Slashdot Mirror
Hacker's Delight
Hacker's Delight is an impressive compendium of clever tricks for programmers. Warren concentrates on micro-optimizations -- few of the tricks in this book operate on more than 3 or 4 words of memory -- and he displays an impressive knowledge of diverse computer systems in the process.
Who Should Read This Book
Hacker's Delight is hardcore in its presentation and subject matter. I would not recommend this for a beginning programmer -- to fully understand the material requires at least some knowledge of concepts such as Assembly and Machine languages. However, anyone who writes performance-critical software should read this book, even if they do not plan to write Assembly code, both to learn the tricks given, and to learn the concepts behind them.
What's Good
The book is organized into chapters where Warren presents related tricks. In each chapter, he presents a few tricks which perform related tasks -- for example, in Chapter 3, he presents tricks for rounding (up or down) to the next power of 2, rounding to a multiple of a known power of 2, and detecting power-of-2 boundary crossings (i.e., checking for page faults). For each trick, he discusses why it works, whether the technique is generally applicable, related tricks which might be better in specific situations, and where a trick might be used in the real world.
Warren keeps his discussion architecture-neutral, while noting optimizations and problems for specific architectures for specific tricks -- in the process, he displays a vast array of knowledge about specific processors, from 1960's mainframes to x86, MIPS, PPC, Alpha, and others. He also skims the surface of hardware-design issues in a few places -- for example, he devotes a page or two to explaining why computers use base 2 for arithmetic, and why this is the most efficient choice.
What's Bad
This is an extremely dense book, and there are sections which are difficult to understand. Furthermore, there are many tricks which, while interesting, would be difficult to apply to real-world applications, and use of these tricks does violate the Keep It Simple, Clock Cycles Are Cheap And Someone May Have To Understand Your Code philosophy which is harped upon so heavily (not without reason) in modern software design. However, someone writing a compiler or high-performance code may feel that the benefit outweighs the potential risk.
The Summary
If you want a better understanding of the hardware on which your code runs, or you need to squeeze clock cycles, or you just enjoy seeing clever tricks, this is an excellent book. If you primarily use high-level languages such as VB, perl, python, etc., this may not be the right book for you. Be prepared for very dense material.
You can purchase Hacker's Delight from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Almost as interesting as those lovely discrete math textbooks were. This sounds more like 'Optimizer's Delight.'
To be honest, 'Hacker's Delight' sounded more like a cookbook title.
--------
Free your mind.
Furthermore, there are many tricks which, while interesting, would be difficult to apply to real-world applications.
Maybe you should break open the old CS textbook instead. IMO, learning general principles would be a much better use of your time.
I know the author well. Here's some background for you slashdotters who may doubt his expertise:
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.
...is the exact oposite of afternoon delight, I would imagine.
I said a hip, hop, hippy, hippy to the hip hop hacking you don't stop a hacking until the bang bin boogie said backslash the boogie to the rhythm of the boogity beat..
What you hear is not a test, I'm hacking to the beat. And me, the compiler, and my code are gonna start to move your screen.
See, I am das MB and I'd like to say hello
To the linux loners and the mac fairys and the losers on windows.
But first I gotta..bang slash bin slash P E R L said hack kernel yes hack hack the kernel until the whole machine runs like hell.
Proper.
Hey freaks: now you're ju
Sounds like he knows his stuff. The world needs more asm-aware programmers. High level languages and all the trickery that is "keep the source simple, waste the abundant cycles" and all are important things. The problem IMHO is that these are techniques to be applied by a fully-fledged programmer, who is capable of doing it the hard way in C or even asm - but too many modern programmers have only ever know the world of OO languages. The Leaky Abstractions paper applies here too.
11*43+456^2
If you like this topic you may well appreciate this Assembly Language Gems Page
It's a little biased towards x86 assembly, but there are some neat tricks there, and some stunningly lovely code.
I got this a couple of months ago and found it rather good -- If you are looking to shave a couple of cycles off you implementation of integer logarithms then have a look at it. I'd agree with the reviewer that it is rather dense, and you'll need to be numerate (graduate maths or C/S) to understand the algorithms, but not to find it useful. There are also quite a few amusing anecdotes from the author's time at IBM. Worth the cover price.
Jim Green
I am pleased to see the correct use of the term "hacker". Now if we could just work on the folks at CNN...
I noticed this book at the local Barnes and Noble. Unfortuately, it was (and still is) mis-catagorized and firmly stuck in the "Security" area of the technical / computer section.
Now I know that I'm toying with the usual hacker/cracker jihad. None the less, it seems the definition of "hacker" associated with secuirty is so engrained in to society that it manages to overcome even the content of the book itself. I would have thought the B&N folks, being in the book profession, would manage to catch this. Judging a book by its cover and all that (makes me wonder where a book called 'Pinky Fuzzy Bunnies' that studies furry erotica would land).
Of course, B&N are not the definitive measure of language. Where they stick a book doesn't go much beyond acknowledging one use of our much-flamed word. It doesn't negate the history of the word nor offer final proof of its popular definition. But it does show the power of that popular definition despite the obvious intent of the book's author.
