Communications of the ACM
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How the “Frontier” Became the Slogan of Uncontrolled AI
Artificial intelligence (AI) has been billed as the next frontier of humanity: the newly available expanse whose exploration …
From Daniel Lemire's Blog
When accessing hash tables, how much time is spent computing the hash functions?
Suppose that you create a large set of objects that you store in a hash table. Let us take 10 millions objects. It is large enough that it probably will not fit...
From Daniel Lemire's Blog
When shuffling large arrays, how much time can be attributed to random number generation?
It is well known that contemporary computers don’t like to randomly access data in an unpredictible manner in memory. However, not all forms of random accessesContinue...
From Daniel Lemire's Blog
Science and Technology links (March 23rd, 2018)
Sending your kids to highly selective schools is maybe less useful than you think: “However, once we controlled for factors involved in pupil selection, (…) the...
From Daniel Lemire's Blog
Science and Technology links (March 16th, 2018)
From the beginning of the 20th century to 2010, the life expectancy at birth for females in the United States increased by more than 32 years. The 3 major causes...
From Daniel Lemire's Blog
Iterating over hash sets quickly in Java
There are many ways in software to represent a set. The most common approach is to use a hash table. We define a “hash function” that takes as an input our elements...
From Daniel Lemire's Blog
Science and Technology links (March 9th, 2018)
The Audi A8, which goes on sale this year, will be the first car to offer Level 3 autonomy, which means that as a driver, you are expected to be able to relinquish...
From Daniel Lemire's Blog
Iterating over set bits quickly (SIMD edition)
Suppose that you have a long sequence of bits 10101011100000… you want to visit all the bits set to 1. That is, given 10101011100000, you would like to get theContinue...
From Daniel Lemire's Blog
Science and Technology links (March 2nd, 2018)
Flashing lights might cure Alzheimer’s, according to Nature. There is no paradox: being obese is definitively bad for you. Class attendance predicts success inContinue...
From Daniel Lemire's Blog
Vectorized shifts: are immediates faster?
Our processors are all equipped with vector instructions also called SIMD (single instruction multiple data). One common instruction is the “shift”. Roughly speaking...
From Daniel Lemire's Blog
Science and Technology links (February 24th, 2018)
Samsung is manufacturing and will sell 30TB hard drives. That’s huge. It is enough to record everything you see and hear for three years. Of the cases of early-onset...
From Daniel Lemire's Blog
Iterating over set bits quickly
A common problem in my line of work is to iterate over the set bits (bits having value 1) in a large array. My standard approach involves a “counting trailing zeroes...
From Daniel Lemire's Blog
Science and Technology links (February 16th, 2018)
In all countries, in all years–without exception–girls did better than boys in academic performance (PISA) tests. Vinod Khosla said: There are, perhaps, a few hundred...
From Daniel Lemire's Blog
Science and Technology links (February 9th, 2018)
We shed 50 million skin cells every day. A mutant crayfish reproduces by cloning. To my knowledge, this might be the largest animal to reproduce by cloning. Before...
From Daniel Lemire's Blog
Don’t underestimate the nerds
I’m a little nerdy. According to my wife, I even look like a nerd. I am not very big. I have a long resume posted online, and I’ll proudly post my follower count...
From Daniel Lemire's Blog
Science and Technology links (February 2nd, 2018)
Most mammals, including human beings, age according to a Gompertz curve. It is a fancy way of saying that your risk of death goes up exponential with age. Naked...
From Daniel Lemire's Blog
Picking distinct numbers at random: benchmarking a brilliant algorithm (JavaScript edition)
Suppose you want to choose m distinct integers at random within some interval ([0,n)). How would you do it quickly? I have a blog post on this topic dating back...
From Daniel Lemire's Blog
Science and Technology links (January 26th, 2018)
We have reached “peak coal” meaning that coal usage is going to diminish in the coming years. McGill professor Ishiang Shih has been accused by the US government...
From Daniel Lemire's Blog
Initializing arrays quickly in Swift: be wary of Sadun’s initializers
Swift is Apple’s go-to programming language. It is the new default to build applications for iPhones. It also runs well on Linux. It is not as low-level as C or...
From Daniel Lemire's Blog
Microbenchmarking is hard: virtual machine edition
To better understand software performance, we often use small controlled experiments called microbenchmarks. In an earlier post, I remarked that it is hard to reason...
From Daniel Lemire's Blog