On Sun, Sep 5, 2021 at 1:34 PM 'Dan Kortschak' via golang-nuts < golang-nuts@googlegroups.com> wrote:
> On Sun, 2021-09-05 at 13:09 +0200, 'Axel Wagner' via golang-nuts wrote: > > This sounds interesting, but I don't understand it. Would you be > > willing to expand on this? > > It's a consequence of the sum of successive powers of two. To have > reached an allocation of 2^n slots assuming a doubling n times you must > have deallocated and moved 2^n-1 total slots \sum(2^0, 2^1, 2^2, ..., > 2^(n-1)). This is less than the amount of space that you are using now, > by one slot, so by definition you will not be able to use any of that > space. Nifty. Good to learn new things :) There is a discussion here, which justifies the use of φ, somewhat convincingly: https://archive.li/Z2R8w Does Go use this? Naively, the way `append` works we can't re-use the storage anyway (as it might be aliased by a different slice), so ISTM doing this would require at least cooperation from the compiler to do alias analysis and make sure we are not keeping the slice around elsewhere. It *seems* like a sort of optimization Go doesn't do, but you would know better, I think. > Note that here "slots" is any arbitrary number of contiguous > bytes. > > This is pessimistic and only deals with allocations associated with a > single growing array, discounting the possibility of recovering from > unused allocations elsewhere. > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/ba45f293129926415fa8e83c53d680f53bb009c7.camel%40kortschak.io > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAEkBMfFmfQEgjF5FgCbQKCvPSGKbczZZ3Ac5RdSaH7%2BYT90LeA%40mail.gmail.com.
