[masklinn]

Wasn’t there some consideration that with 2x you could never reuse previous contiguous allocations but at 1.4 (ish?) it was an option and improved fragmentation in some cases?

Of course it depends on the behaviour and binning (or lack thereof) of your allocator.

Edit: it’s 1.5, any growth factor below 2 has this property, how far below 2 regulates how quickly it happens, https://github.com/facebook/folly/blob/master/folly/docs/FBV...

> it can be mathematically proven that a growth factor of 2 is rigorously the worst possible because it never allows the vector to reuse any of its previously-allocated memory.

> [...]

> choosing 1.5 as the factor allows memory reuse after 4 reallocations; 1.45 allows memory reuse after 3 reallocations; and 1.3 allows reuse after only 2 reallocations

[dahfizz]

I'm not sure I understand the benefit of this. With a growth factor < 2, you have a chance of getting back chunks of memory that were previously used. That doesn't affect fragmentation / cache hits since all your data is always in the current chunk. What am I missing?