Product Description

Veteran programmer Hank Warren shares the tricks he has collected from his considerable experience in the worlds of application and system programming. For anyone who wants to create efficient code. Self-directed study.

---

Product Details

• Amazon Sales Rank: #35252 in Books
• Published on: 2002-07-27
• Original language: English
• Number of items: 1
• Binding: Hardcover
• 306 pages

From the Back Cover

"This is the first book that promises to tell the deep, dark secrets of computer arithmetic, and it delivers in spades. It contains every trick I knew plus many, many more. A godsend for library developers, compiler writers, and lovers of elegant hacks, it deserves a spot on your shelf right next to Knuth."

--Josh Bloch

"When I first saw the title, I figured that the book must be either a cookbook for breaking into computers (unlikely) or some sort of compendium of little programming tricks. It's the latter, but it's thorough, almost encyclopedic, in its coverage."

--Guy Steele

These are the timesaving techniques relished by computer hackers--those devoted and persistent code developers who seek elegant and efficient ways to build better software. The truth is that much of the computer programmer's job involves a healthy mix of arithmetic and logic. In Hacker's Delight, veteran programmer Hank Warren shares the tricks he has collected from his considerable experience in the worlds of application and system programming. Most of these techniques are eminently practical, but a few are included just because they are interesting and unexpected. The resulting work is an irresistible collection that will help even the most seasoned programmers better their craft.

Topics covered include:

• A broad collection of useful programming tricks
• Small algorithms for common tasks
• Power-of-2 boundaries and bounds checking
• Rearranging bits and bytes
• Integer division and division by constants
• Some elementary functions on integers
• Gray code
• Hilbert's space-filling curve
• And even formulas for prime numbers!

This book is for anyone who wants to create efficient code. Hacker's Delight will help you learn to program at a higher level--well beyond what is generally taught in schools and training courses--and will advance you substantially further than is possible through ordinary self-study alone.

0201914654B06272002

About the Author

Henry S. Warren, Jr., has had a forty-year career with IBM, spanning from the IBM 704 to the PowerPC. He has worked on various military command and control systems and on the SETL project under Jack Schwartz at New York University. Since 1973 he has been with IBM's Research Division, focusing on compilers and computer architectures. Hank currently works on the Blue Gene petaflop computer project. He received his Ph.D. in computer science from the Courant Institute at New York University.

0201914654AB06272002

Excerpt. © Reprinted by permission. All rights reserved.

Caveat Emptor: The cost of software maintenance
increases with the square of the programmer's creativity.First Law of Programmer Creativity, Robert D. Bliss, 1992

This is a collection of small programming tricks that I have come across over many years. Most of them will work only on computers that represent integers in two's-complement form. Although a 32-bit machine is assumed when the register length is relevant, most of the tricks are easily adapted to machines with other register sizes.

This book does not deal with large tricks such as sophisticated sorting and compiler optimization techniques. Rather, it deals with small tricks that usually involve individual computer words or instructions, such as counting the number of 1-bits in a word. Such tricks often use a mixture of arithmetic and logical instructions.

It is assumed throughout that integer overflow interrupts have been masked off, so they cannot occur. C, Fortran, and even Java programs run in this environment, but Pascal and ADA users beware!

The presentation is informal. Proofs are given only when the algorithm is not obvious, and sometimes not even then. The methods use computer arithmetic, "floor" functions, mixtures of arithmetic and logical operations, and so on. Proofs in this domain are often difficult and awkward to express.

To reduce typographical errors and oversights, many of the algorithms have been executed. This is why they are given in a real programming language, even though, like every computer language, it has some ugly features. C is used for the high-level language because it is widely known, it allows the straightforward mixture of integer and bit-string operations, and C compilers that produce high-quality object code are available.

Occasionally, machine language is used. It employs a three-address format, mainly for ease of readability. The assembly language used is that of a fictitious machine that is representative of today's RISC computers.

Branch-free code is favored. This is because on many computers, branches slow down instruction fetching and inhibit executing instructions in parallel. Another problem with branches is that they may inhibit compiler optimizations such as instruction scheduling, commoning, and register allocation. That is, the compiler may be more effective at these optimizations with a program that consists of a few large basic blocks rather than many small ones.

The code sequences also tend to favor small immediate values, comparisons to zero (rather than to some other number), and instruction-level parallelism. Although much of the code would become more concise by using table lookups (from memory), this is not often mentioned. This is because loads are becoming more expensive relative to arithmetic instructions, and the table lookup methods are often not very interesting (although they are often practical). But there are exceptional cases.

Finally, I should mention that the term "hacker" in the title is meant in the original sense of an aficionado of computers--someone who enjoys making computers do new things, or do old things in a new and clever way. The hacker is usually quite good at his craft, but may very well not be a professional computer programmer or designer. The hacker's work may be useful or may be just a game. As an example of the latter, more than one determined hacker has written a program which, when executed, writes out an exact copy of itself1. This is the sense in which we use the term "hacker." If you're looking for tips on how to break into someone else's computer, you won't find them here.H. S. Warren, Jr.
Yorktown, New York
February 2002

1. The shortest such program written in C, known to the present author, is by Vlad Taeerov and Rashit Fakhreyev and is 64 characters in length: main(a){printf(a,34,a="main(a){printf(a,34,a=%c%s%c,34);}",34);}

0201914654P08282002

---

Customer Reviews

Magic
First of all, the book itself is incredible.

