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Edsger Wybe Dijkstra: 1930-2002
Order writes "Edsger Wybe Dijkstra, one of the founding fathers of computer science and the author of the famous "Go To Considered Harmful", has died on Aug. 6, 2002 after a long struggle with cancer."
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After reading this article, I think we all need to pause for a minute, and consider the insight of this simple observation.
Add his definition of things human minds are geared to list: static relationships. It's perfectly in line with Dawkins statement that human minds are designed to comprehend things roughly human-sized moving at roughly human-speeds.
I keep forgetting how long people have been programming. Think about how many people using GOTO there were back in 1968. Probably only a few thousand. Crazy.
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A pity he's gone.
Any service that uses pathfinding algorithms (such as MapQuest) should pay their respest.
I'll bet he gets there by the shortest path.
Some links from my article that slashdot rejected some hours ago: the University of Texas announcement has a list of his awards and discoveries. (He taught at UT.) A brief paper (in PDF, it's scanned from a handwritten paper for CACM if I recall) shows his brilliant, clear, and concise methods of thought and writing.
If you ever used an application that made use of shortest-path searching -- say, any real-time strategy game -- then you owe this man a debt of gratitude.
You cannot apply a technological solution to a sociological problem. (Edwards' Law)
Dijkstra was very good at producing quotable remarks; in addition to his comment about computers, thought, submarines, and swimming (RTFA), he made the following remark about computer science:
"Computer science is as much about computers as astronomy is about telescopes."
Tarsnap: Online backups for the truly paranoid
I found the quotes here: http://www.cse.iitb.ac.in:8000/~rkj/dijkstraquotes .html I paste them here in full to counter the slashdot effect.
:-) -->
Some Quotes of Edsger Dijkstra
"Always design your programs as a member of a whole family of programs, including those that are likely to succeed it"
"Separate Concerns"
"A Programming Language is a tool that has profound influence on our thinking habits"
"The competent programmer is fully aware of the strictly limited size of his own skull; therefore he approaches the programming task in full humility, and among other things he avoids clever tricks like the plague" (from 1972 Turing Award Lecture)
"Progress is possible only if we train ourselves to think about programs without thinking of them as pieces of executable code"
"Program testing can best show the presence of errors but never their absence"
"I mean, if 10 years from now, when you are doing something quick and dirty, you suddenly visualize that I am looking over your shoulders and say to yourself, "Dijkstra would not have liked this", well that would be enough immortality for me"
And then my quote
Use Adsense for Charity
...he is not going to need his forks anymore and the other guys are finally getting to eat?
seriously though, i think dijkstra will be remembered as long as there is the need to prevent race conditions... which in my eyes is quite an accomplishment.
-strangeloop
It's a shame that /. seems to think "Go To Considered Harmful" is Dijkstra's signature achievement. He was profoundly influential in developing the theory of operating systems. He was one of the first proponents of layered design. He also did pioneering work in mutual exclusion (IIRC, he invented semaphores) and deadlock. In short, he is responsible for a lot of the fundamental concepts that we use to build complex systems today.
In today's computer world, dominated more by marketing folks more than the technicians, I wonder how many people have heard of this man. It is sad that in the last decade of so, CEOs like Bill Gates and Jeff Bezos have gained so much public recognition while people Dijkstra languish in relative anonymity.
A few weeks ago, there was a post in /. about Knuth. I was surprised to see many ask who he was!
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For those of us who have chosen the fields of computer science & engineering as our professions, this is a time to reflect and realize just how lucky we are.
We're getting in on the ground floor. The folks who were there in the VERY BEGINNING of our field are still around to teach us something. We need to remember just how privileged we are to have these fantastic people with us to "pass the torch" so to speak.
Look at how far the medical field has come in its history. Or chemistry. Or physics. And these are just scientific professions.
Think about other things, like teaching or agriculture.
We're the next group to advance CS/E. We've got to adopt these folks as our mentors and learn all we can from them.
Not just _how_ their stuff works, but _why_ they did it. Fundamental practices 30 years ago are as fundamental today as they were then.
"Those who fail to learn from their past tend to repeat it."
RIP, Mr. Dijkstra. And thanks for being such a great mentor.
--NBVB
I like spaghetti code. I grew up on AppleSoft Basic and GW-Basic (thank you microsoft).
