AlexAti’s gists

flyingmachine / gist:4004807

Created November 2, 2012 22:41

clojure korma heroku db connection

	(defdb db
	(if (System/getenv "DATABASE_URL")
	(let [db-uri (java.net.URI. (System/getenv "DATABASE_URL"))
	user-and-password (clojure.string/split (.getUserInfo db-uri) #":")]
	{:classname "org.postgresql.Driver"
	:subprotocol "postgresql"
	:user (get user-and-password 0)
	:password (get user-and-password 1) ; may be nil
	:subname (if (= -1 (.getPort db-uri))
	(format "//%s%s" (.getHost db-uri) (.getPath db-uri))

jboner / latency.txt

Last active May 17, 2024 01:05

Latency Numbers Every Programmer Should Know

	Latency Comparison Numbers (~2012)
	----------------------------------
	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 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

pingles / bytes_to_int.clj

Created September 22, 2011 17:01

Clojure code to convert a byte array to an integer

	(defn bytes-to-int
	([bytes]
	(bytes-to-int bytes 0))
	([bytes offset]
	(reduce + 0
	(map (fn [i]
	(let [shift (* (- 4 1 i)
	8)]
	(bit-shift-left (bit-and (nth bytes (+ i offset))
	0x000000FF)

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