The title was poorly chosen, I think. The connotation of "hacker" in the public mind is somewhat different than the word's meaning forty years ago at MIT, and I found (and continue to find) this book shelved alongside ephemera about firewalls and internet security. Thinking it was about "1337 hacking", I picked it off the shelf for a quick sneer. Six hours later, the bookstore had to kick me out because they were closing.

Think of it as "The Art of Computer Programming, Volume 0: Bit Manipulation". Except without the annoying Knuth attitude.

"Hacker's Delight" is a timeless classic, a scholarly and exhaustive treatment of finite-word-length arithmetic and other bit-manipulation algorithms. The book is excellently written and the material lovingly presented. For some people (such as me), the mathematical beauty and cleverness of the solutions is reason enough to find the book fascinating. For other people (such as me), there are extensive practical applications.

However, the size of the latter group (or, perhaps, relative percentage) is dwindling with time. A programmer who thinks that the universe begins and ends with Oracle and PHP respectively is unlikely to need an 8-RISC-instruction algorithm for dividing integers by 7. The essence of programming is abstraction, and as computational resources become more abundant, the path of progress abstracts further and further away from the machine. For many modern programmers, there are no bits -- there are only "numbers" (double-precision floats, typically), and the hardware handles these floats just as gracefully as integers. In this world, one's complementing and shifting have no meaning.

Even for those working at a lower level, the caching and pipelining schemes of modern architectures can complicate some of the assumptions in this book. For example, branch performance is highly architecture-dependent, and the efficiency that can be gained through branch tuning can outweigh that of shaving off a few instructions. Warren is careful to provide and identify branch-free algorithms whenever possible, but it often is not. As another example, parallel instruction scheduling means that not only is a routine no longer the sum of its instructions' cycles, it's not even completely deterministic, at least from the programmer's perspective.

But I work in the embedded field, and my targets have ranged from 1 MHz 8-bit 6502s through 50 MHz 32-bit Coldfires to creatively-handicapped DSPs of various sorts. Not a FPU or branch predictor in sight. In such situations, the algorithms in "Hacker's Delight" can be lifesavers. Not to mention, so much fun! If you approach optimization as a puzzle, wherein the solution is its own reward, this book is indeed a compendium of delights.

Many descriptions of this book refer to it as a collection of programming "tricks". I dislike that word; it implies a casualness and triviality that does not befit a book of this rigor and scope. I prefer the subtitle of Johnson and Graham's text on high-speed digital design: "A Handbook of Black Magic".

If your magic dust is bits and cycles, this is your spellbook.

Reader's Delight
Early drafts of Dr Warren's book have circulated for several years samizdat style among a group of hardware, compiler and OS people at a large computer research lab. One copy in particular always sits about three feet from me. If the building were to catch on fire, you might very well hear shouts of "who's taking Hacker's Delight?"
How do you determine, using the smallest number of instructions, if a word contains at least one zero byte? How do you transpose a bit matrix? Divide by 5? Count the number of ones in a word? Permute bits? Maybe you're smart enough to already know. Or perhaps you know someone else who does. For the rest of us there's Hacker's Delight.
Some years back, in the course of building a large machine, we made a mistake that resulted in some very expensive rework. Just one particular paragraph in this book would have saved us an amount of money best not admitted in print. If you have Knuth on your shelf then there's a good chance that you'll want Hacker's Delight right next to it.
And just in case life is getting too serious, there are some entertaining chapters on prime numbers and Hilbert curves, written so compellingly that you can't stop reading until the end.
Highly recommended. If this book relates to the kind of work you do, then don't leave home without it.

Excellent Catalog of Techniques
I feel compelled to point out that this book is _not_ a few things: It's not a book that teaches you how to break into computers, or crack codes. It's also not the kind of book that teaches you how to do something which you don't know how to do.

This book is a collection of tricks that show the reader better ways to do things they already know how to do. And it's also a book that can give the reader insight into different approaches and mechanisms for solving problems.

Computer programmers translate their ideas and requirements into any of several computer languages. Those expressions are limited by the language the programmer is using, and maybe even the machine the programmer is targeting. But there is a wide continum of expressions that result in the same -- hopefully correct -- results. Choosing the most efficient, and most elegant, expression to some is "real" hacking.

This book is for real hackers. It's a great collection of tricks for performing usually simple operations in an elegant way. What's elegant? Well, elegant is efficeint. If there's a side-effect of an elegant operation, it turns out that side-effect is probably useful and not simply discarded.

This book catalogs insights into concrete binary math, shortcuts derived from different boolean operators, and even approaches some interesting numerical analysis problems.

If you already know how to write software, and you already know you want to find faster or more efficient ways to check for overflows on integers, divide nubmers, count bits, search for binary patterns, or do other twiddling, then this book is for you.

If the application of such techniques doesn't seem important to you, then this book probably isn't going to be of interest to you.