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
Almost picking N distinct numbers at random
In Picking N distinct numbers at random: how to do it fast?, I describe how to quickly pick N distinct values are random from a range of values. It comes down to...
From Daniel Lemire's Blog
Science and Technology links (May 4th 2019)
It is often believed that colleges help class mobility… if you were born poor, college can help your rise up. So is there more class mobility when more people go...
From Daniel Lemire's Blog
Really fast bitset decoding for “average” densities
Suppose I give you a word and you need to determine the location of the 1-bits. For example, given the word 0b100011001, you would like to get 0,3,4,8. You could...
From Daniel Lemire's Blog
Science and Technology links (April 27th 2019)
Women who use oral contraceptives have a harder time recognizing emotions of others. Worldwide, livestock has ten times the mass of wild animals and nearly twice...
From Daniel Lemire's Blog
Speeding up a random-access function?
A common problem in software performance is that you are essentially limited by memory access. Let us consider such a function where you write at random locations...
From Daniel Lemire's Blog
The shopper’s dilemma: wait for new technology or buy now?
Technology is accelerating. It took less than a decade for smartphone to go from 1% of the population to almost everyone. Television took longer. The phone even...
From Daniel Lemire's Blog
Science and Technology links (April 20th 2019)
Early-career setback cause a performance improvement among those who persevere. This is related to the observation that immigrants are four times more likely to...
From Daniel Lemire's Blog
Parsing short hexadecimal strings efficiently
It is common to represent binary data or numbers using the hexadecimal notation. Effectively, we use a base-16 representation where the first 10 digits are 0, 1...
From Daniel Lemire's Blog
Science and Technology links (April 13th 2019)
There is little evidence that digital screens are harmful to teenager’s mental health. If there is an effect, it is small. Cotton bags must be reused thousandsContinue...
From Daniel Lemire's Blog
Why are unrolled loops faster?
A common optimization in software is to “unroll loops”. It is best explained with an example. Suppose that you want to compute the scalar product between two arrays...
From Daniel Lemire's Blog
Science and Technology links (April 6th 2019)
In a randomized trial where people reduced their caloric intake by 15% for two years, it was found that reducing calories slowed aging. This is well documentedContinue...
From Daniel Lemire's Blog
Science and Technology links (March 30th 2019)
As we age, we accumulate old and useless (senescent) cells. These cells should die, but they do not. Palmer et al. removed senescent cells in obese mice. They found...
From Daniel Lemire's Blog
Java is not a safe language
The prime directive in programming is to write correct code. Some programming languages make it easy to achieve this objective. We can qualify these languages as...
From Daniel Lemire's Blog
Hasty comparison: Skylark (ARM) versus Skylake (Intel)
In a previous post, I ran a benchmark on an ARM server and again on an Intel-based server. My purpose was to indicate that if one function is faster, even much...
From Daniel Lemire's Blog
Technological aging
We are all familiar with biological aging. Roughly speaking, it is the loss of fitness that most animals undergo with time. At the present time, there is simply...
From Daniel Lemire's Blog
Science and Technology links (March 23rd 2019)
Half of American households subscribe to “Amazon Prime”, a “club membership” for Amazon customers with monthly fees. And about half of these subscribes buy something...
From Daniel Lemire's Blog
ARM and Intel have different performance characteristics: a case study in random number generation
In my previous post, I reviewed a new fast random number generator called wyhash. I commented that I expected it to do well on x64 processors (Intel and AMD), but...
From Daniel Lemire's Blog
The fastest conventional random number generator that can pass Big Crush?
In software, we sometimes want to generate (pseudo-)random numbers. The general strategy is to have a state (e.g., a 64-bit integer) and modify it each time weContinue...
From Daniel Lemire's Blog
Don’t read your data from a straw
It is common for binary data to be serialized to bytes. Data structures like indexes can be saved to disk or transmitted over the network in such a form. Many serialized...
From Daniel Lemire's Blog