A few notes on branch prediction and microbenchmarking Clojure comparisons
There are times when you need to do a large number of comparison operations, for example when implementing a sort or a tree structure. Clojure has provided a helpful core function to compare items that implement the Comparable interface:
(compare 2 5)
;; => -1
| ;;;; mem-usage.lisp | |
| ;;; MEM-USAGE returns memory used by Lisp image in a plist. | |
| ;;; MEM-USED prints memory allocated while running the given forms. | |
| ;;; Works on SBCL, CMUCL, CCL and CLISP. | |
| ;;; Relies on internal APIs (the ones that ROOM uses). Can break at any time. | |
| (defpackage #:mem-usage | |
| (:use #:cl) | |
| (:export #:mem-usage #:mem-used)) |
Simply put, destructuring in Clojure is a way extract values from a datastructure and bind them to symbols, without having to explicitly traverse the datstructure. It allows for elegant and concise Clojure code.
Simply put, destructuring in Clojure is a way extract values from a datastructure and bind them to symbols, without having to explicitly traverse the datstructure. It allows for elegant and concise Clojure code.
| ;;; -*- Mode:Common-Lisp; Package:System; Base:10 -*- | |
| ;; RESTRICTED RIGHTS LEGEND | |
| ;; | |
| ;; Use, duplication, or disclosure by the Government is subject to | |
| ;; restrictions as set forth in subdivision (c)(1)(ii) of the Rights in | |
| ;; Technical Data and Computer Software clause at 52.227-7013. | |
| ;; | |
| ;; TEXAS INSTRUMENTS INCORPORATED. | |
| ;; P.O. BOX 2909 |
| public class SystemClock { | |
| public static long lastTime = 0; | |
| /** | |
| * Returns a strictly increasing time in number of 100 ns that passed since Unix Epoch. | |
| */ | |
| public static synchronized long getTime() { | |
| long time = System.currentTimeMillis() * 10L*1000L; | |
| if (time <= lastTime) { |
| (ns clock) | |
| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; | |
| ;; Lock-Free Thread-safe Monotonic Clock | |
| ;; Dan Lentz <http://github.com/danlentz> | |
| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; | |
| ;; We use epoch stamp (milliseconds) and zero-pad the low order bits | |
| ;; of millisecond stamp and provide atomic incremental | |
| ;; uuids-this- second subcounter on the low order bits, which | |
| ;; guarantee that two timestamps never collide regardless of clock |
| ;; Datomic example code | |
| (use '[datomic.api :only (db q) :as d]) | |
| ;; ?answer binds a scalar | |
| (q '[:find ?answer :in ?answer] | |
| 42) | |
| ;; of course you can bind more than one of anything | |
| (q '[:find ?last ?first :in ?last ?first] | |
| "Doe" "John") |
| The regex patterns in this gist are intended only to match web URLs -- http, | |
| https, and naked domains like "example.com". For a pattern that attempts to | |
| match all URLs, regardless of protocol, see: https://gist.github.com/gruber/249502 | |
| # Single-line version: | |
| (?i)\b((?:https?:(?:/{1,3}|[a-z0-9%])|[a-z0-9.\-]+[.](?:com|net|org|edu|gov|mil|aero|asia|biz|cat|coop|info|int|jobs|mobi|museum|name|post|pro|tel|travel|xxx|ac|ad|ae|af|ag|ai|al|am|an|ao|aq|ar|as|at|au|aw|ax|az|ba|bb|bd|be|bf|bg|bh|bi|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|ch|ci|ck|cl|cm|cn|co|cr|cs|cu|cv|cx|cy|cz|dd|de|dj|dk|dm|do|dz|ec|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|gd|ge|gf|gg|gh|gi|gl|gm|gn|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|hr|ht|hu|id|ie|il|im|in|io|iq|ir|is|it|je|jm|jo|jp|ke|kg|kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|ma|mc|md|me|mg|mh|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|mv|mw|mx|my|mz|na|nc|ne|nf|ng|ni|nl|no|np|nr|nu|nz|om|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|ps|pt|pw|py|qa|re|ro|rs|ru|rw|sa|sb|sc|sd|se|sg|sh|si|s |