MATLAB: PARFOR Transparency violation error

parfor

Why am I getting the transperancy error for the following code?
Error using syms (line 216)
Transparency violation error.
See Parallel Computing Toolbox documentation about Transparency
clc 
clear
alpha =4; % Path loss exponent
del = 2/alpha;
R =1;
N = 4;
p_k = [0.15 0.05 0.45 0.35];
epsi = 1;
N_set = 1:N;
lambda_dash = 0.05:0.05:0.5;
spec_eff1 = zeros(length(lambda_dash),N);
parfor vv = 1:length(lambda_dash)
    vv
comm_term = lambda_dash(vv)*pi*(epsi+R^alpha).*gamma(1+del)*gamma(1-del);
syms tt
fun_int1 = zeros(1,N);
for k = 1:N
term = 0;
for ii = 1:N
    m =max(ii-N+k,0):1:min(k,ii);
    p_intf = (factorial(k)./(factorial(m).*factorial(k-m))).*(factorial(N-k)./(factorial(ii-m).*factorial(N-k-ii+m)))./(factorial(N)./(factorial(ii).*factorial(N-ii)));
    term =term + (sum(p_k(ii).*p_intf.*((2^(tt)-1).*m./k).*((epsi+R^alpha).*(2^(tt)-1).*(m./k) + epsi).^(del-1)));
end
f = exp(-comm_term.*term);
fun_int1(k) = vpa(int(f,[0 inf]));
end
spec_eff1(vv,:) = fun_int1;
end
spec_eff = sum(p_k.*spec_eff1,2);
semilogy(lambda_dash,spec_eff,'k-')
hold on
grid on

Best Answer

The problem occurs in this line:
syms tt
Although the syms function is very handy for hacking symbolic math on your client machine, it modifies the global state of the workspace in a way that is not suitable for parallel computations (and parfor in particular). For parallel computations, use the sym object constructor and change that line to:
tt = sym('tt');
In general, with parfor it's better to use functions that construct and return objects (like the function sym), which are transparent in most cases.
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