Be it for good or not - there it is.
That's not to say that I don't enjoy reading about these clever things; there is a lot to be learned by studying this stuff. But implementing them is usually a mistake these days, if for no other reason than because there's already a portable way to do it which is probably more efficient. To go back to the Duff's Device example, almost all compilers will implement loop unrolling already. And that's a C-language trick, supposedly already a high-level language. Note I said supposedly! :-)
manipulate computers into doing more work on their part with less work on yours
To paraphrase the great Terry Pratchet: "Beware labour saving devices which are smaller than their manuals".
Ingrate! If it weren't for me, it'd be running gene sequences all day and night. Computers have no sense of perspective.
For 99% of people, these kinds of unreadable but "neat" optimizations are going to have no impact on execution time whatsoever. Good algorithm design and efficient architecture -- and yes, optimization, once you've profiled and located a bottleneck -- are worth far more than stupid bit shifting tricks, and your code will actually end up maintainable. If you follow the advice in this book, you're liable to produce code that looks like the Linux kernel.
Karma: Good (despite my invention of the Karma: sig)
In some cases, this may be true, but not always. If you want to increment a multiple-precision value, the textbook method is while the "cute trick" method is
The textbook method takes a while to recognize, just because it's very similar to many other loops; but the second is distinctive and can be recognized immediately. If I'm maintaining someon else's code, I'd much prefer to see the second.
Tarsnap: Online backups for the truly paranoid
Modest doubt is called the beacon of the wise. - William Shakespeare
3313 bytes in body
I almost thought that was 31337 or something!
Well, I remember when I was reading a book about assembler they expressed it beautifully by saying that if school taught kids binary numbers instead of the decimal system, the entire mathematics syllabus could be taught in a couple of months with time to spare.
Binary maths make many integer operations ridiculously simple, and while the fact that it's cheaper and more feasible to detect 2 states than 10 is true, there's also a certain simplicity that you can get to by coding everything with binary logical gates which wouldn't quite be there if you used some sort of decimal logical gates...
Basically, binary arithmetic is really simple so can be optimized really well and is much more universal, in the wider philosophical sense, than decimal arithmetic. Everything in the universe seems to revolve around a binary concept, rather than a decimal one... matter/antimatter, existence/non-existence, quantum spin states, etc.
Daniel
Carpe Diem
Here's a sample:
HACKMEMI've not read the book yet, but I do have a general worry, that optimisation isn't always done in the right context or for the right reasons. Code that runs faster in a small test program can break when part of a larger program (by thrashing the cache for example). What's the point of optimising something that's seldom invoked, in other words, always ask an enthusiastic optimiser to show you their profiling results.
My favourite hacks are Jim Blinn's floating point tricks - 10% accurate square roots and reciprocals that blow away a floating point unit and are just what you need in graphics and games.
Don't worry bud, I agree with you. That's funny shit. :) I'll stand by your side. Bring it on, you mod-punks with no sense of humor!
You know, the post was offtopic but funny... shouldn't that average out to "Neutral +0"?
-FF
SQUEAK, the Death of Rats explained.
The reviewer speaks truth about this book. It is quite dense and, in many cases, violates the "Code should be easily decoded by future programmers" rule.
I got this book for Christmas because I specifically asked for it. My mom was a bit put off by the title, though. The title refers to the original definition of "hacker," so don't get excited if you're all about computer security. There's nothing in there for you.
One of my favorite concepts in this book is the author's use of non-breaking code. As many of you know, the mechanism for sending instructions to the CPU requires a bit of quasi-premonition. Riddle your code with many if-, while-, and (the hideous) goto-statements, and you will end up with slow code due to the seemingly random jumps inside memory. Use some of the methods in this book, however, and you will end up with more efficient code in the longrun. Need I remind you of the speedup generated when you use non-breaking code within a lengthy while loop?
IWARS.
People, in general, disappoint me. Politicians even more so.
aimed more at getting more features then having a fast, stable program
As I understand it, "stable" is kind of in opposition to both "fast" and "features". The reviewer's point is that super-optimized code tends to have strange tricks in it that are difficult to read and understand. That makes the code hard to maintain and increases the likelihood of bugs, so performance tweaking isn't a great idea unless speed is really important to an application.
Do the math. As a first approximation, optimization of software running on a desktop machine has to save the users as much or more time than it takes the developer to produce and support the optimization. This means that if the statements you are optimizing will not be executed hundreds of millions of times, it's not worth worrying about. OTOH, if MS could shave one second off the start-up time for Word or IE, that would be worth tens of millions of dollars annually in additional productivity for the US economy overall.
I have come to despise the whole hacker culture based on the use of the sort of tricks the review illustrated. I comment my code like crazy, avoid confusing booleans, put null on the lhs of code, etc.
But unfortunately, the other people on my team do none of that, and it would only be more painful if they were trying the sort of stunts this book focuses on.
Believe with me, my saplings.