Slowing down when doing calculations with catenated matrix

I'm trying to speed up my code. The original code is here:

I think the "kron" function is repeatedly calculated within the loop "i=1:3", so I moved the kron function outside it:

And it turned out to be slower, even when the use of "kron" is reduced by three times. The reason I found out later is catenating the three copies of "temp" into the third dimension, and I tried the following code:

And this time it's much faster. So my question is why working with catenated matrix is very slow, when the calculation is the same. What in general is to be avoided? Thanks!

Answer 1

[Rashed Mohammed]

Hi Weixin,

Please go through https://www.mathworks.com/help/matlab/matlab_prog/techniques-for-improving-performance.html for improving performance of your code. It outlines the best practices while writing MATLAB code aimed at performance.

Hope this helps.