I read books I picked up from the library for free which showed Basic programs threaded back and forth in sequence, for no apparent reason, and like this sentence, confusing the heck out of me. I saw it as a challenge. I also loved condition gotos'. They were evil.
Gosub? Bah. They ran out of memory too much. Because I hadn't the discipline to Return before I Goto'd out of the subroutine. So I used Goto's to simulate procedures. I also eventually used Goto's in a way that I would eventually learn is like structured programming. Set some variables, goto here, do stuff, goto back, set the same variables something else, goto here, do stuff, maybe goto back. Or it would be the end of the program.
Then I got my first C book. I still haven't got the hang of this language. Before the book even mentions "goto" it gives me a lecture on how awful goto's are and that they can produce spaghetti code. But I *like* spaghetti code. And whats with these labels? Line numbers were so much cooler. But I took the man's advice, I used functions.
But Basic spoiled me. I was never an effective programmer since. It wasn't long after I learned of structured programming that I got my first book on C++ and was introduced to object-oriented programming. Now, for someone using structured techniques for a couple years, the need for objects seemed to make sense. But I was lost in a sea of hierarchial classes and virtual methods.
When I first went on the internet, I started learning all kinds of crazy languages, hoping some of them would be simpler. And there were many. Except for forth and common lisp. Except for ML and Smalltalk. So I am still toying with scheme as I speak, still trying to figure out what exactly the difference between a recursive and iterative process is.
Eventually, I'll figure out how to write spaghetti code in this otherwise clean and elegant language too. Continuations sound promising, from what it sounds like.
I wish the best of Dijkstra--hope he rests in peace. Honestly, I've never heard of him until this post to slashdot.
But maybe it is slightly better for him not to know that some of us never learn.
Non-Linux Penguins ?
Two chapters from one of Dijkstra's books improved my program correctness by an order of magnitude, and this was after I had fully digested Bertrand Meyer on programming by contract. His notion of guards is the number one item on my top ten list of everything I know about writing correct code.
Just looking at his U texaspublication list is an awesome (pre-1990s meaning) experience. Let your eyes scan it, as they would the Grand Canyon. Then wander around the UTexas site, where many publications are online, and start reading. You'll be a better person for it. And you may experience a thrill of understanding, when you see that his hands hold up so much of today's code, as Shakespeare's hands hold up so much of the language and common experience of the English world.
To get a feel for the span of his life's work, consider his thesis title, "Communications with an automatic computer." The word "automatic" was necessary then, to distinguish it from a person with a calculator. The machine he used in his thesis? It had a 32K memory unit. He divided this into what he called "living" and "dead" memory.
Let's hope that his memory will be of the living variety.
To a man I never shall meet, thank you.
This man contributed many great ideas to our field. The sad thing is how many programmers are still in ignorance of them, even now. You did great things, Mr. Dijkstra, and will be sorely missed. I just hope we're still allowed to have generic computing devices in ten years' time, so we can continue to refine and develop the revolutionary ideas you left us with.
When I was just fresh out of college back in 1978, a collegue of mine who had been on Dijstras circulation list gave me a large stack of photocopied papers from Dijstra...all written in his own handwriting because he liked to invent his own symbols and found typewriters too limiting. I was working for Philips Research at the time - and I suppose Dijstra was working at Philip's "Math Center" in Eindhoven, Holland.
:-)
I've kept a whole boxful of his papers over the years - just because they are so fascinating to browse.
He invented his own programming language for expressing algorithms - but doesn't seem ever to have written a compiler for it. He refers to algorithms his mother came up with...almost every document has something interesting like that.
The notes are written in the most perfect handwriting you've ever seen.
They could have been printed - they are that precise. Then, one of them out of the blue seems to have been written in someone else's handwriting - it's just as amazingly neat though and when you get to the end of it, it says something like: Apologies for the poor handwriting in this note, but my left hand could use some practice.
These cannot be stored as text files without losing most of their historical interest. Maybe I should spend an evening or two to scan them and put them online. There could be no more fitting tribute to the man.
www.sjbaker.org
Although Edsger is remembered for the article on the
goto, his development of the stack model was an
evolutionary leap in the development of computers.
Every computer made today embodies his model.
Interrupt handling, recursion, reentrant
programming, multi-programming, multi-processing,
virtual memory all come out of Edsger's model.
I had the great fortune to work on a Burroughs B5500
and later the first B6500 that made it out of
manufacturing. This entire series of computers
was based on Edsger's model and his Algol 60 compiler.
Tony Hoare may have put it best when he quipped
"Algol is an improvement over all its successors".
Certainly Edsger was an improvement over most of
his successors.
Jim Tarvid
I took it in 1992. He was an amazing professor--as eccentric as you'd imagine him to be. I remember him once asking us if any of us knew of a good place to get his worn Birkenstocks repaired.
He was the person who first made me realize--at a visceral level--that clear thought is as important in a program as clear prose is in writing a novel.
After the final exam (conducted verbally, one-on-one, at his home), he asked me what one thing I would most take away from his class. He seemed to consider my answer to this question more important than my performance on the test itself. I told him what the above about literature and programming. He nodded, thought for a bit, and said 'Very good. Can I offer you some tea before you go?'.
I got an A, so I guess he liked my answer.
Honestly, I think the biggest crisis in software development is the "function follows form" problem. People are choosing implementation parameters before the problem is even designed!
:) These are just my personal feelings about software development today ........
;)
It's the "I don't know what it is we're going to do exactly, but I know it'll be done in Java" problem.
The second-biggest crisis in software development today is the bloat problem, IMO. The fact that hardware speeds & memory capacities are following Moore's Law is no reason for us to bloat the code so badly.
Re-writing things that used to function just fine in a new paradigm just for the sake of rewriting it is asinine!
The concept of "Webifying" everything is just silly. Whoever thinks that stateful tasks should be done with a stateless protocol (HTTP) is insane!
Anyway, enough ranting.
And you are completely correct. We need to learn not only the lessons of our mentors, but their mistakes too. Mistakes like C shouldn't ever be repeated...
Oh, did I just say that?
Sorry, I'm letting my personal feelings out again
--NBVB
It's bad to think of Dijstra only in terms of *one* memorable thing he did...but since we're doing that anyway...
...processLeafNode... ; ;
When I learned to program in the early '70s, our lecturer told us that if we used even *one* 'goto' in our work, we'd score zero for the entire assignment.
I've been programming for ~30 years now and never felt the slightest need to use one in a high level language since that day.
I strongly disagree about recursion though. Used properly, it's *very* readable:
void binaryTree::walk_binary_tree ( void )
{
if ( isALeafNode () )
else
{
leftBranch -> walk_binary_tree ()
rightBranch -> walk_binary_tree ()
}
}
Try writing that more cleanly without recursion!
(NOTE: You may be able to make it faster or more memory efficient without recursion though).
The art of reading and writing recursive programs is to try to forget that they are recursive.
I think to myself:
"In order to walk this tree, I walk the two child branches
- hmmm - I have a function to walk trees - I'll just use it
and assume it'll do what it's told."
The fact that the routine you are calling is also the routine you are currently writing just doesn't matter in most cases.
www.sjbaker.org
At the UTexas EWD archive.
Moderators: This is one of those posts where I say screw karma. Mod me to redundant hell if you wish, it just doesn't matter.
This is an extremely sad day for computer science. There is hardly a field in CS that Dijkstra's work didn't touch. His work can be seen everywhere we use computers.
Personally, this is an extremely sad day for me as well. Although I never met the man or saw him speak (now one of my greatest regrets), being in college, he's my equivalent of a Joe DiMaggio or a Ted Williams. This man was a hero and an inspiration to me.
Sometimes it really pisses me off that we show such public sorrow for sports figures who pass away like Ted Williams who for the most part didn't do a damn thing to really and truly improve our lives (granted Ted Williams was a marine and fighter pilot but that's not why most people were mourning him). This man greatly and directly contributed to a vast improvement of our quality of life as human beings. His obituary will be a foot note and page Z-42 of the NY Times and Washington Post but when celebrities die, they're front and center on page 1. It makes me sick.
That's my 2 cents and I'm not giving any damn change. >:o
If you know him for nothing else, Dijkstra's Semaphores (aka P and V operators) are a fundamental construct in pretty much any parallel processing environment. Many CPU's have Dijkstra's semephores implemented at the hardware level. It's hard to think of anyone else who has such a fundamental construct named after them. OK, maybe 'Booleans' and the long defunct "Hollerith String".
www.sjbaker.org
This is speculation, but I would guess that he's speaking of the first couple chapters of "A Discipline of Programming".
