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New
The latest blog posts to take off on Hacker News. 163 posts.
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Sunset Geometry (2016)
Robert Vanderbei has written a beautiful series of articles and talks about a method for finding the radius of the earth based on a single photograph of a sunset over a large, calm lake.
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Solving NP-hard puzzles with the oldest trick in the book
KOITOTO hadir dengan mengutamakan kemudahan akses serta dukungan bagi pengguna yang membutuhkan informasi seputar layanan dan navigasi situs.
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Conterintuitive facts in mathematics, CS, and physics
It is possible to compute over encrypted data without access to the secret key: https://en.wikipedia.org/wiki/Homomorphic_encryption
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Maybe the spaghetti code conjecture is false
The Spaghetti Code Conjecture says that Busy Beaver programs ought to be, in some sense, as complicated as possible. Scott Aaronson puts it this way:
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How percentile approximation works and why it's more useful than averages
What percentile approximations are, how percentiles work in PostgreSQL, and calculating them efficiently on time-series data.
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Why can’t I go faster than the speed of light?
I should state from the very beginning that the title of this post is a bit of a tease. I don’t know why nothing can go faster than the speed of light. No one does. It is a fundamental pos…
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NP Complete 3rd Grade Math Problems (2018)
Leo’s third grade class got to try a Noyce Foundation math worksheet [1] the other day. They didn’t fare so well, but I gotta tell you, some of the problems are REALLY hard! In fact, on…
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High Performance Correctly Rounded Math Libraries for 32-Bit Floating Point
Everyone uses math libraries. Surprisingly, mainstream math libraries do not produce correct results for several thousands of inputs. Developers are seldom aware of them, which affects reproducibil…
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The Mathematics of 2048: Optimal Play with Markov Decision Processes (2018)
Finding provably optimal strategies for 2048 using Markov Decision Processes
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Rolling hash; Rabin-Karp string search
This is yet another string search algorithm. (Previously my readers have read about Knuth-Morris-Pratt .)
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Speeding up atan2f
`atan2f` is an important but slow trigonometric function. In this article we'll explain how to approximate it, and implement a version 50x faster than `glibc` on batches of inputs.
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The Inconsistency of Arithmetic (2011)
Note: These pages make extensive use of the latest XHTML and CSS Standards . They ought to look great in any standards-compliant modern browser. Unfortunately, they will probably look horrible in older browsers, like Netscape 4.x and IE 4.x. Moreover, many posts use MathML, which is, currently only supported in…
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Difficult math is about recognizing patterns
Jeff Bezos tells a great story about the smartest guy he knew at Princeton. He and a classmate were working on a really tough partial differential equation and getting nowhere. They spent 3 hours on the problem and gave up.
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Bloom Filters: More than a space-efficient hashmap
A bloom filter is one of those data structures you are probably already aware of, or have at least heard about. For those looking for a simple recap, they are a probabilistic data structure which can …
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Computational algebraic geometry for high school students
Can high school students really learn algebraic geometry? And what could it teach us about mathematics education?
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The Poincaré Conjecture, Explained
Poincaré began working on what is now considered to be the foundation of topology and algebraic topology in the 1890s with the work Analysis Situs (1895) and five later supplements (1899; 1900, 1902a, 1902b, 1904).
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What time-weighted averages are and why you should care
Learn how time-weighted averages are calculated and why they’re so powerful for data analysis. Read the full article on the Tiger Data blog.
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Using Benford’s Law to Detect Bitcoin Manipulation
Economist Gary Smith sends along this post with the above title and the subtitle, “Market prices are not invariably equal to intrinsic values.” Here’s Smith: