(revised) What is the right way to apply parallel.pool.Constant on functional handle?

Question

Simon 2023-7-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2000802-revised-what-is-the-right-way-to-apply-parallel-pool-constant-on-functional-handle

评论： Simon 2023-7-27

(original question) I use parfor-loop to process through rows of table/array. In each iteration, a function handle is called to do that. But this leads to a warning message that the function handle is 'a broadcast variabe' and might 'result in unnecessary communication overhead.' Is there a solution to avoid that?

(revised question) I tried parallel.pool.Constant(function_handle), and it generates an error message when calling the function: "Error using [my iteration function]. Unable to use a value of type string as an index." What is the right way to use parallel.pool.Constant(function_handle)?

function res = iteration(f, A)
% f is a function handle
C = cell(height(A),1);
parfor row = 1:height(A)
    C{row} = f(A{row,:}); % f is a broadcast variable
end
res = vertcat(C{:});
end

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Walter Roberson 2023-7-27

在 MATLAB Online 中打开

function res = iteration(f, T)
% f is a function handle
C = cell(height(T),1);
%%%%%% adding this line would generate an error message
fh = parallel.pool.Constant(f); 
parfor row = 1:height(T)
    C{row} = fh.Value(T{row,:});
end
res = vertcat(C{:});
end

Note: see also rowfun

Simon 2023-7-27

@Walter Roberson Thanks for your help. Glad to learn a new thing. As for rowfun, I used it before but found it was too cumbersome in terms of input arguments. And it does not allow parfor, so I try to make a simpler parfor version for my own usage.

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Answer 1

Simon 2023-7-27

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2000802-revised-what-is-the-right-way-to-apply-parallel-pool-constant-on-functional-handle#answer_1279522

在 MATLAB Online 中打开

I think I found the solution: feval(). It's in the help page of broadcast variable and parfor.

function res = iter_test(f, T)
% f is a function handle
C = cell(height(T), 1);
parfor row = 1:height(T)
    C{row} = feval(f, T{row, :});   
end
res = vertcat(C{:});
end