It's just an example - exponential array growth is a *good* solution - if you're using dynamic arrays in such a way then it means you have no idea on the maximum number of elements you need - ergo an exponential growth is a good default mode of operation.
Take a parser that loaded lines of text - it might be asked to load 10 lines and then it might be asked to load 10 million lines - a fixed increment would have to be huge to make this close to efficient in terms of performance and it would then become inefficient in terms of storage for smaller numbers of lines.
Exponential growth is the best trade-off you can make between performance and storage in a number of scenarios - the detriment remains roughly equal across both domains.
In fact a better solution is to have an affordable but reasonably large initial size (say 4096 elements) and then grow exponentially from that - you lose a little bit of storage space for lots of small collections but you minimize the number of resizes as they're all bunched at the lower end with exponential growth.
if you *know* you're storing 1GB of data in memory then you *never* want to be resizing an array of that size anyway - that's just silly - you'd pick a more efficient access pattern in the first place - one that doesn't rely on continuous blocks across the entire set.
Memory is plentiful, you can afford to waste some for the sake of performance.
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