Mayuresh Waykole mayureshwaykole

Code is clean if it can be understood easily – by everyone on the team. Clean code can be read and enhanced by a developer other than its original author. With understandability comes readability, changeability, extensibility and maintainability.

General rules

Follow standard conventions.
Keep it simple stupid. Simpler is always better. Reduce complexity as much as possible.
Boy scout rule. Leave the campground cleaner than you found it.
Always find root cause. Always look for the root cause of a problem.

Design rules

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

Network

connectivity

[]telnet from source to destination. If connection refused, no connectivity []traceroute -s source_ip -p port dest_host

Which ports are listening netstat -plnt

	# From https://web.archive.org/web/20250327175824/https://blog.gitbutler.com/how-git-core-devs-configure-git/

	[column]
	ui = auto
	[branch]
	sort = -committerdate
	[tag]
	sort = version:refname
	[init]
	defaultBranch = main

	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

	#!/bin/bash


	if [ -z "$1" ]; then
	echo
	echo usage: $0 network-interface
	echo
	echo e.g. $0 eth0
	echo
	echo shows packets-per-second

	valgrind --leak-check=full \
	--show-leak-kinds=all \
	--track-origins=yes \
	--log-file=valgrind-out.txt \
	--num-callers=20 \
	./binary

	To find out where disk space is being used:

	1. Get to the root of your machine by running cd /
	2. Run sudo du -h --max-depth=1
	3. Note which directories are using a lot of disk space.
	4. cd into one of the big directories.
	5. Run ls -l to see which files are using a lot of space. Delete any you don’t need.
	6. Repeat steps 2 to 5.

	echo '/tmp/core.%h.%e.%t' > /proc/sys/kernel/core_pattern
	ulimit -c unlimited

	if using in docker, run with --privileged

	/*
	* A simple example of json string parsing with json-c.
	*
	* clang -Wall -g -I/usr/include/json-c/ -o json_parser json_parser.c -ljson-c
	*/
	#include <json.h>
	#include <stdio.h>

	int main() {
	struct json_object *jobj;