riscv-v-spec
simdjson
riscv-v-spec | simdjson | |
---|---|---|
43 | 65 | |
858 | 18,386 | |
- | 0.5% | |
6.0 | 9.2 | |
about 2 months ago | 9 days ago | |
Assembly | C++ | |
Creative Commons Attribution 4.0 | Apache License 2.0 |
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riscv-v-spec
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Scaleway launches RISC-V servers
Here are some resources I can recommend:
RVV spec (also look at the examples in the repo): https://github.com/riscv/riscv-v-spec/blob/master/v-spec.ado...
RVV intrinsics viewer: https://dzaima.github.io/intrinsics-viewer
Tutorial: RISC-V Vector Extension Demystified (3 hour video going over every instruction): https://youtu.be/oTaOd8qr53U
RISC-V Vector extension in a nutshell: https://fprox.substack.com/p/risc-v-vector-extension-in-a-nu...
If you want to see a more complex example/real world application, then you might also be ibterested ib my article about vectorizing unicode conversions: https://camel-cdr.github.io/rvv-bench-results/articles/vecto...
In terms of development I'd recommend using qemu and a cross compiler, or if you want hardware try to get the kendryte k230 (currently the only sbc with rvv 1.0 support) or wait a bit for better hardware (BPI-F3 and sg2380 should release this year).
- Cray-1 performance vs. modern CPUs
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x86 vs ARM; Vector and Matrix Extensions; How do they compare?
And this isn't just some theoretical or something unlikely to happen - the official spec already contains such a bug. If the writers of the spec can't get things right, even with the small amount of code in the spec, I don't have high hopes that less informed programmers will. RVV being absurdly complicated (IMO, compared to SVE2 and AVX10) doesn't help its cause here.
- riscv64 is now an official Debian architecture (rebootstrap in progress)
- Vector vs SIMD
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LLVM's libc Gets Much Faster memcpy For RISC-V
Will the reference one actually be the most optimal one on future hardware?
- Is there any good place to find a copy-paste-able quick reference on RISC-V extensions? Particularly for the vector extension
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Building a toolchain suitable for compiling V extension code
I'll do a deep dive into the https://gms.tf/riscv-vector.html#getting-started tutorial, and probably pop the proverbial stack and just study RVV 0.7.1 on its own (using https://github.com/riscv/riscv-v-spec/releases/tag/0.7.1).
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A weird idea for using RV32E on a RV32I core - multithreaded microcontrollers?
I see your point. You can file a request for it at https://github.com/riscv/riscv-v-spec/issues if you want to pitch it to the relevant ISA bodies. The bar for implementing it pretty high.
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Examining the Top Five Fallacies About RISC-V
It's not "unusual"; using data registers for mask is a valid tradeoff especially for low-end implementations, whereas higher-end architectures can easily use shadow registers. Discussed in depth at https://github.com/riscv/riscv-v-spec/issues/811
simdjson
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Tips on adding JSON output to your command line utility. (2021)
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...
- 1BRC Merykitty's Magic SWAR: 8 Lines of Code Explained in 3k Words
- Training great LLMs from ground zero in the wilderness as a startup
- simdjson: Parsing Gigabytes of JSON per Second
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Use any web browser as GUI, with Zig in the back end and HTML5 in the front end
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?
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Cray-1 performance vs. modern CPUs
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).
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Codebases to read
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).
- Simdjson: Parsing Gigabytes of JSON per Second
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Building a high performance JSON parser
Everything you said is totally reasonable. I'm a big fan of napkin math and theoretical upper bounds on performance.
simdjson (https://github.com/simdjson/simdjson) claims to fully parse JSON on the order of 3 GB/sec. Which is faster than OP's Go whitespace parsing! These tests are running on different hardware so it's not apples-to-apples.
The phrase "cannot go faster than this" is just begging for a "well ackshully". Which I hate to do. But the fact that there is an existence proof of Problem A running faster in C++ SIMD than OP's Probably B scalar Go is quite interesting and worth calling out imho. But I admit it doesn't change the rest of the post.
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New package : lspce - a simple LSP Client for Emacs
I have same question as /u/JDRiverRun : how do you deal with JSON, do you parse json on Rust side or on Emacs side. I see that you are requiring json.el in your lspce.el, but I haven't looked through entire file carefully. If you parse on Rust side, do you use simdjson (there are at least two Rust bindings to it)? If yes, what are your impressions, experiences compared to more "standard" json library?
What are some alternatives?
riscv-p-spec - RISC-V Packed SIMD Extension
RapidJSON - A fast JSON parser/generator for C++ with both SAX/DOM style API
highway - Performance-portable, length-agnostic SIMD with runtime dispatch
jsoniter - jsoniter (json-iterator) is fast and flexible JSON parser available in Java and Go
highway - Highway - A Modern Javascript Transitions Manager
json - JSON for Modern C++
riscv-bitmanip - Working draft of the proposed RISC-V Bitmanipulation extension
json-schema-validator - JSON schema validator for JSON for Modern C++
vroom - VRoom! RISC-V CPU
JsonCpp - A C++ library for interacting with JSON.
learn-fpga - Learning FPGA, yosys, nextpnr, and RISC-V
json - A C++11 library for parsing and serializing JSON to and from a DOM container in memory.