Papers I like Pt. 1 Papers I like Pt. 2
Let's start meta:
#Understanding closures, callbacks and promises
For a code newbie like myself, callbacks, closures and promises are scary JavaScript concepts.
10 months into my full-time dev career, and I would struggle to explain these words to a peer.
So I decided it was time to face my fears, and try to get my head around each concept.
Here are the notes from my initial reading. I'll continue to refine them as my understanding improves.
The Liang-Barsky algorithm is a cheap way to find the intersection points between a line segment and an axis-aligned rectangle. It's a simple algorithm, but the resources I was pointed to didn't have particularly good explanations, so I tried to write a better one.
Consider a rectangle defined by x_min ≤ x ≤ x_max and y_min ≤ y ≤ y_max, and a line segment from (x_0, y_0) to (x_0 + Δ_x, y_0 + Δ_y). We'll be assuming at least one of Δ_x and Δ_y is nonzero.
(I'm working with Flash, so I'll be using the convention that y increases as you go down.)
We want to distinguish between the following cases:
| 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 |
