Offline MySQL migration

http://serverfault.com/questions/659048/can-i-copy-the-entire-var-lib-mysql-folder-to-a-different-server-mysql-vs-mar

C# performance notes

• for v.s foreach
  1. for loops on List are a bit more than 2 times cheaper than foreach loops on List.
  2. Looping on Array is around 2 times cheaper than looping on List.
  3. As a consequence, looping on Array using for is 5 times cheaper than looping on List using foreach.
  4. LinkedList only allows foreach loops, as it would take quadratic time to loop a LinkedList through indices.
  5. Looping overheads: for < foreach; Array ~ List < ArrayList < LinkedList
• Everything stored in an ArrayList is an object. So be careful of the boxing/unboxing overhead.
• String concatenation overheads are negligible outside loops. 

Fill and sign PDF forms online

http://www.pdfescape.com/

Symbolic executions

Symbolic Execution Tutorial

Symbolic Execution for Software Testing: Three Decades Later

Graph logics

The paper Simulate transitive closure using FO logic uses first-order theorem provers to prove transitive closures of certain binary predicates.

Courcelle's theorem

React.js tips

http://blog.revathskumar.com/2015/08/reactjs-things-i-learned-after-building-first-app.html

Converts videos to WebM with aconv/ffmpeg

Using aconv:
http://daniemon.com/blog/how-to-convert-videos-to-webm-with-ffmpeg/

Using ffmpeg:
http://trac.ffmpeg.org/wiki/Encode/VP8

Example code:

ffmpeg -i $INPUT -c:v libvpx -crf 4 -b:v 10M -c:a libvorbis $OUTPUT

The above command converts the input file to webm with a variable bitrate in a constant quality mode, which ensures that every frame achieve a certain quality level. In this command, -b:v 10M sets the maximum allowed bitrate to 10 MBit/s and -crf 4 sets the constant quality to 4 (best quality).