Big List of 20 Common Bottlenecks

“In Zen And The Art Of Scaling – A Koan And Epigram Approach, Russell Sullivan offered an interesting conjecture: there are 20 classic bottlenecks. This sounds suspiciously like the idea that there only 20 basic story plots. And depending on how you chunkify things, it may be true, but in practice we all know bottlenecks come in infinite flavors, all tasting of sour and ash.

One day Aurelien Broszniowski from Terracotta emailed me his list of bottlenecks, we cc’ed Russell in on the conversation, he gave me his list, I have a list, and here’s the resulting stone soup.

Russell said this is his “I wish I knew when I was younger” list and I think that’s an enriching way to look at it. The more experience you have, the more different types of projects you tackle, the more lessons you’ll be able add to a list like this. So when you read this list, and when you make your own, you are stepping through years of accumulated experience and more than a little frustration, but in each there is a story worth grokking…”

http://highscalability.com/blog/2012/5/16/big-list-of-20-common-bottlenecks.html

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Which hashing algorithm is best for uniqueness and speed?

http://programmers.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed/145633#145633

Introducing CityHash

“We’re pleased to announce the new CityHash family of hash functions for strings. We’re releasing two functions today: CityHash64 and CityHash128. They hash strings to 64- and 128-bit hash codes, respectively. These functions aren’t suitable for cryptography, but our experience so far shows that they’re great for, say, hash tables.

We tried to optimize for CPUs that are common in Google’s datacenters, but it turns out that most PCs and laptops have the relevant features as well. The important ones are 64-bit registers, instruction-level parallelism, and fast unaligned memory accesses.

We were greatly inspired by previous work on hashing, especially Austin Appleby’s MurmurHash. The key advantage of our approach is that most steps contain at least two independent mathematical operations. Modern CPUs tend to perform best with this type of code.

The disadvantage of our approach is that the code is more complicated than most popular alternatives. We decided to optimize for speed rather than simplicity and even included special cases for short inputs.

Overall, we believe that CityHash64 and CityHash128 are exciting new ways to solve a classic problem. Under real-life conditions we expect CityHash64 to outperform previous work by at least 30% in speed, and perhaps as much as a factor of two. Also, as far as we know, these functions’ statistical properties are sound. Please don’t hesitate to try this fast new code!…”

http://google-opensource.blogspot.in/2011/04/introducing-cityhash.html

Revisiting why incompetents think they’re awesome

“In 1999 a pair of researchers published a paper called “Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments (PDF).” David Dunning and Justin Kruger (both at Cornell University’s Department of Psychology at the time) conducted a series of four studies showing that, in certain cases, people who are very bad at something think they are actually pretty good. They showed that to assess your own expertise at something, you need to have a certain amount of expertise already…”

http://arstechnica.com/science/2012/05/revisiting-why-incompetents-think-theyre-awesome/