A process of updating data for a block of an array of data elements stored in an allocated memory region for the block comprises reading in data for a first group of the data elements, updating the data for the first group, and then writing back the updated data to memory. The process can avoid overwriting data for a second group of the data elements that is yet to be read in from the memory region by writing back the updated data for the first group starting at a selected memory address, for example other than the start address of the memory region. The data for the second group of data elements can then be read in and updated, and the updated data can be written back to memory. The process can reduce the amount of memory bandwidth and local cache that needs to be used.