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Filling large arrays with zeroes quickly in C++
From Daniel Lemire's Blog

Filling large arrays with zeroes quickly in C++

Travis Downs reports that some C++ compilers have trouble filling up arrays with values at high speed. Typically, to fill an array with some value, C++ programmers...

Allocating large blocks of memory: bare-metal C++ speeds
From Daniel Lemire's Blog

Allocating large blocks of memory: bare-metal C++ speeds

In a previous post, I benchmarked the allocation of large blocks of memory using idiomatic C++. I got a depressing result: the speed could be lower than 2 GB/s....

How fast can you allocate a large block of memory in C++?
From Daniel Lemire's Blog

How fast can you allocate a large block of memory in C++?

In C++, the most basic memory allocation code is just a call to the new operator: char *buf = new char[s]; According to a textbook interpretation, we just allocated...

Science and Technology links (January 11th 2020)
From Daniel Lemire's Blog

Science and Technology links (January 11th 2020)

The extra wealth that ones acquires by attending college is now estimated to be indistinguishable from zero. The authors control for the parent’s education andContinue...

How I teach database design
From Daniel Lemire's Blog

How I teach database design

Most software runs on top of databases. These databases are organized logically, with a schema, that is a formal description. You have entities (your user), attributes...

My Science and Technology review for  2019
From Daniel Lemire's Blog

My Science and Technology review for 2019

I like to end every year with my selection of the most significant science and technology events. In 2019, you could buy a computer from Apple with 1.5 terabytes...

Science and Technology links (December 21st 2019)
From Daniel Lemire's Blog

Science and Technology links (December 21st 2019)

The number of research papers with more than 1000 authors is increasingly quickly and reaching many fields. Researchers at Facebook use neural networks to solve...

Xor Filters: Faster and Smaller Than Bloom Filters
From Daniel Lemire's Blog

Xor Filters: Faster and Smaller Than Bloom Filters

In software, you frequently need to check whether some objects is in a set. For example, you might have a list of forbidden Web addresses. As someone enters a new...

A look back to my 2010 predictions for 2020
From Daniel Lemire's Blog

A look back to my 2010 predictions for 2020

Back in 2010, I wrote a post Who is going to need a database engine in 2020? Let me revisit some of my 2010 statements. Apple will sell desktops with 1 TB of RAM...

Science and Technology links (December 14th 2019)
From Daniel Lemire's Blog

Science and Technology links (December 14th 2019)

The computation capacity needed by artificial intelligence doubles every 3.4 months. In parallel, we are making fast progress in hardware and software: what took...

Are 64-bit random identifiers free from collision?
From Daniel Lemire's Blog

Are 64-bit random identifiers free from collision?

It is common in software system to map objects to unique identifiers. For example, you might map all web pages on the Internet to a unique identifier. Often, these...

Amazon’s new ARM servers: Graviton 2
From Daniel Lemire's Blog

Amazon’s new ARM servers: Graviton 2

Most servers on the Internet run on x64 processors, mostly made by Intel. Meanwhile, most smartphones run ARM processors. From a business perspective, these are...

Science and Technology links (December 7th 2019)
From Daniel Lemire's Blog

Science and Technology links (December 7th 2019)

Incredibly, there is a new simpler way to solve the quadratic formula. I used to rely on the completion of the square, but this is better! There is a video report...

AMD Zen 2 and branch mispredictions
From Daniel Lemire's Blog

AMD Zen 2 and branch mispredictions

Intel makes some of the very best processors many can buy. For a long time, its main rival (AMD) failed to compete. However, its latest generation of processors...

Instructions per cycle: AMD Zen 2 versus Intel
From Daniel Lemire's Blog

Instructions per cycle: AMD Zen 2 versus Intel

The performance of a processor is determined by several factors. For example, processors with a higher frequency tend to do more work per unit of time. PhysicsContinue...

Better computational complexity does not imply better speed
From Daniel Lemire's Blog

Better computational complexity does not imply better speed

A recent magazine article presents a theoretical result: Harvey and van der Hoeven have shown that you can multiply two n-bit integers using O(n log n) complexity...

Memory parallelism: AMD Rome versus Intel
From Daniel Lemire's Blog

Memory parallelism: AMD Rome versus Intel

When thinking about “parallelism”, most programmers think about having multiple processors. However, even a single core in a modern processor has plenty of parallelism...

Cloud computing: a story of incentives
From Daniel Lemire's Blog

Cloud computing: a story of incentives

Many businesses today run “in the cloud”. What this often means is that they have abstracted out the hardware entirely. Large corporations like Amazon, Google,Continue...

Science and Technology links (November 16th 2019)
From Daniel Lemire's Blog

Science and Technology links (November 16th 2019)

We have new technology to do genetic engineering on human beings (CRISPR). In a small clinical trial, the researchers tested it on live human subjects and found...

Unrolling your loops can improve branch prediction
From Daniel Lemire's Blog

Unrolling your loops can improve branch prediction

Modern processors predict branches (e.g., if-then clauses), often many cycles a ahead of time. When predictions are incorrect, the processor has to start again,...
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