Joshua Hansen joshes

Direct links to free Springer maths books (pdf versions)

duplicates = multiple editions

A Classical Introduction to Modern Number Theory,Kenneth IrelandMichael Rosen

A Course in Arithmetic,Jean-Pierre Serre

AWS CLI Cheatsheet

http://docs.aws.amazon.com/IAM/latest/UserGuide/best-practices.html https://www.youtube.com/watch?v=_wiGpBQGCjU

Setup

Each of these commands will run an ad hoc http static server in your current (or specified) directory, available at http://localhost:8000. Use this power wisely.

Discussion on reddit.

Python 2.x

$ python -m SimpleHTTPServer 8000

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

	DELIMITER $$
	CREATE FUNCTION `haversine` (lat1 DECIMAL(8,6), lng1 DECIMAL(8,6), lat2 DECIMAL(8,6), lng2 DECIMAL(8,6)) RETURNS DECIMAL(8,6)
	BEGIN
	DECLARE R INT;
	DECLARE dLat DECIMAL(30,15);
	DECLARE dLng DECIMAL(30,15);
	DECLARE a1 DECIMAL(30,15);
	DECLARE a2 DECIMAL(30,15);
	DECLARE a DECIMAL(30,15);
	DECLARE c DECIMAL(30,15);

	# https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/mon-scripts.html
	#.ebextensions/01-memorymon.config

	packages:
	yum:
	perl-Switch: []
	perl-DateTime: []
	perl-Sys-Syslog: []
	perl-LWP-Protocol-https: []
	perl-Digest-SHA.x86_64: []

	#!/bin/bash
	###
	### my-script — does one thing well
	###
	### Usage:
	### my-script <input> <output>
	###
	### Options:
	### <input> Input file to read.
	### <output> Output file to write. Use '-' for stdout.

	# Pass the env-vars to MYCOMMAND
	eval $(egrep -v '^#' .env \| xargs) MYCOMMAND
	# … or ...
	# Export the vars in .env into your shell:
	export $(egrep -v '^#' .env \| xargs)