Comment by Sesse__
9 hours ago
It's 60% faster (0.6x faster, 1.6x as fast). Throughput (“how much stuff you can do per unit of time”) is the only reasonable way to describe performance[1], otherwise large speedups are basically impossible to describe in an intuitive way. (If something that took 10s now takes 1s, that's “ten times as fast”, not “zero point nine times faster”.)
[1] Even latency changes are best described in terms of throughput.
how can lantency changes be described in terms of throughput? you can have completely different latencies with the same throughput due to different choices of pipelining, no?
The same way: If you change latency from 10s to 1s, it's ten times as fast in terms of latency (or 900% faster, if you will); earlier, you could do 0.1 things/second, and now you can do 1.0 thing/second. The only real difference between latency and throughput is whether you can overlap work instances or not, you can use the same language to talk about their changes.
You obviously cannot _calculate_ latency from throughput or vice versa (except of course that one bounds the other); they are different values. But both can use the (very simple, very intuitive) framework of “number of stuffs per time unit”.
Now where things become ugly is when you talk about “N% _slower_”, which is also useful but gets very quickly ambiguous and problematic when N is not close to zero.
> (If something that took 10s now takes 1s, that's “ten times as fast”, not “zero point nine times faster”.)
It still works with speed as the measurement (not as "zero point nine" but just "nine"), you just have to inverse the relationship. Going from 10s to 1s can still be described as "9 times faster" but it's because, less intuitively as you say, "faster" is comparing the 1s to the 10s (as in, "9(1s) plus 1s is 10s") rather than the other way around ("9(10s) plus 10s is 1s" is obviously false). This works because we know that 1s is less time than 10s; "faster" inverses the numerical relationship for time because increasing it inherently means "slower". Indeed, the difference between them is 9x where x = 1. And 10 to 0.1 is 99 times faster because 99x where x = 0.1 is 9.9 (measured by throughput, assuming only the rate changed, it's also 99x more things and 100x as many things).
(Not that I think you don't know all this, just nitpicking, really.)