Why is MATLAB 7.6 (R2008a) slow when I use the COLON operator for array indexing to extract a row from a matrix?

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MathWorks Support Team 2009-6-27

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编辑： MathWorks Support Team 2024-4-17

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I am using the COLON operator for array subscripting. In particular, I have a matrix A and I am using

A(i,:)

to obtain the ith row of A. I would like to improve the performance of this operation and make it faster because it exists in a loop with many iterations.

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Answer 1

MathWorks Support Team 2024-4-17

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编辑：MathWorks Support Team 2024-4-17

When processing 2-D or N-D arrays, access your data in columns and store it so that it is easily accessible by columns. Accessing columns is faster than accessing rows due to how matrices are stored in memory.

Please see the following URL for Maximizing Code Performance by Optimizing Memory Access:

https://www.mathworks.com/company/technical-articles/programming-patterns-maximizing-code-performance-by-optimizing-memory-access.html