# How to use the parfor function inside a for loop?

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Yro 2021 年 10 月 29 日

Hi, I am trying to use the parfor function for parallel calculation inside a for loop. I have a problem to define the variables inside and outside the loop. The following code is a simulated annealing algorithm for optimization. The main problem is for the variables inside the parfor loop for parallel computation, specifically the newsol variable. How can I define this variable correctly?
%% SA Main Loop
for it = 1:iters
pf_sol = sol;
pf_position = sol.Position;
pf_cost = sol.Cost;
pf_BestCost = BestCost;
parfor subit = 1:subiters
pf_sol = sol;
% Create new solution
newsol.Position = Neighbor(pf_position);
newsol.Cost = ObjectiveFunction(newsol.Position);
DELTA = -(newsol.Cost-pf_cost);
if DELTA <= 0
pf_sol = newsol;
else
P = exp(-DELTA/T);
if rand <= P
pf_sol = newsol;
end
end
% Update Best Solution
if pf_sol.Cost >= pf_BestSol.Cost
Pf_BestSol = pf_sol;
end
end
% Store Best
BestCost(it) = BestSol.Cost;
% Display
disp(['Iteration ' num2str(it) ': Best = ' num2str(BestCost(it))]);
% Update temperature
T = T*alpha;
end

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### 回答 (1 件)

Raymond Norris 2021 年 10 月 29 日
There's a bit of missing code here and some of it doesn't make quite sense, so I might be off on my solution. And, I'm going to assume that newsol is a structure and not an object. If so, trying making the following changes.
From
newsol.Position = Neighbor(pf_position);
newsol.Cost = ObjectiveFunction(newsol.Position);
To
position = Neighbor(pf_position);
cost = ObjectiveFunction(position);
newsol = struct('Position',position,'Cost',cost);

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