zeeshanlakhani

Erlang Tracing: more than you wanted to know

Rough Outline

• What can be traced?
• How can trace events be specified?
• "match specifications": twisty passages, all alike
• WTF, can I just use DTrace and drink my coffee/beer/whisky in peace?
• Trace delivery mechanisms: pick one of two

zeeshanlakhani

Latency Comparison Numbers
--------------------------
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
Send 1K bytes over 1 Gbps network        10,000   ns    0.01 ms
Read 4K randomly from SSD*              150,000   ns    0.15 ms

zeeshanlakhani

# List of all the valid pdf URLs ever posted to the #Clojure IRC channel.
#
# Many of them are interesting CS papers others are not that useful. What I've done:
#
# 1. crawled an IRC history archive for the channel
# 2. extract pdf list in a file with: grep -riIohE 'https?://[^[:space:]]+pdf' * > pdf-links.txt
# 3. remove dupes: cat pdf-links.txt | sort | uniq > pdf-links-uniq.txt
# 4. filter only HTTP 200: cat pdf-links-uniq.txt | xargs curl -o /dev/null --connect-timeout 2 --silent --head --write-out '%{http_code} %{url_effective}\n' | grep "^200" > valid-pdf-links.txt
# 
# Now your choice to download them all or not. If you want, use: cat valid-pdf-links.txt | awk '{print $2}' | xargs wget

zeeshanlakhani

Description

This simple script will take a picture of a whiteboard and use parts of the ImageMagick library with sane defaults to clean it up tremendously.

The script is here:

#!/bin/bash
convert "$1" -morphology Convolve DoG:15,100,0 -negate -normalize -blur 0x1 -channel RBG -level 60%,91%,0.1 "$2"

Results

zeeshanlakhani

USING: kernel math sequences ;
IN: euler1

: multiple-of ( x y -- z ) mod zero? ;

: euler1 ( x -- y )
    1 - iota [ 1 + ] map
    [ dup [ 3 multiple-of ] [ 5 multiple-of ] bi or [ ] [ drop 0 ] if ]
    map
    sum

zeeshanlakhani

four primitives: run*, ==, conde, fresh

(run* (q)
  (== q #t))

; for what values of q is q equal to true?

answer: q must also be #t, so
'(#t)    ; answer comes back in a list

zeeshanlakhani

# time
# ====

macro time(ex)
    quote
        local t0 = time_ns()
        local val = $(esc(ex))
        local t1 = time_ns()
        println("elapsed time: ", (t1-t0)/1e9, " seconds")
        val

zeeshanlakhani

(ns markerbot.core
 (:require [taoensso.timbre :as log]
           [clojure.data.json :as json]
           [clojure.string :as s]
           [clj-http.client :as client])
  (:import (java.net Socket)
           (java.io PrintWriter InputStreamReader BufferedReader))
  (:gen-class))

;; marksy

zeeshanlakhani

# config/environments/production.rb

# We're on Heroku, just output straight to STDOUT
# This is required because we're using Unicorn: https://github.com/ryanb/cancan/issues/511#issuecomment-3643266
config.logger = Logger.new(STDOUT)
config.logger.level = Logger.const_get(ENV['LOG_LEVEL'] ? ENV['LOG_LEVEL'].upcase : 'INFO')

zeeshanlakhani

use Rack::Static, :urls => ["/stylesheets", "/images"], :root => "public"
run lambda { |env| [200, { 'Content-Type' => 'text/html', 'Cache-Control' => 'public, max-age=86400' }, File.open('public/index.html', File::RDONLY)] }