At Sun, 27 Jun 2021 21:36:09 +0300, Bogdan Popa wrote: > While I think the complexity piece is important, I feel like it's worth > pointing out just how much more expensive the allocation -- and its > ramifications, like the resulting GC pressure and CPU cache misses -- is > than one might think. Here's a quadratic version of the code that > avoids allocations: > [...] > On my machine (running Racket CS 8.1), this is faster than the > `call-with-output-string` version I posted earlier by about 50ms.
That doesn't sound right to me. Your program does run fast on my machine, but I think it's because this line doesn't have the intended bad effect: > (string-copy! dst 0 dst 0 len) ;; intentionally performing pointless > ;; work to be n^2 A `string-copy!` like this will eventually use the C library's `memmove`, which apparently (and sensibly) doesn't do anything if the source and destination are the same. Try copying to a `dst2` to get quadratic behavior. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/20210627135005.2f6%40sirmail.smtps.cs.utah.edu.
