json VS simdjson

git clone https://github.com/serde/json serde-json cd serde-json cargo build # build debug once to ensure dependencies are downloaded, so we aren't including download times in our test time cargo build --release

Can you point to some of these benchmarks? https://news.ycombinator.com/item?id=26934854 suggests that in at least one synthetic benchmark (with a 7.5KB protobuf message which expands to a 17KB JSON payload), protobuf parsing at 2GB/s would be comparable to JSON parsing at 5GB/s.

Meanwhile, simdjson's numbers (https://github.com/simdjson/simdjson/blob/master/doc/gbps.pn...) show a peak parsing speed of about 3GB/s depending on the workload. Of course, it's not clear you can compare these directly, since they were probably not run on systems with comparable specs. But it's not clear to me that there's a 5x difference.

Perhaps my experience differs because I'm used to seeing very large messages being passed around, but I'd be happy to reconsider. (Or maybe I should go all-in on Cap'n Proto.)

I intentionally said "more towards embarrassingly parallel" rather than "only embarrassingly parallel". I don't think there's a hard cutoff, but there is a qualitative difference. One example that springs to mind is https://github.com/simdjson/simdjson - afaik there's no similarly mature GPU-based JSON parsing.

It's also supported by simdjson [0] (which has a lot of language bindings [1]):

> Multithreaded processing of gigantic Newline-Delimited JSON (ndjson) and related formats at 3.5 GB/s

[0] https://simdjson.org/

[0] https://github.com/simdjson/simdjson?tab=readme-ov-file#bind...

String parsing is negligible compared to the speed of the DOM which is glacially slow: https://news.ycombinator.com/item?id=38835920

Come on, people, make an effort to learn how insanely fast computers are, and how insanely inefficient our software is.

String parsing can be done at gigabytes per second: https://github.com/simdjson/simdjson If you think that is the slowest operation in the browser, please find some resources that talk about what is actually happening in the browser?

Thanks for all the detailed information! That answers a bunch of my questions and the implementation of strlen is nice.

The instruction I was thinking of is pshufb. An example ‘weird’ use can be found for detecting white space in simdjson: https://github.com/simdjson/simdjson/blob/24b44309fb52c3e2c5...

This works as follows:

1. Observe that each ascii whitespace character ends with a different nibble.

2. Make some vector of 16 bytes which has the white space character whose final nibble is the index of the byte, or some other character with a different final nibble from the byte (eg first element is space =0x20, next could be eg 0xff but not 0xf1 as that ends in the same nibble as index)

3. For each block where you want to find white space, compute pcmpeqb(pshufb(whitespace, input), input). The rules of pshufb mean (a) non-ascii (ie bit 7 set) characters go to 0 so will compare false, (b) other characters are replaced with an element of whitespace according to their last nibble so will compare equal only if they are that whitespace character.

I’m not sure how easy it would be to do such tricks with vgather.vv. In particular, the length of the input doesn’t matter (could be longer) but the length of white space must be 16 bytes. I’m not sure how the whole vlen stuff interacts with tricks like this where you (a) require certain fixed lengths and (b) may have different lengths for tables and input vectors. (and indeed there might just be better ways, eg you could imagine an operation with a 256-bit register where you permute some vector of bytes by sign-extending the nth bit of the 256-bit register into the result where the input byte is n).

Additionally, if you like low level stuff, check out libfmt (https://github.com/fmtlib/fmt) - not a big project, not difficult to understand. Or something like simdjson (https://github.com/simdjson/simdjson).