Xiaofan Hu bom-d-van

Hi, I'm mcpower. I've done Advent of Code seriously for two years now in Python, placing 9th in 2018 and 12th in 2017. This year, I'm taking a break from aiming for the leaderboard - while it's fun and all, it is a bit stressful at times (the good kind of stress, though!). As such, I'd like to share a few tips for anyone wanting to aim for the leaderboard.

This is everything that worked for me. Your mileage may vary, though - don't take this as gospel, see what works for you.

Go fast

Go fast.

Genomics - A programmer's guide.

Andy Thomason is a Senior Programmer at Genomics PLC. He has been witing graphics systems, games and compilers since the '70s and specialises in code performance.

https://www.genomicsplc.com

Nginx TLS SNI routing, based on subdomain pattern

Nginx can be configured to route to a backend, based on the server's domain name, which is included in the SSL/TLS handshake (Server Name Indication, SNI).
This works for http upstream servers, but also for other protocols, that can be secured with TLS.

prerequisites

at least nginx 1.15.9 to use variables in ssl_certificate and ssl_certificate_key.
check nginx -V for the following:
```
...
TLS SNI support enabled
```

Virtual Networking on Linux

In the Linux Kernel, support for networking hardware and the methods to interact with these devices is standardized by the socket API:

                +----------------+
                |   Socket API   |
                +-------+--------+
                        |
User space              |

	// I created this to attach to https://stackoverflow.com/questions/60046598/ssh-through-bastion-host
	package main


	import (
	"flag"
	"fmt"
	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/agent"
	"log"

	class E(BaseException):
	def __new__(cls, args, *kwargs):
	return cls
	def a(): yield
	a().throw(E)

	define perl_stack
	set $end=my_perl->Icurstackinfo->si_cxix
	set $i=0
	while ($i<$end)
	printf "%d:%s\n", my_perl->Icurstackinfo->si_cxstack[$i].cx_u.cx_blk.blku_oldcop->cop_line, my_perl->Icurstackinfo->si_cxstack[$i].cx_u.cx_blk.blku_oldcop->cop_file
	set $i=$i+1
	end
	printf "%d:%s\n",my_perl->Icurcop->cop_line, my_perl->Icurcop->cop_file
	end

	(defstruct div-by-mul-constants
	;; Implement truncated integer by `divisor` with a fixed point
	;; approximation.
	(divisor 0 :type sb-ext:word
	:read-only t)
	;; The reciprocal is roughly multipler / 2^(W + shift),
	;; where W is the word width.
	(multiplier 0 :type sb-ext:word
	:read-only t)
	(shift 0 :type sb-ext:word

	#include <time.h> // Robert Nystrom
	#include <stdio.h> // @munificentbob
	#include <stdlib.h> // for Ginny
	#define r return // 2008-2019
	#define l(a, b, c, d) for (i y=a;y\
	<b; y++) for (int x = c; x < d; x++)
	typedef int i;const i H=40;const i W
	=80;i m[40][80];i g(i x){r rand()%x;
	}void cave(i s){i w=g(10)+5;i h=g(6)
	+3;i t=g(W-w-2)+1;i u=g(H-h-2)+1;l(u

	This is free and unencumbered software released into the public domain.

	Anyone is free to copy, modify, publish, use, compile, sell, or
	distribute this software, either in source code form or as a compiled
	binary, for any purpose, commercial or non-commercial, and by any
	means.

	In jurisdictions that recognize copyright laws, the author or authors
	of this software dedicate any and all copyright interest in the
	software to the public domain. We make this dedication for the benefit