Isak Sky isaksky

F# Advent 2016 (English) - December 10 - Implementing a persistent hash map.

This blog created for F# Advent 2016 (English)

Changelog

2016-12-10
New performance test - Anthony Lloyd (@AnthonyLloyd) suggested that I compare against Prime.Vmap.

On the topic of data locality and performance

It is well-known that a hard disk has a long delay from that we request the data to that we get the data. Usually we measure the hard disk latency in milliseconds which is an eternity for a CPU. The bandwidth of a hard disk is decent good as SSD:s today can reach 1 GiB/second.

What is less known is that RAM has the same characteristics, bad latency with good bandwidth.

You can measure RAM latency and badndwidth using Intel® Memory Latency Checker. On my machine the RAM latency under semi-high load is ~120 ns (The 3r:1w bandwidth is 16GiB/second). This means that the CPU on my machine has to wait for ~400 cycles for data, an eternity.

If you want a run-down of the 1.3 changes and the design decisions behidn those changes, check out the LonestarElixir Phoenix 1.3 keynote: https://www.youtube.com/watch?v=tMO28ar0lW8

To use the new phx.new project generator, you can install the archive with the following command:

$ mix archive.install https://github.com/phoenixframework/archives/raw/master/phx_new.ez

Bump your phoenix dep

Phoenix v1.3.0 is a backwards compatible release with v1.2.x. To upgrade your existing 1.2.x project, simply bump your phoenix dependency in mix.exs:

Rich Already Answered That!

A list of commonly asked questions, design decisions, reasons why Clojure is the way it is as they were answered directly by Rich (even when from many years ago, those answers are pretty much valid today!). Feel free to point friends and colleagues here next time they ask (again). Answers are pasted verbatim (I've made small adjustments for readibility, but never changed a sentence) from mailing lists, articles, chats.

How to use:

The link in the table of content jumps at the copy of the answer on this page.
The link on the answer itself points back at the original post.

	#include <assert.h>
	#include <stdarg.h>
	#include <stdbool.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>

	enum type {
	NIL,

	# !/bin/bash

	# Copyright (c) 2011 Float Mobile Learning
	# http://www.floatlearning.com/
	#
	# Permission is hereby granted, free of charge, to any person obtaining
	# a copy of this software and associated documentation files (the "Software"),
	# to deal in the Software without restriction, including without limitation
	# the rights to use, copy, modify, merge, publish, distribute, sublicense,
	# and/or sell copies of the Software, and to permit persons to whom the

	(ns async-test.timeout.core
	(:require [cljs.core.async :refer [chan close!]])
	(:require-macros
	[cljs.core.async.macros :as m :refer [go]]))

	(defn timeout [ms]
	(let [c (chan)]
	(js/setTimeout (fn [] (close! c)) ms)
	c))

	module FParsecTrace

	open FParsec
	open FParsec.Primitives
	open FParsec.CharParsers

	open System.Text

	type DebugInfo = { Message: string; Indent: int }
	type UserState = { mutable Debug: DebugInfo }

	//********************************************************//

	// HOW TO:
	// Create a file called devenv.pkgundef in the same directory as devenv.exe.
	// It's usually located at C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE
	// Then call "devenv.exe /updateconfiguration" from an elevated command prompt.

	// REMARKS:
	// Each GUID below represent a package that Visual Studio is loading. This is the
	// list of package that I personally don't ever use. You can modify the list of