nevack

This gist is currenctly archived.

Please refer to previous revisions if you know what to do.

The patch proposed was merged into kernel in 5.8 release, but no longer working as of linux 5.11

erincandescent

Foreward

This document was originally written several years ago. At the time I was working as an execution core verification engineer at Arm. The following points are coloured heavily by working in and around the execution cores of various processors. Apply a pinch of salt; points contain varying degrees of opinion.

It is still my opinion that RISC-V could be much better designed; though I will also say that if I was building a 32 or 64-bit CPU today I'd likely implement the architecture to benefit from the existing tooling.

Mostly based upon the RISC-V ISA spec v2.0. Some updates have been made for v2.2

Original Foreword: Some Opinion

The RISC-V ISA has pursued minimalism to a fault. There is a large emphasis on minimizing instruction count, normalizing encoding, etc. This pursuit of minimalism has resulted in false orthogonalities (such as reusing the same instruction for branches, calls and returns) and a requirement for superfluous instructions which impacts code density both in terms of size and

rygorous

why doesn't radfft support AVX on PC?

So there's two separate issues here: using instructions added in AVX and using 256-bit wide vectors. The former turns out to be much easier than the latter for our use case.

Problem number 1 was that you positively need to put AVX code in a separate file with different compiler settings (/arch:AVX for VC++, -mavx for GCC/Clang) that make all SSE code emitted also use VEX encoding, and at the time radfft was written there was no way in CDep to set compiler flags for just one file, just for the overall build.

[There's the GCC "target" annotations on individual funcs, which in principle fix this, but I ran into nasty problems with this for several compiler versions, and VC++ has no equivalent, so we're not currently using that and just sticking with different compilation units.]

The other issue is to do with CPU power management.

jFransham

Achieving warp speed with Rust

Contents:

• Number one optimization tip: don't
• Never optimize blindly
• Don't bother optimizing one-time costs
• Improve your algorithms
• CPU architecture primer
• Keep as much as possible in cache
• Keep as much as possible in registers

simonw

$ wget -e robots=off -r -np 'http://example.com/folder/'

• -e robots=off causes it to ignore robots.txt for that domain
• -r makes it recursive
• -np = no parents, so it doesn't follow links up to the parent folder

MichaelPote

#
# Himawari-8 Downloader
#
#
#
# This script will scrape the latest image from the Himawari-8 satellite, recombining the tiled image,
# converting it to a JPG which is saved in My Pictures\Himawari\ and then set as the desktop background.
#
# http://himawari8.nict.go.jp/himawari8-image.htm
#

lelandbatey

Description

This simple script will take a picture of a whiteboard and use parts of the ImageMagick library with sane defaults to clean it up tremendously.

The script is here:

#!/bin/bash
convert "$1" -morphology Convolve DoG:15,100,0 -negate -normalize -blur 0x1 -channel RBG -level 60%,91%,0.1 "$2"

Results

rofl0r

#define _XOPEN_SOURCE 700
#include <signal.h>
#include <unistd.h>

int main()
{
	sigset_t set;
	int status;

	if (getpid() != 1) return 1;

quchen

13:15 <xQuasar>      | HASKELL IS FOR FUCKIN FAGGOTS. YOU'RE ALL A BUNCH OF 
                     | FUCKIN PUSSIES
13:15 <xQuasar>      | JAVASCRIPT FOR LIFE FAGS
13:16 <luite>        | hello
13:16 <ChongLi>      | somebody has a mental illness!
13:16 <merijn>       | Wow...I suddenly see the error of my ways and feel 
                     | compelled to write Node.js!
13:16 <genisage>     | hi
13:16 <luite>        | you might be pleased to learn that you can compile 
                     | haskell to javascript now