Passing a Global Variable to arrayfun for gpuArray

Question

FARHAN ISLAM 2021-11-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1577960-passing-a-global-variable-to-arrayfun-for-gpuarray

评论： Jens Risbo 2022-2-17

Hi,

I would like to pass a global array to the arrayfun function. While it does work with regular CPU array, it does not work with GPU array. My original code is quite complicated, but I am pasting a simplified code to help you understand what I am trying to do.

Any help on how this can be accomplished is greatly appreciated!

M = randi(500,100,100);
global a
a = [1 2 3];
tic
C = arrayfun(@function_sum,M);
CPUTime = toc
M = gpuArray(M);
tic
C = arrayfun(@function_sum,M);
GPUTime = toc;
Boost = CPUTime/GPUTime
function y = function_sum(x)
global a
y = 0;
for i  = 1 : x
    y = y + 1/i + 1*a(1) + 2*a(2) + 3*a(3);
end
end

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Answer 1

Edric Ellis 2021-11-4

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1577960-passing-a-global-variable-to-arrayfun-for-gpuarray#answer_823570

在 MATLAB Online 中打开

You can do this by using a nested function and variables in the containing parent workspace instead of global variables. Here's how you would apply this to your example. Note that I've made function_sum become a nested function, and it accesses a directly from the containing function workspace.

function repro
M = randi(500,100,100);
a = [1 2 3];
% Nested function
function y = function_sum(x)
y = 0;
for i  = 1 : x
    % Access 'a' directly from parent workspace
    y = y + 1/i + 1*a(1) + 2*a(2) + 3*a(3);
end
end
tic
C = arrayfun(@function_sum,M);
CPUTime = toc
M = gpuArray(M);
tic
C = arrayfun(@function_sum,M);
GPUTime = toc;
Boost = CPUTime/GPUTime
end