On Tue, Nov 7, 2017 at 3:16 PM, Alan Donovan <adono...@google.com> wrote:
> On 7 November 2017 at 15:06, Ben Hoyt <benh...@gmail.com> wrote: > >> >> 2x as fast as CPython sounds pretty good to me -- nice! >>>> >>> > No, CPython is 2x as fast as Skylark in Go. It's implemented in C, so it > can do things that are sadly impossible in Go, like implement a threaded > bytecode interpreter. > Sorry, I actually grokked what you said but then repeated it incorrectly. I meant to say: half as fast as CPython sounds pretty good. I'm curious why you wrote the dict implementation from scratch >> (hashtable.go) instead of using Go maps as a base, and adding a secondary >> data structure (slice of keys?) to keep track of insertion order? I'm >> presuming there's a good technical reason, but at first glance it seems >> like it would be faster and simpler to use Go maps to start with. >> > > There are many reasons Go maps would not work. First, they do not allow > you to define the hash function and equivalence relation for keys. Skylark > considers 1.0 == 1, for instance, whereas Go does not; also. Second, Go > maps require that keys be comparable, but Skylark tuples are represented as > slices, for example. Third, Go maps have non-deterministic iteration order > whereas Skylark maps are ordered by insertion. You could maintain a > separate slice of keys for the iteration order, but at that point you're > halfway to building you're own hash table. > > Why should Go maps be faster? Go's map is implemented in Go. There's no > reason a different implementation should be equally fast, or perhaps even > faster. The basic design of the Skylark-in-Go hash table is actually very > similar to Go's map. > Thanks for the thorough response, that's really helpful. I hadn't yet realized that Go maps don't allow you to define the hash / equality functions. And good point about Go's map also being implemented in Go too. I'm a lot more familiar with CPython internals, and was kind of assuming Go maps were written in C+asm, but it looks like the entire runtime is written in Go now (with a bit of assembly). -Ben -- 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. For more options, visit https://groups.google.com/d/optout.
