daniel-j-h

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <algorithm>
#include <fstream>
#include <functional>

#include "tbb/task_scheduler_init.h"
#include "tbb/blocked_range.h"

daniel-j-h

A plea for more tooling usage

Motivation

I tried to build Ceph with the Clang (3.4) compiler. The only issue preventing the build to finish was a "VLA of non-POD type" usage which I fixed here:

ceph/ceph#1768

daniel-j-h

#ifndef BLOCKING_QUEUE_H
#define BLOCKING_QUEUE_H

#include <list>
#include <mutex>
#include <condition_variable>
#include <iterator>


template <typename T>

daniel-j-h

Forcing Ceph into mapping all objects to a single PG

Motivation

Recently I was wondering how Ceph (i.e. Rados in particular) maps object to Placement Groups (PGs).

It basically works like the following:

pg = hash(object)

osd = crush(pg)

daniel-j-h

#!/usr/bin/env python2
# -*- coding: utf-8 -*-

# I used this in order to insert the preimages into a local ceph cluster,
# started in my ceph dev directory via src/vstart.sh. Adapt paths if needed.

import sys, os

srcdir = '/home/daniel/cn-work/ceph-dev/src'
pool = 'collisions'

daniel-j-h

#!/usr/bin/env python2
# -*- coding: utf-8 -*-

import sys, json
from collections import defaultdict
from scipy.stats import chisquare

# usage: ceph pg dump_json | ./check_distribution.py

if __name__ == '__main__':

daniel-j-h

#include <thread>
#include <utility>
#include <stdexcept>


// takes ownership of the thread
class scoped_thread {
  public:
    explicit scoped_thread(std::thread t_) : t(std::move(t_)) {
      if(!t.joinable()) throw std::logic_error{"no thread"};

daniel-j-h

#include <atomic>

class spinlock_mutex {
  public:
    spinlock_mutex() : flag(ATOMIC_FLAG_INIT) {}

    void lock() { while(flag.test_and_set(std::memory_order_acquire)); }
    void unlock() { flag.clear(std::memory_order_release); }

  private:

daniel-j-h

#!/usr/bin/env hy

(import [operator [eq]]
        [itertools [chain count]]
        [functools [partial reduce]])


(defn map-indexed [f coll]
  (map f (count) coll))

daniel-j-h

Introduction To PostGIS

• Blog https://daniel-j-h.github.io/post/gentle-introduction-postgis/
• PostGIS reference: http://postgis.net/docs/reference.html
• Postgres, esp. II.7 Queries http://www.postgresql.org/docs/9.4/interactive/index.html
• geojson.io: http://geojson.io/
• Mapbox: https://www.mapbox.com/
• CartoDB: http://cartodb.com/