posener

Be Careful with Table Driven Tests and t.Parallel()

We Gophers, love table-driven-tests, it makes our unittesting structured, and makes it easy to add different test cases with ease.

Let’s create our table driven test, for convenience, I chose to use t.Log as the test function. Notice that we don't have any assertion in this test, it is not needed to for the demonstration.

func TestTLog(t *testing.T) {
	t.Parallel()

vasanthk

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

mfuerstenau

  ZigZag-Encoding
  ---------------
  
  Maps negative values to positive values while going back and
  forth (0 = 0, -1 = 1, 1 = 2, -2 = 3, 2 = 4, -3 = 5, 3 = 6 ...)

  (i >> bitlength-1) ^ (i << 1)

  with "i" being the number to be encoded, "^" being
  XOR-operation and ">>" would be arithemtic shifting-operation

cdipaolo

// haversin(θ) function
func hsin(theta float64) float64 {
	return math.Pow(math.Sin(theta/2), 2)
}

// Distance function returns the distance (in meters) between two points of
//     a given longitude and latitude relatively accurately (using a spherical
//     approximation of the Earth) through the Haversin Distance Formula for
//     great arc distance on a sphere with accuracy for small distances
//

smhanov

// By Steve Hanov (2014)
// Released to public domain
//
// Minimum element is always on top.
// You can pass in an optional lessThan(a, b) function to the constructor.
// You may use .length to retrieve the length. Try not to set it though.

function Heap()
{
    if (arguments.length) {

smhanov

#!/usr/bin/python3
# By Steve Hanov, 2011. Released to the public domain.
# Please see http://stevehanov.ca/blog/index.php?id=115 for the accompanying article.
#
# Based on Daciuk, Jan, et al. "Incremental construction of minimal acyclic finite-state automata." 
# Computational linguistics 26.1 (2000): 3-16.
#
# Updated 2014 to use DAWG as a mapping; see 
# Kowaltowski, T.; CL. Lucchesi (1993), "Applications of finite automata representing large vocabularies", 
# Software-Practice and Experience 1993

jboner

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

nzjrs

all: test libtest.so testmodule

libtest.so: libtest.c
	$(CC) -Wall -g -fPIC -shared -o $@ $? -lc

test: test_main.c libtest.o
	$(CC) -o $@ $?

testmodule: testmodule.c
	python setup.py build