Skip to content

Instantly share code, notes, and snippets.


Arseny Kapoulkine zeux

View GitHub Profile
zeux /
Last active Jun 1, 2021
How does clang 2.7 hold up in 2021?

A friend recently learned about Proebsting's law and mentioned it to me off hand. I knew about the law's existence but I never really asked myself - do I believe in it?

For people who aren't aware, Proebsting's law states:

Compiler Advances Double Computing Power Every 18 Years

Which is to say, if you upgrade your compiler every 18 years, you would expect on average your code to double in performance on the same hardware.

Let's C about this


State of Roblox graphics API across all platforms, with percentage deltas since EOY 2020. Updated June 11 2021.


API Share
Direct3D 11+ 90% (+1%)
Direct3D 10.1 6% (-1%)
Direct3D 10.0 4% (+0.5%)
zeux / builtin.lua
Created May 20, 2020
Roblox Luau type surface as of May 20, 2020
View builtin.lua
export type any=any
export type nil=nil
export type string=string
export type number=number
export type boolean=boolean
zeux / codecbench-clang.txt
Created Apr 25, 2020
codecbench: native gcc vs native clang vs v8 Wasm vs WAVM Wasm
View codecbench-clang.txt
source: vertex data 32064032 bytes, index data 24000000 bytes
pass 0: vertex data 18518385 bytes, index data 2332680 bytes
decode: vertex 9.31 ms (3.21 GB/sec), index 5.65 ms (3.95 GB/sec)
decode: vertex 9.43 ms (3.17 GB/sec), index 5.64 ms (3.96 GB/sec)
decode: vertex 9.44 ms (3.16 GB/sec), index 5.69 ms (3.93 GB/sec)
decode: vertex 9.47 ms (3.15 GB/sec), index 5.72 ms (3.91 GB/sec)
decode: vertex 9.50 ms (3.14 GB/sec), index 5.72 ms (3.91 GB/sec)
decode: vertex 9.36 ms (3.19 GB/sec), index 5.82 ms (3.84 GB/sec)
decode: vertex 9.57 ms (3.12 GB/sec), index 5.75 ms (3.89 GB/sec)
decode: vertex 9.47 ms (3.15 GB/sec), index 5.72 ms (3.91 GB/sec)
zeux / fixupsimd.js
Last active Apr 3, 2020
A SIMD opcode remapper for the impending Wasm SIMD instruction renumbering, written on stream
View fixupsimd.js
function fixupSimd(input) {
var data = new Uint8Array(input);
var read = 0;
var result = new Uint8Array(data.length * 2); // worst case: opcode renumbering changes 1-byte to 2-byte
var write = 0;
var readByte = function() {
if (read >= data.length) {
zeux /
Last active Jan 27, 2020
Writing down various options to extend meshoptimizer encoding API with format versioning


meshoptimizer currently ships with index and vertex codecs with the API along these lines:

size_t encode(destination, destination_capacity, source, source_size)
void decode(destination, destination_size, source, source_size)

The next version of meshoptimizer needs to make backwards incompatible changes to the encoding format to allow for better compression.


State of Roblox graphics API across all platforms, with percentage deltas since EOY 2019. Updated December 27 2020.


API Share
Direct3D 11+ 89% (+4%)
Direct3D 10.1 7% (-2%)
Direct3D 10.0 3.5% (-1.5%)
Direct3D 9 0.5% (-0.5%)
zeux / types.lua
Created Jan 18, 2020
Luau dumptypes output as of 1/17/2020
View types.lua
This file has been truncated, but you can view the full file.
type AdvancedDragger={
zeux / nbody.s
Last active Jan 2, 2020
luaujit: nbody.lua when compiled using experimental Luau JIT engine. All assembly snippets only show inner loop body. Variants: scalar - using type info, records and basic block compiler to generate much more efficient inner loop; vector - scalar but with scalars replaced with first-class 3-component vector
View nbody.s
# table type guard (memory safety)
cmp dword ptr [rdi + 12], 6
jne 1072 <.text+0x5ea>
# load array index and convert to integer (+ exactness check)
movsd xmm0, qword ptr [rdi + 256]
cvttsd2si eax, xmm0
cvtsi2sd xmm1, eax
ucomisd xmm1, xmm0
jne 1046 <.text+0x5ea>
# indices are 1-based; could remove this one with runtime changes
zeux / islandize-reuv.cpp
Last active Jun 25, 2019
Isolate UV islands and move each island to 0..1 range if possible; this reduces the total UV range of the mesh.
View islandize-reuv.cpp
unsigned int follow(std::vector<unsigned int>& ids, unsigned int v)
unsigned int nv = v;
while (ids[nv] != nv)
nv = ids[nv];
return ids[v] = nv;
size_t islandize(const std::vector<unsigned int>& indices, std::vector<unsigned int>& islands)