Is it possible to vectorize this loop?

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Adam Frej
Adam Frej 2020-11-30
编辑： Jan 2020-11-30
A = rand(1, 100);
B = rand(1, 100);
w = 0;
for i = 1:length(A)
w = w + A(i).*B;
end

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采纳的回答

Stephan
Stephan 2020-11-30
w_new = (sum(w + A.*B(:),2))';

更多回答（1 个）

Jan
Jan 2020-11-30
编辑：Jan 2020-11-30
A = rand(1, 1000);
B = rand(1, 1000);
tic
for k = 1:1000
w = 0;
for i = 1:length(A)
w = w + A(i).*B;
end
end
toc
tic
for k = 1:1000
w = (sum(A .* B(:),2))';
end
toc
tic
w = 0;
for k = 1:1000
w = sum(A' * B);
end
toc
I get the timings (Matlab online!):
0.34 seconds
0.69 seconds
0.41 seconds
So check it on your machine is the vectorization is an advantage.

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