Unexpected matlab operator when using Matlab Coder

I use Matlab Coder to generate mex file, but in the middle of process I got error message "Unexpected MATLAB operator" that is indicate ":" in my code

 if (abs(permlist(jj,:)-iv))==0
           c(jj) = c(jj) + 1 ;
        %end
 end

Does anyone know how to solve it?

[Aditya]

Hi Nirwana,

I have tried to use the same code for code generation, and it was working fine without any issues. Below is the sample code that I have tried:

function c = test_reproduce_error(permlist, iv)
    % Initialize output array
    c = zeros(size(permlist, 1), 1);
    
    % Loop through rows of permlist
    for jj = 1:size(permlist, 1)
        % Problematic line of code
        if abs(permlist(jj,:) - iv) == 0
            c(jj) = c(jj) + 1;
        end
    end
end

If possible, could you provide the complete code file that is generating this issue?

[nirwana]

Hi @Aditya, thanks for the answered, but I still did not solve the issues.

Here is my complete code, It it work well it should give the result 0.9390.

function result = myfunc(data,m,L)
len = length(data);
no_vector = len - (m-1)*L ;
mm = factorial(m);
coder.extrinsic('perms'); 
permlist = perms(1:m);
c=zeros(1,mm);
a=zeros(1,m); 
%loop over number of vectors
for i=1:no_vector
    %find co-ordinates of each point in m-space
    for j=1:m
        a(j) = data(i+(j-1)*L);
    end
    %sort co-ordinates in ascending order  
    [~,iv] = sort(a,'ascend'); %"iv" is the indice of sorted co-ordinates 
    %compare pattern with permutation list
        for jj=1:mm
          if (abs(permlist(jj,:)-iv))==0
          c(jj) = c(jj) + 1 ;
          end
        end
end
c = c/no_vector;
pe = 0;
for k=1:mm
    if c(k) ~= 0
       pe = pe - c(k)*log(c(k));
    end
end
%normalize 
result = pe/log(mm);

I use test_code

clear all

tic
data=load('HHZ__20150101T034000Z__20150101T040000Z.DAT');
myfunc(data,5,3)
toc

Answer 1

[Aditya]

Hi @nirwana,

Thanks for providing the file. It seems that you are using mxArray in your code, which has certain restrictions and rules that we need to keep in mind. Specifically, there are some issues in code generation (codegen) when we use mxArray directly in some expressions. It is better to convert the array to a native MATLAB type, such as double, before using it.

Here's the modified file with the provided solution that you can use:

function result = myfunc(data,m,L)
len = length(data);
no_vector = len - (m-1)*L ;
mm = factorial(m);
coder.extrinsic('perms');

% Generate permutation list using feval
temp_permlist = perms(1:m);

% Preallocate permlist as a native MATLAB array
permlist = zeros(mm, m);

% Extract values from temp_permlist into permlist
for i = 1:mm
    for j = 1:m
        permlist(i, j) = temp_permlist(i, j);
    end
end
c=zeros(1,mm);
a=zeros(1,m);
%loop over number of vectors
for i=1:no_vector
    %find co-ordinates of each point in m-space
    for j=1:m
        a(j) = data(i+(j-1)*L);
    end
    %sort co-ordinates in ascending order
    [~,iv] = sort(a,'ascend'); %"iv" is the indice of sorted co-ordinates
    %compare pattern with permutation list
    for jj=1:mm
        if (abs(permlist(jj,:)-iv))==0
            c(jj) = c(jj) + 1 ;
        end
    end
end
c = c/no_vector;
pe = 0;
for k=1:mm
    if c(k) ~= 0
        pe = pe - c(k)*log(c(k));
    end
end
%normalize
result = pe/log(mm);

please refer to this link on how to use mxArray: Working with mxArray

Hope this helps!

[nirwana]

Thanks for providing solution, but when I try to generate mex file by matlab coder using your solution, some another error appear

line 8 : The extrinsic function 'perms' is not available for standalone code generation. It must be eliminated for stand-alone code to be generated. It could not be eliminated because its outputs appear to influence the calling function. Fix this error by not using 'perms' or by ensuring that its outputs are unused.

line 16 : The extrinsic function 'coder.internal.mxSubscript' is not available for standalone code generation. It must be eliminated for stand-alone code to be generated. It could not be eliminated because its outputs appear to influence the calling function. Fix this error by not using 'coder.internal.mxSubscript' or by ensuring that its outputs are unused.

the solution that matlab coder offer ("not using perm or not using coder internal") is something that might affect the result.

Other things that I should add is I use input tipe as below

data double(:inf x 1) --> I use infinity because this function will applied to another data that the length may vary.

m double(1 x 1)

L double(1 x 1)

Does the error msg that appear affected by input type that I use?

[Aditya]

Hi @nirwana,

could you tell me the MATLAB version that you are using?

[nirwana]

I use R2022b