Dijkstra's mindset is not for everyone. It's the mindset of a computer scientist who wants to have confidence in his code, confidence that does not come from ego (I am aswome, therefor my code never stinks).
I think the ugly hack has it's place. After all, breaking a window is usualy a bad way to accomplish something, but if the context is you're trapped in a burning house, it's more likely a good move. Bodgeing it out has a similar context, but 99% of the people who don't value clean, well considered code are not in that context. And of the 1% who are, I would bet many of them are in that burning house because someone before them didn't value clean and well considered code.
Except I thought good compilers these days are able to recognize a sitation like this an inline the function?
Anyone have good profiling tools available for the really good compilers?
Let's not forget this bit of fun. We can banish goto forever now that someone finally invented
comefrom.
Those who actually read the linux kernel source codem probably already knew Dijkstra and his god-like powers in the computer-sciences.
But for those who put their nose in there and juts read the comments, there are some references
Fr example: drivers/scsi/NCR5380.c
echo '[q]sa[ln0=aln80~Psnlbx]16isb572CCB9AE9DB03273snlbxq' |dc
It is sad that in the last decade of so, CEOs like Bill Gates and Jeff Bezos have gained so much public recognition while people Dijkstra languish in relative anonymity.
and in his time, whom do you think was more famous, Newton or his King/Queen ? Lagrange or whatever Louie ruled then ?
True metal survives the acid test of time. The ornamentations, the hype-sellers, the gates'es and Bezos'es, will be forgotten by everyone (except historians) by the next century.
Dijkstra's shortest-path algorithm and other works will be remembered in centuries to come.
Working for necessity's mother.
I received my computer science degree from the University of Texas, where Dr. Dijkstra taught before retiring. I never took the undergraduate class he offered (I was kind of intimidated at the time), but the professor who taught my Software Engineering class had him come in to lecture one day.
This software engineering class was very pragmatic, emphasizing methodical design, implentation, and testing. As I recall, Dr. Dijkstra gave his lecture near the end of our semester, by which time we had been heavily involved in something resembling a team development evironment for a few months.. There was a very corporate feeling to our regimen of meetings and reports.
So one day we all go to the faculty lounge to hear the esteemed professor speak. He comes in the door of the lounge appearing to me most unlike the kind of man who could write so forcefully about programming, dressed in shorts and a tee-shirt with a distinctly old-grandfather look on his face.
In his very soft-spoken manner, he told us that he beleived that the main problem with programmers was a lack of rigor. People were so concerned with coding and testing that they never learned how to write something correctly the first time. He asked us to prove the correctness of the code for a binary search and spent the next half-hour proceeding glumly as we slowly worked through the process with him.
I got the impression we were a vaguely dissapointing group of students who he could tell were not convinced of the validity of his approach. It wasn't even a bitter dissapointment, though. I felt as though he was someone who had totally convinced himself that he knew how to make the world a better place, but that noone was listening.
He answered our questions about "gotos considered harmful" (it was his editor's idea to give it the cute title) with what I considered obvious patience. He talked about how he really only was able to keep up on the research that people referred to him these days. And then the lecture was over.
Our professor and Dr. Dijkstra were good friends, and I hung around after class talking with them about computer science and Dijksta's past. I ended up in his office after a while and we chatted about the current state of the industry as he saw it, why he really liked Texas, and so on. He was so intelligent in his conversation--asked so many probling questions--that by the time I was done I felt both touched and exhausted. He put on his cowboy hat and walked out of the office with me and headed off to his next appointment.
That was the last time I saw Esdgar Dijkstra--the only real time I ever talked to him. But I feel that the world has lost a quiet crusader, and I feel a tug in my heart thinking about this old dean of computer science with his cowboy hat.
-- Have you ever imagined a world with no hypothetical situations?
It is practically impossible to teach good programming style to students that have had prior exposure to BASIC; as potential programmers they are mentally mutilated beyond hope of regeneration.
APL is a mistake, carried through to perfection. It is the language of the future for the programming techniques of the past: it creates a new generation of coding bums.
The use of COBOL cripples the mind; its teaching should, therefore, be regarded as a criminal offence.
When FORTRAN has been called an infantile disorder, PL/I, with its growth characteristics of a dangerous tumor, could turn out to be a fatal disease.
COBOL is for morons.
With respect to COBOL you can really do only one of two things: fight the disease or pretend that it does not exist.
The question of whether computers can think is like the question of whether submarines can swim.
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