How to assign values to an array with broadcasting

hi in the code bwloe i recieve a message in

xi1 = x1(index_i);

xi2 = x2(index_i);

i receieve a warning

function   [Is]=currentMoM()
%UNTITLED2 Summary of this function goes here
%   Detailed explanation goes here
[f,N,ra,k0,Z0,lambda,gap_angle] = parameter();
gamma_const=1.781;
%Phi0=zeros(N);
e=exp(1);
dftm=(2.*gap_angle)/(N-1);
n=1:N;
Phi0=-gap_angle+(n-1).*dftm;
%for jj = 1:N
%Phi0(jj)=(jj-1).*dftm;
%end
x1 = Phi0(:); % Create a column vector of x1 values
x2 = x1 + dftm; % x2 values depend on x1  
lmn=zeros(N,N);
gm = zeros(1,N);
zmn = zeros(N,N);
%opts = optimset('RelTol', 1e-6, 'AbsTol', 1e-6);
%vim = zeros(1,N);
%vsn = zeros(1,N);
coeif=(Z0.*k0./4).*ra.*dftm;
coeifn=(Z0./2).*sin(k0.*ra.*dftm./2);
B=(4./(Z0.*k0));
A=(gamma_const./2).*k0.*ra;
parfor idx = 1:N*N
    % Convert linear index to subscripts
    [index_i, index_j] = ind2sub([N, N], idx);
    
    % Precompute integration bounds
    xi1 = x1(index_i); 
    xi2 = x2(index_i);
    xj1 = x1(index_j); 
    xj2 = x2(index_j);
    
    if index_i == index_j
        % Handle diagonal elements
        funa = @(x, y) triangle_basisn(x, index_i) .* triangle_basisn(y, index_j) .* ...
            ra .* (1 - 1i .* (2/pi).* (log(A) + log(abs(x - y + 1e-10)))); 
        
        
        
        lmn(idx) = integral2(funa, xi1, xi2, xj1, xj2, 'RelTol', 1e-6, 'AbsTol', 1e-6);
    else
        % Handle off-diagonal elements
        funb = @(x, y) triangle_basisn(x, index_i) .* triangle_basisn(y, index_j) .* ...
            ra .* besselh(0, 2, k0 .* ra .* sqrt(2 - 2 .* cos(x - y)) +1e-9)
        
        
        
        lmn(idx) = integral2(funb, xi1, xi2, xj1, xj2, 'RelTol', 1e-6, 'AbsTol', 1e-6);
        
        
    end
    
    % Assign to zmn
    zmn(idx) = lmn(idx);
    
end
% Reshape the result back to a 2D matrix
lmn = reshape(lmn, [N, N]);
zmn = reshape(zmn, [N, N]);

% Compute gm vector
parfor index_i = 1:N
    func = @(x) B .* triangle_basisn(x, index_i) .* Efieldin(x);
    gm(index_i) = integral(func, x1(index_i), x2(index_i), 'RelTol', 1e-6, 'AbsTol', 1e-6);
end
% Solve linear system
Is = linsolve(zmn, gm');
end

Answer 1

[Walter Roberson]

    xi1 = x1(index_i); 
    xi2 = x2(index_i);
    xj1 = x1(index_j); 
    xj2 = x2(index_j);

You access x1 and x2 at two different locations. If you were to only access each of them at one location and that one location could be calculated through simple arithmetic on the parfor variable, then hypothetically you could probably slice the variable. But as it is, indexing at two different locations and that location determined by non-trivial calculations on the parfor variable... the only option is for the arrays to be broadcast arrays.

[Walter Roberson]

You should consider instead using

lmn = zeros(N,N);
for index_j = 1:N
    xj1 = x1(index_j); 
    xj2 = x2(index_j);
    lmn_i = zeros(N,1);
    parfor index_i = 1:N
        xi1 = x1(index_i); 
        xi2 = x2(index_i);
        stuff to calcuate lmn_i(index_i)
    end
    lmn(:,index_i) = lmn_i;
end

This might have a little more wait time, of parfor workers having finished and sitting idle waiting for the rest of the workers to finish... but it will be more efficient on passing values to the workers.

[george veropoulos]

thank ! where put this in my code ?

[george veropoulos]

if a change parfor with for the waring is vanish

[Walter Roberson]

I do not understand why zmn(idx) = lmn(idx)

function   [Is]=currentMoM()
%UNTITLED2 Summary of this function goes here
%   Detailed explanation goes here
[f,N,ra,k0,Z0,lambda,gap_angle] = parameter();
gamma_const=1.781;
%Phi0=zeros(N);
e=exp(1);
dftm=(2.*gap_angle)/(N-1);
n=1:N;
Phi0=-gap_angle+(n-1).*dftm;
%for jj = 1:N
%Phi0(jj)=(jj-1).*dftm;
%end
x1 = Phi0(:); % Create a column vector of x1 values
x2 = x1 + dftm; % x2 values depend on x1  
lmn=zeros(N,N);
gm = zeros(1,N);
zmn = zeros(N,N);
%opts = optimset('RelTol', 1e-6, 'AbsTol', 1e-6);
%vim = zeros(1,N);
%vsn = zeros(1,N);
coeif=(Z0.*k0./4).*ra.*dftm;
coeifn=(Z0./2).*sin(k0.*ra.*dftm./2);
B=(4./(Z0.*k0));
A=(gamma_const./2).*k0.*ra;
lmn = zeros(N,N);
for index_j = 1:N
    xj1 = x1(index_j); 
    xj2 = x2(index_j);
    lmn_i = zeros(N,1);

    parfor index_i = 1:N
    
        % Precompute integration bounds
        xi1 = x1(index_i); 
        xi2 = x2(index_i);

    
    if index_i == index_j
        % Handle diagonal elements
        funa = @(x, y) triangle_basisn(x, index_i) .* triangle_basisn(y, index_j) .* ...
            ra .* (1 - 1i .* (2/pi).* (log(A) + log(abs(x - y + 1e-10)))); 
        
        
        lmn_ii = 
        lmn_i(index_i) = integral2(funa, xi1, xi2, xj1, xj2, 'RelTol', 1e-6, 'AbsTol', 1e-6);
    else
        % Handle off-diagonal elements
        funb = @(x, y) triangle_basisn(x, index_i) .* triangle_basisn(y, index_j) .* ...
            ra .* besselh(0, 2, k0 .* ra .* sqrt(2 - 2 .* cos(x - y)) +1e-9)
        lmn_ii = integral2(funb, xi1, xi2, xj1, xj2, 'RelTol', 1e-6, 'AbsTol', 1e-6);
        
    end
    lmn_i(index_i) = lmn_ii;
    end
    lmn(:,index_i) = lmn_i;
end

zmn = lmn;

% Compute gm vector
parfor index_i = 1:N
    func = @(x) B .* triangle_basisn(x, index_i) .* Efieldin(x);
    gm(index_i) = integral(func, x1(index_i), x2(index_i), 'RelTol', 1e-6, 'AbsTol', 1e-6);
end
% Solve linear system
Is = linsolve(zmn, gm');
end

[george veropoulos]

yes does not need