> Except that we can't measure the performance of a specification. > We can only measure the performance of entire implementations. > I can make an implementation that conforms to PEP 626 that is slower > than master, or I can make one that's faster :) > It doesn't change the value of the PEP itself.
Oh, I see now where the confusion is. Regarding the benchmarks, unless is catastrophically worse and there is no way to make it competitive, the PEP acceptance is not conditional to the specific result of the benchmarks: my request is just to *have* a benchmark on the implementation :) On Thu, 29 Oct 2020 at 13:29, Mark Shannon <m...@hotpy.org> wrote: > Hi Pablo, > > On 29/10/2020 11:08 am, Pablo Galindo Salgado wrote: > > > The new semantics may well result in some slowdowns. That's stated in > > the PEP.I don't think I can reliably isolate the effects of the (very > > slight) > > change in the behavior of f_lineno. > > > > Ok, then let's make at least we measure the general slowdowns. > > Except that we can't measure the performance of a specification. > We can only measure the performance of entire implementations. > > I can make an implementation that conforms to PEP 626 that is slower > than master, or I can make one that's faster :) > It doesn't change the value of the PEP itself. > > Let me give you a toy example. > > def f(): > while 1: > body() > > 3.9 compiles this to: > > (The trailing, implicit return has been stripped for clarity) > > 3 >> 0 LOAD_GLOBAL 0 (body) > 2 CALL_FUNCTION 0 > 4 POP_TOP > 6 JUMP_ABSOLUTE 0 > > A naive implementation that conforms to PEP 626 would this compile to: > > 2 >> 0 NOP > 3 2 LOAD_GLOBAL 0 (body) > 4 CALL_FUNCTION 0 > 6 POP_TOP > 8 JUMP_ABSOLUTE 0 > > But a better implementation could produce this: > > 2 0 NOP > 3 >> 2 LOAD_GLOBAL 0 (body) > 4 CALL_FUNCTION 0 > 6 POP_TOP > 2 8 JUMP_ABSOLUTE 2 > > Which has the same bytecodes as 3.9 in the loop, and has the correct > line numbers. > > Cheers, > Mark. >
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