matlab - parfor 和句柄类

Question

我有一个句柄类:

classdef A<handle


    properties
        a;
    end

    methods
        function obj = A(a)
            obj.a=a;
        end
    end
end

我有一个 A 对象的元胞数组:

arr={};
for i=1:3
    arr{i}=A(i);
end

我想做的是将该元胞数组传递给 parfor 循环，以便每个对象的值都会发生变化:

parfor i=1:3
    arr{i}.a=i*5;
end

然而，这段代码根本没有改变arr。事实上，here它指出

Changes made to handle classes on the workers during loop iterations are not automatically propagated to the client.

我怎样才能克服这个问题？

Answer 1

一个有趣的问题；我实际上从未遇到过这个问题。了解关于 parfor 限制的一切总是好的，所以我做了一些谷歌搜索并想出了 this :

I have received an answer to this issue from technical support. Apparently the Mathworks regard it as a 'feature' that changes to objects are not returned - though I can't see that it's a very useful feature. Anyway, the way to get modified class properties returned from a parfor loop is to make an explicit change which can be recognised by parfor. Here are two examples which work for the above example object:

parfor n = 1:num
    exArray(n).data = n:n+5;
end

or

parfor n = 1:num
    temp = exArray(n);
    setData(temp,n:n+5);
    exArray(n) = temp;
end

Actually, if you change any object property it also seems to work. So for example this also works, if there is a second property data2 which is set explicitly, both data and data2 are correctly returned:

  parfor n = 1:num
      setData(exArray(n),n:n+5);
      exArray(n).data2 = n:n+5;
  end

示例对象由

给出

classdef Example < handle

    properties
        data
    end

    methods
        function obj = Example(data)
            obj.data = data;
        end

        function setData(obj,data)
            obj.data = data;
        end

        function data = getData(obj)
            data = obj.data;
        end
    end
end

并且数组被简单地初始化为

% Initialise array of objects
for n = 1:num
    exArray(n) = Example(zeros(1,6));
end