## (Random Musings) On Floats and Encodings

31/01/2012

The float and double floating-point data types have been present for a long time in the C (and C++) standard. While neither the C nor C++ standards do not enforce it, virtually all implementations comply to the IEEE 754—or try very hard to. In fact, I do not know as of today of an implementation that uses something very different. But the IEEE 754-type floats are aging. GPU started to add extensions such as short floats for evident reasons. Should we start considering adding new types on both ends of the spectrum?

The next step up, the quadruple precision float, is already part of the standard, but, as far as I know, not implemented anywhere. Intel x86 does have something in between for its internal float format on 80 bits, the so-called extended precision, but it’s not really standard as it is not sanctioned by the IEEE standards, and, generally speaking, and surprisingly enough, not really supported well by the instruction set. It’s sometimes supported by the long double C type. But, anyway, what’s in a floating point number?

## Medians (Part III)

24/01/2012

So in the two previous parts of this series, we have looked at the selection algorithm and at sorting networks for determining efficiently the (sample) median of a series of values.

In this last installment of the series, I consider an efficient (but approximate) algorithm based on heaps to compute the median.

## Wallpaper: Frontières imaginées

21/01/2012

(Frontières imaginées, 1920×1200)

You can find more wallpapers here

## Wallpaper: Sibérie minimaliste

21/01/2012

(Sibérie Minimaliste, 1920×1200)

You can find more wallpapers here

## Lossless Coding of CD Audio

17/01/2012

Once upon a time, I discussed how to pick bit-rate for MP3, while considering re-ripping all my CDs. But if I’m to re-rip everything, I might as well do it one last time and use lossless compression.

In this post, we’ll discuss the simple script I cooked up to do just that, and a bit on how Flac works, and how it compares to MP3.

## Suggested Reading: National Audubon Society Guide To Photographing National Parks

15/01/2012

Tim Fitzharris — National Audubon Society Guide To Photographing National Parks (Digital Edition) — Firefly Books 2009, 192 pp. ISBN 978-1-55407-455-6

Contrary to what the title may indicate, this book has little to do with actual digital photography techniques for landscapes or natural wonders; it is rather a tourist guide of everything you should see in the major american national parks. After expediting the basics of landscape photography, the guide leads you into a detailed journey into the United States major national parks, giving you all the good hints as to how to reach this-or-that natural wonder, what time of year, or even the time of day will lend itself the best for photography.

While this seems moderately interesting for a foreigner (especially if one doesn’t really want to visit all the state parks), the book is entirely redeemed by Fitzharris’ absolutely superb photography. A must get, especially if you’re interested in landscape photography.

## Suggested Reading: The Practical Pyromaniac

15/01/2012

William Gurstelle — The Practical Pyromaniac: Build Fire Tornadoes, One-Candlepower Engines, Great Balls of Fire, and More Incendiary Devices — Chicago Review Press, 2011, 212 pp. ISBN 978-1-56976-710-8

This book is quite the step up from Mini Weapons Of Mass Destruction 2: not only the projects presented are a lot more interesting—flame-thrower and all—they are presented in their historical and scientific contexts, explaining the active principles of each device/contraption. While Mini Weapons was something of a kid’s book, The Practical Pyromaniac certainly isn’t. I must say it will appeal quite a lot to every one with a little envie de destruction.

## Medians (Part II)

10/01/2012

In the previous post of this series, we left off where we were asking ourselves if there was a better way than the selection algorithm of finding the median.

Computing the median of three numbers is a simple as sorting the three numbers (an operation that can be done in constant time, after all, if comparing and swapping are constant time) and picking the middle. However, if the objects compared are “heavy”, comparing and (especially) moving them around may be expensive.

## Building a Balanced Tree From a List in Linear Time

03/01/2012

The usual way of forming a search tree from a list is to scan the list and insert each of its element, one by one, into the tree, leading to a(n expected) run-time of $O(n \lg n)$.

However, if the list is sorted (in ascending order, say) and the tree is not one of the self-balancing varieties, insertion is $O(n^2)$, because the “tree” created by the successive insertions of sorted key is in fact a degenerate tree, a list. So, what if the list is already sorted and don’t really want to have a self-balancing tree? Well, it turns out that you can build a(n almost perfectly) balanced tree in $O(n)$.