How to use Sum and Dot function in GPU computation with arrayfun?

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Viraj Gandhi
Viraj Gandhi 2022 年 12 月 28 日
コメント済み: Joss Knight 2022 年 12 月 29 日
I am trying to find a dot product of two arrays. The given code below is an example. I am new to GPU computing and any help is appreciated.
The main function is:
a = [1,2,3,4];
b = [5,6,7,8];
a=gpuArray(a);
b=gpuArray(b);
funOut = arrayfun(@protoDotProd,a,b);
The function where the dot product is below:
function funOut = protoDotProd(a,b)
cTemp = a+b; % Just an example. In reality, lots of operations
%% option1
% funOut = dot(a,cTemp);
%% option2
% funOutTemp = a.*cTemp;
% funOut = sum(funOutTemp);
%% option3
funOut = sum(a .* cTemp);
None of these options are working and giving me an error:
Error using dotTest
Function passed as first input argument contains unsupported or unknown function 'sum' (or 'dot' for option 1).
For more information see Tips.
Error in 'protoDotProd' (line: 6)

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Joss Knight
Joss Knight 2022 年 12 月 28 日
You cannot perform vector operations in GPU arrayfun. The a and b arguments to your function are not the whole array, they are the scalar values of each element.
Do your element-wise operations ("lots of operations" in your words, followed by the element-wise multiplication) inside your arrayfun function and then do the sum.
Consult the documentation and examples for more info.
  2 件のコメント
Viraj Gandhi
Viraj Gandhi 2022 年 12 月 29 日
I see your point here in "The a and b arguments to your function are not the whole array, they are the scalar values of each element". arrayfun(@protoDotProd,a,b) is almost similar to write
for i=1:n
funOut(i) = protoDotProd(a(i),b(i));
end
Am I correct?
Thanks for your help.
Joss Knight
Joss Knight 2022 年 12 月 29 日
Exactly correct, yes. Except that you can only perform scalar operations on those scalars (so you can't form an array by concatenating the two values for instance).

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