Row-major and column-major order

In computing, row-major order and column-major order are methods for storing multidimensional arrays in memory.

Memory layout, together with memory access pattern, is very important for program's performance.

Best performance is obtained when the layout matches the memory access pattern, i.e. iterating through a column-major stored matrix column-wise and through a row-major stored matrix row-wise. This will make for sequential memory access and the best performance. Techniques like loop interchange can be used to change the memory access pattern.