franckverrot

var 0..9: POS_1;
var 0..9: POS_2;
var 0..9: POS_3;


constraint (
   % 682 one correct and well placed
   (
      (POS_1 == 6 /\ (not (POS_2 in {8, 2})) /\ (not (POS_3 in {8, 2})))
   \/ (POS_2 == 8 /\ (not (POS_1 in {6, 2})) /\ (not (POS_3 in {6, 2})))

franckverrot

solution(POS_1, POS_2, POS_3) :-
  member(POS_1, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
  member(POS_2, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
  member(POS_3, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),

  /* 682 one correct and well placed */
  ( POS_1 = 6; POS_2 = 8; POS_3 = 2),

  /* 614 one correct not well placed */
  (

franckverrot

/*
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 */

#include <arpa/inet.h>
#include <linux/if_packet.h>
#include <stdio.h>

franckverrot

Zero knowledge databases

The idea

The idea is to provide a database as a service to end users in such a way that no one except the user herself can access the data, not even the hosting provider or the database administrator.

Advantages

• A privacy- and/or security-conscious user will have more trust in such a setup.
• The service provider cannot be coerced to release the data they were trusted with, and he cannot be held responsible for the content he is storing.

franckverrot

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

franckverrot

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

franckverrot

require 'fiddle'
require 'minitest/autorun'

class RubyVM
  class InstructionSequence
    address = Fiddle::Handle::DEFAULT['rb_iseq_load']
    func = Fiddle::Function.new(address, [Fiddle::TYPE_VOIDP] * 3, Fiddle::TYPE_VOIDP)

    define_singleton_method(:load) do |data, parent = nil, opt = nil|
      func.call(Fiddle.dlwrap(data), parent, opt).to_value

franckverrot

Install Dependencies

npm install --save jquery popper.js tether bootstrap@4.0.0-beta font-awesome // popper.js for bootstrap 4 dependency

Copy font-awesome fonts to assets/static/fonts folder

cp -r assets/node_modules/font-awesome/fonts to assets/static

franckverrot

defmodule HttpRequester do
  use GenServer

  def start_link(_) do
    GenServer.start_link(__MODULE__, nil, [])
  end

  def fetch(server, url) do
    # Don't use cast: http://blog.elixirsips.com/2014/07/16/errata-dont-use-cast-in-a-poolboy-transaction/
    timeout_ms = 10_000

franckverrot

These are the Kickstarter Engineering and Data role definitions for both teams.

Technical	Data	People
Junior Software Engineer
Software Engineer	Data Analyst
Senior Software Engineer	Data Scientist	Engineering Manager
Staff Engineer	VP of Data	Engineering Director
Principal Engineer		CTO