Unrelated to this specific post I’m such a fan of Zed. It’s the first feature complete text editor in recent memory that I’ve truly enjoyed using (i.e. it stays out of the way, is really fast, feels well engineered). I’m coming to Zed after years of Emacs which I still have love for but no longer feels like a competitive piece of software (it does not take full advantage of how good computers are today, e.g. gpu rendering or multicore). I really hope Zed stays a fast and lightweight text editor instead of becoming some bloated growth-at-all-cost VC ware (not that they’ve exhibited any signs of that happening). I’d also happily pay for Zed without a subscription based thing for access to LLM features (which I do not use).
Why does Emacs need that though? I hear people say this all the time and I don't get it. Multicore kind of works against the structure that Emacs touts as a feature. And GPU rendering? In many applications, I totally agree with these complaints. But it's a text editor.
I tried Zed myself, and it's good. But it doesn't dethrone Emacs (for me personally).
Long time emacs user here (+20 years, yikes). I've used it on all kinds of computers during this time. Even a relatively modest computer from 2024 is an absolute beast compared to something from the year 2000.
With that said, there are text editing operations that can cause it to grind to a complete halt, especially working with large files (or very long lines). And it shouldn't, you know? I think emacs users sort of internalize which operations they should avoid. It's kind of ridiculous to have to do that in a text editor with the massive amounts of compute that our computers have today.
I have consistent issues with emacs locking up when executing network requests. I'm sure there's a specific bug that could be hunted down and addressed, but this sort of thing shouldn't happen much in an editor that's multicore by default.
I'm not trying to dismiss emacs' reasoning, of course, but I can understand being disgruntled with it.
The actual rendering I've been quite please by, though!
Most new TTY projects use GPUs for that reason
The are serious about local vs. remote vs. shared. They are serious about hardware acceleration because they care about users who type fast and edit big files. They care about real computer science on how to push the current hardware to serve the user, rather than treating the hardware as a crutch to give the user a slightly worse experience at a fraction of the development cost. They care about code highlighting the snippets on their blog like very similar to the default Zed theme.
These are cool, serious people. If they give me emacs key bindings with full paredit-everywhere, I might switch my daily driver.
And this is about using modern SIMD-style stuff, branch less stuff, Lemire stuff in a modern and relevant context. Other commenters have pointed out that you can do the mask or popcount better with intrinsically, and yeah, but they probably know that, and B. They got the massive win, the remaining factor of K on the pop count is coming.
Long Zed.
You don't need information about the position of newlines in all the chunks located before the one your offset lands on
> // Parallel bit count intermediates
> let a = v - ((v >> 1) & (u64::MAX / 3));
> let b = (a & (u64::MAX / 5)) + ((a >> 2) & (u64::MAX / 5));
> let c = (b + (b >> 4)) & (u64::MAX / 0x11);
> let d = (c + (c >> 8)) & (u64::MAX / 0x101);
Bitstring rank/select is a well-known problem, and the BMI and non-BMI (Hacker's Delight) versions are available as a reference.
I've been saying this a lot recently, that CPU's are powerful 1-bit vector machines!
I know that they have some recordings from their coding session, but I am looking for something more overall.
> filter: blur(1px);
Wonderful styling!
aa -> -> bb -> -> bb
It only takes up two spaces, after all
On processors with BMI2 the whole algorithm reduces to a PDEP as mentioned in another comment, but if you don't have that this is pretty much the best you can do (unless you use lookup tables but those have pros and cons).
The above code is completely source- and binary-portable and reasonably fast -- certainly faster than naively looping through the bits, and within a small constant factor of a CPU POPCOUNT instruction.
And the compiler is not required to lower it to a single instruction. It will if the target architecture is specified appropriately, but there's nothing that says it has to explode if it can't. In fact, by doing it this way, the compiler is actually more free to generate code in a way that's optimal for the architecture in all cases, because all the implementation details are hidden e.g. loads of large constants may be avoided if the compiler is allowed to choose the exact implementation, while using the portable version may tie its hands more depending on how it's feeling on that day. Here's __builtin_popcount working just fine while targeting a ~20yo architecture without native support for SSE4.2; it can generate this code knowing what the proper instructions and schedules are: https://godbolt.org/z/ra7n5T5f3
The moral here is that the primitives are there for you to use. Just use them and save yourself and your would-be code reviewer's time.
Also, pretty much every compiler for a very long time has supported __builtin_popcount or equivalent.
Clang supports __builtin_popcount() too. And MSVC has __popcnt().
However, as someone already mentioned, this is not equivalent to a pair of popcounts.
On the Intel side, pdep has been fast since its release with the Haswell in 2013, so pretty much everyone using Intel should be fine in this regard.
> If you called rope.offset_to_point(7234), the Rope would traverse its SumTree to find the Chunk that contains offset 7234 and then, on that Chunk, it would call offset_to_point again.
And here:
> while the Rope can get us to the right Chunk in O(log(n))
I would guess that each node of the SumTree includes the number of newlines of all the chunks before it.
Long line handling has greatly improved in emacs-29. Multi-megabyte lines are not a problem anymore.
** Emacs is now capable of editing files with very long lines.
The display of long lines has been optimized, and Emacs should no
longer choke when a buffer on display contains long lines. The
variable 'long-line-threshold' controls whether and when these display
optimizations are in effect.
A companion variable 'large-hscroll-threshold' controls when another
set of display optimizations are in effect, which are aimed
specifically at speeding up display of long lines that are truncated
on display.64-bit ARM's actually has a very peculiar encoding of immediates to arithmetic instructions. It supports only recurring bit patterns such as used by this algorithm. For example "add x2, x3, #3333333333333333" is encoded as one four-byte instruction.
It does have this: https://developer.arm.com/documentation/ddi0596/2021-09/SIMD...
And GCC happily uses it https://godbolt.org/z/dTW46f9Kf
I use Emacs GUI (outside of the terminal) and comparing performance for rending to something like Zed or Sublime is definitely noticeable. It’s great that Emacs is so resource efficient but sometimes I wish it used more of my beefy computer(s).
Like I said I still love Emacs and it’s okay for it to make a different set of trade-offs. I honestly didn’t think I’d ever switch editors but here we are!
Installing packages does not need to block either, there is no architectural limitation here. The Elpaca package manager for Emacs provides async, parallel package updates. Loading packages into the Lisp image will block though, there's no way around that.
The other big source of input lag is garbage collection, and there are some ongoing efforts to use the MPS library in Emacs for a copying, concurrent GC. This is a big change and I don't know if this experiment will go anywhere, but Eli Zaretskii and co are trying.
As for LSP, other than the Nim langserver, I've been quite satisfied with Eglot's performance. I'm curious what your setup is like. To be fair, I'm running a highly customized Doom Emacs config, so it's possible I inherited some non-vanilla optimizations I'm not aware of.
Parallelism trivially enables concurrency. The lack of parallelism magnifies the issues emacs has with concurrency.