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How to speed up large marix multiply?

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Jiuxuan Zhao
Jiuxuan Zhao 2019-6-24
评论： Joss Knight 2019-8-3
Now I have a large matix A and I need to do A*A', how to make this as fast as possible?
eg. A = zeros(40000,1000);
B = A*A';
  2 个评论
Jan
Jan 2019-6-24
Do the matrices have a pattern or are they sparse? Why do you assume that there is anything better than A*A' ?

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回答（1 个）

Matt J
Matt J 2019-6-24
编辑：Matt J 2019-6-24
If you download mtimesx, you can avoid an explicit transpose,
mtimesx SPEED
B=mtimesx(A,A,'c');
  3 个评论
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Jan
Jan 2019-7-8
@Joss: What does "internally supported" exactly mean? Does the JIT acceleration omit the explicit transposition?
Joss Knight
Joss Knight 2019-8-3
It's not the JIT it's the interpreter. When it sees x'*y, x*y', x'*y' or the dot equivalents (.') it calls a special mtimes-transpose operation that includes the information about which arguments are transposed (or conjugate-transposed), rather than applying the transpose operations separately.

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