 times. I mean, is there a faster way than just clicking on the execute button 1000 times?

Answer 2

[Image Analyst]

Try this:

for k = 1 : 1000
    S{k}=main23(n);
end

[Uros Jovanovic]

Thanks, but it reports this error:

Cell contents assignment to a non-cell array object.

Any thoughts?

[Walter Roberson]

You could get that error if you tried to add that code inside your main23 routine, because you use S as a numeric variable there. However, outside of main23 you would only get that error if you had previously assigned a numeric value to S.

numrun = 1000;
S = cell(numrun, 1);
for k = 1 : numrun
    S{k}=main23(n);
end

[Uros Jovanovic]

Thanks, but now I need to transform these cell arrays into matrices. In other words, each of the cell array needs to be a matrix (for example s(1)=S{1}), any thoughts?

[José-Luis]

https://se.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html