multiplying a matrix into its transpose

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Mohsen 2012-4-17

评论： Prasad Reddy 2020-4-23

Hi,

I have an sparse and large matrix (A). I would like to do this operation:

C=A*(A');

Using above command takes about 17 sec if size(A)=[31494 277254].

Is there any more efficient command to do the task? Since C matrix will be symmetric so compiler just need to compute half of the C.

Prasad Reddy 2020-4-23

First define matrix c as a zeros matrix of same size and chech if it works.

This is called pre allocation.

Generally preallocation reduces the timeof execution.

command is

C=zeros(31494,277254)

C=A*(A')

if you want to form only half of the matrix then yu can use for lops.

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