wdv4758h

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

wdv4758h

CUSTOM GAME ENGINES: A Small Study

A couple of weeks ago I played (and finished) A Plague Tale, a game by Asobo Studio. I was really captivated by the game, not only by the beautiful graphics but also by the story and the locations in the game. I decided to investigate a bit about the game tech and I was surprised to see it was developed with a custom engine by a relatively small studio. I know there are some companies using custom engines but it's very difficult to find a detailed market study with that kind of information curated and updated. So this article.

Nowadays lots of companies choose engines like Unreal or Unity for their games (or that's what lot of people think) because d

wdv4758h

taskA:
	@echo "this is task A"
	@sleep 1
	@echo "end task A"

taskB: taskA
	@echo "this is task B"
	@sleep 3
	@echo "end task B"

wdv4758h

What is the Strict Aliasing Rule and Why do we care?

(OR Type Punning, Undefined Behavior and Alignment, Oh My!)

What is strict aliasing? First we will describe what is aliasing and then we can learn what being strict about it means.

In C and C++ aliasing has to do with what expression types we are allowed to access stored values through. In both C and C++ the standard specifies which expression types are allowed to alias which types. The compiler and optimizer are allowed to assume we follow the aliasing rules strictly, hence the term strict aliasing rule. If we attempt to access a value using a type not allowed it is classified as undefined behavior(UB). Once we have undefined behavior all bets are off, the results of our program are no longer reliable.

Unfortunately with strict aliasing violations, we will often obtain the results we expect, leaving the possibility the a future version of a compiler with a new optimization will break code we th

wdv4758h

#!/usr/bin/env python3

###################################################################
#  cpuinfo - Get information about CPU
#
#      License: BSD
#      Author:  Pearu Peterson <pearu@cens.ioc.ee>
#
#  See LICENSES/cpuinfo.txt for details about copyright and
#  rights to use.

wdv4758h

Looking into the Future

futures-rs is the library which will hopefully become a shared foundation for everything async in Rust. However it's already become renowned for having a steep learning curve, even for experienced Rustaceans.

I think one of the best ways to get comfortable with using a library is to look at how it works internally: often API design can seem bizarre or impenetrable and it's only when you put yourself in the shoes of the library author that you can really understand why it was designed that way.

In this post I'll try to put down on "paper" my understanding of how futures work and I'll aim to do it in a visual way. I'm going to assume you're already somewhat familiar with Rust and why futures are a useful tool to have at one's disposal.

For most of this post I'll be talking about how things work today (as of September 2017). At the end I'll touch on what's being proposed next and also make a case for some of the changes I'd like to see.

If you're interested in learning more ab

wdv4758h

Keybase proof

I hereby claim:

• I am wdv4758h on github.
• I am wdv4758h (https://keybase.io/wdv4758h) on keybase.
• I have a public key ASC1uSowA-ZoCor0SReI52TbMZReNsxxISfKug-U0YYALgo

To claim this, I am signing this object:

wdv4758h

#[derive(Debug, PartialEq)]
pub enum SimliarityError {
    DifferentLength
}

pub type HammingResult = Result<usize, SimliarityError>;

/// trait for Hamming Distance
pub trait Hamming {
    fn hamming(&self, rhs: &Self) -> HammingResult;

wdv4758h

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

wdv4758h

許邱翔, Chiu-Hsiang Hsu

Email

wdv4758h@gmail.com

GitHub

https://github.com/wdv4758h/

Notes

https://github.com/wdv4758h/notes/

Blog

https://wdv4758h.github.io/

Table of Contents