headius

Algorithm

1. A secret byte you want to read is stored at inaccessible memory location priv_mem.
2. The sender triggers an access exception by attempting to read priv_mem.
3. Due to CPU optimization (out-of-order execution), the load of secret from priv_mem and the use of its value in (4) and (5) below may execute before the exception is triggered.
4. Calculate an offset into a known array probe by multiplying secret by the width of a cache line (or whatever block size the CPU typically fetches, like a 4096-byte page). This guarantees each of those 256 possible offsets will cache separately.
5. Load probe[offset], which causes the CPU to cache exactly one chunk of of our array, populating one cache line.
6. The exception finally triggers, clearing the modified registers...but cached data is not excised.
7. Iterate over all 256 offsets into probe to find out which one loads fast. You've determined the value of secret.

sasa1977

# http://adventofcode.com/2017/day/1

defmodule Day1 do
  def sum1(digits), do:
    digits
    |> Stream.concat(Enum.take(digits, 1))
    |> Stream.chunk_every(2, 1, :discard)
    |> Stream.filter(&match?([el, el], &1))
    |> Stream.map(&hd(&1))
    |> Enum.sum()

danielberkompas

defmodule MyApp.Scheduler do
  @moduledoc """
  Schedules a Mix task to be run at a given interval in milliseconds.

  ## Options

  - `:task`: The name of the Mix task to run.
  - `:args`: A list of arguments to pass to the Mix task's `run/1` function.
  - `:interval`: The time interval in millisconds to rerun the task.

MohamedAlaa

tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname