Goals: Add links that are reasonable and good explanations of how stuff works. No hype and no vendor content if possible. Practical first-hand accounts of models in prod eagerly sought.
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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 |
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/** | |
* Fancy ID generator that creates 20-character string identifiers with the following properties: | |
* | |
* 1. They're based on timestamp so that they sort *after* any existing ids. | |
* 2. They contain 72-bits of random data after the timestamp so that IDs won't collide with other clients' IDs. | |
* 3. They sort *lexicographically* (so the timestamp is converted to characters that will sort properly). | |
* 4. They're monotonically increasing. Even if you generate more than one in the same timestamp, the | |
* latter ones will sort after the former ones. We do this by using the previous random bits | |
* but "incrementing" them by 1 (only in the case of a timestamp collision). | |
*/ |
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;; based on core.logic 0.8-alpha2 or core.logic master branch | |
(ns sudoku | |
(:refer-clojure :exclude [==]) | |
(:use clojure.core.logic)) | |
(defn get-square [rows x y] | |
(for [x (range x (+ x 3)) | |
y (range y (+ y 3))] | |
(get-in rows [x y]))) |
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Philosophical: | |
* writing lines of code is one of the least valuable things I can do | |
* cultivate your impatience | |
* reject the status quo, unless we can re-derive it from first-principles | |
* engineers imprint on the first languages (techniuqes, frameworks or technology) that we find success with (unconsciously seen as caregivers, which we defend w/o always knowing why) | |
* we tend to overvalue the familiar/known; we tend to undervalue the unfamiliar/unknown, this interferes with our receptiveness to new ideas and personal growth | |
* we're 90% composed of bad habits; many of our best habits become bad as time passes; this allows us to filter for the fundamental; the great | |
* make doing the right thing easier than any other thing, or we will fail to achieve greatness, or break bad habits | |
* be conscious, be intentional | |
* "is this the highest we can aim?" (I prefer this over "is this the best we can do", the former is aspirational, the latter is judgemental) |
The reason why you might get certificate errors in Ruby 2.0 when talking HTTPS is because there isn't a default certificate bundle that OpenSSL (which was used when building Ruby) trusts.
Update: this problem is solved in edge versions of rbenv and RVM.
$ ruby -rnet/https -e "Net::HTTP.get URI('https://github.com')"
net/http.rb:917:in `connect': SSL_connect returned=1 errno=0 state=SSLv3
read server certificate B: certificate verify failed (OpenSSL::SSL::SSLError)
You can work around the issue by installing a certificate bundle that you trust. I trust Mozilla and curl.
A primer/refresher on the category theory concepts that most commonly crop up in conversations about Scala or FP. (Because it's embarassing when I forget this stuff!)
I'll be assuming Scalaz imports in code samples, and some of the code may be pseudo-Scala.
A functor is something that supports map
.
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package main | |
import ( | |
"fmt" | |
) | |
type Node struct { | |
Value int | |
} |
Prerequisites:
- One or more clients running a UNIX-like OS. Examples are given for Ubuntu 12.04 LTS, although all software components are available for other platforms as well (e.g. OS X). YMMV
- A cheap Ubuntu 12.04 VPS with storage. I recommend Backupsy, they offer 250GB storage for $5/month. Ask Google for coupon codes.
Software components used:
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