you're trying to stir up some controversy where there isn't any.
By asking you to explain or expand on your statements? You alluded to some objections you had to Drexler and I asked you for more details. I'd hardly call this "stirring up controversy."
Saying that "Drexler isn't ahead of his time" is not the same thing as saying "everything he has ever done is rubbish". I said the former, and I'd appreciate it if you stopped acting as if I said the latter.
What you said was (and I quote):
Engines of Creation[...] wasn't a very good book, if memory serves.
Nanosystems isn't that great either.
There's nothing brilliant about what he does.
The only change he's made to the scientific community is flooded the field with scientists and engineers who use his media hype to get funding for poorly conducted research.
Engines of Creation were a lot of fun... when I was in middle school. If you want to understand nanotech, go read some real science.
I see Drexler's work as detrimental to the scientific community
most if his ideas aren't original
the way he markets them harms the people he wants to assist
You mention Feynman's talk, "There's Plenty of Room at the Bottom"; it seems you've not actually read it though. Feynman explicitly mentions building things at that level, and created a prize for the first people to build particular nanostructures (granted, some reprints of the talk might not include the prize information).
As a matter of fact, I have read it. (There's a copy on the web for anyone who hasn't.) The talk was mostly about something like modern semiconductors and what we currently call MEMS, including the prize you mentioned.
If you read it, you see that Feynman saying things such as (and again, I quote):
Why can't we make them very small, make them of little wires, little elements---and by little, I mean little. For instance, the wires should be 10 or 100 atoms in diameter, and the circuits should be a few thousand angstroms across.
If I make the thing too small, I have to worry about the size of the atoms
Plastics and glass and things of this amorphous nature are very much more homogeneous, and so we would have to make our machines out of such materials.
We can make flats by rubbing unflat surfaces in triplicates together---in three pairs---and the flats then become flatter than the thing you started with. Thus, it is not impossible to improve precision on a small scale by the correct operations.
Only in a few paragraphs at the end does he mention the possibility of building atomically precise structures, and then only to say that he thinks it might be done.
If you fail to understand what I'm saying, you're welcome to ask for a clarification rather than assuming the worst.
That is exactly what I did. You made a number of statements and I quoted your statements verbatim, and asked you for examples, clarification, etc.
Logically, there are only a few possibilities:
You think that Drexler is wrong, atomically precise machines are not feasible. In which case, my question is, why do you think this?
You agree that atomically precise machines are feasible, but think that someone else came up with and elaborated the idea first. If so, who?
You think that Drexler is correct, and original, but has mismanaged the presentation of the idea. If so, I would be tempted to agree, while laying more of the blame on Foresight than on Drexler himself. But if this is your position, it's hard to see why you said what you did about his books, originality. etc. Further, it's hard to see why you'd object so strongly to whoever said he was ahead of his time, since (on the premise that you agree that Drexler-style nanotech will someday be a reality) coming up with an idea that will someday be feasible but isn't yet is practically the definition of being "ahead of your time". Thus my assumption that you must hold one of the first two positions.
While making the move from cubicle life to an office I have noticed that my walls are very bare. I went searching for BSD and Linux posters but couldn't find any. IS there not production of these posters or am I looking in the wrong place?
What do you need pre-printed posters for? Just spool out your favourite man/info pages, grab some electrical tape and...ta da!
This type of research would be going on with or without the hype, but because of the hype, a lot of bad research gets funded, and a lot of good research goes unfunded. To say that this man is ahead of his time is to forget that most if his ideas aren't original...
Can you give an example of someone who had previously put forth the argument that atomic scale engineering of the sort that Drexler addresses would be feasible? I know that several people (notably R. P. Feynman) had argued that it should be possible to manipulate matter at this scale, but I don't recall anyone proposing that we could build things to atomic precision. Nor am I aware of anyone who put forth detailed arguments for the advantages and disadvantages of using individual atoms as material for an extension of mechanical engineering.
As a researcher in condensed matter physics, I see Drexler's work as detrimental to the scientific community, largely because it helps popularize a trend and set of buzzwords.
I, on the other hand, don't think the quality of scientific work should be judged by the social reaction to it. (E. O. Wilson, to pick an unrelated example, fomented a great deal of popular noise with his social biology, but I still like his work. Why? Because it makes solid, testable predictions).
So, granting that there are a considerable number of people spouting nonsense and attaching Drexler's name to it (and, as an aside, I find them as annoying as you do), I'll ask you this: what is your scientific objection to nanosystems? Does it make claims that you counter-claim are false or (worse) are unfalsifiable? If so, can you tell me what they are and sketch your reasoning in objecting to them?
If all you are going on is Engines of Creation (or rather, your vague recolection that it wasn't very good) I'd suggest you look into some of Drexler's other work, such as Nanosystems. It's always a bad idea to judge someone by a popularization of their work, even if they wrote it.
Are there any features that restaurants need that your traditional POS system may not include?
You missed the big one: spill proofing.
We addapted a retail POS system for restaurrant use back in the 80's, and at the end of the first trial month about a quarter of the hardware had been killed by the environment. IMHO, it's harsher than outdoors (when was the last time it rained ethanol, carboxilic acid, acetic acid, etc.?) and harsher than many industrial environments (where at least the people get more training).
What a nit. You say riddled and yet you can only name one supposed inconsistency which really is not and it is not even apropos to the question at at hand.
I, on the other hand, would maintain that it is to the point. It was a clear example of the sort of emotional (as opposed to rational) argument you were offering. In particular, your heated tone implies sharp distinctions that all but vanish when examined a little more calmly. They are (I would argue) an artifact not of what you are saying but of how you are saying it. For example, from your last post:
Put bluntly, if you wish to hold up viruses as an example of the frequency of "trojans" in closed source software, then you should make a strong distinction between the virus' very generic attacks and the often far more dangerous and subtle trojan attacks of humans on specific code and installations.
Stripped of all the heat/emotional language, your statement boils down to: "to use viruses as example of trojans you should distiguish virus attacks and trojan attacks." In other words, if I want to say "A is an example of B" I should say "A is not B"--which is not a valid statement about categorical inclusion.
Even if it was true in general, it wouldn't apply in this case since "trojan" is a means of acting ("trojan" code is code that lies hidden inside a seemingly innocent program, and therefore is executed by an unsuspecting user) while "virus" is a means of propogation ("virus" code is code that spreads by using the resources of infected machines to make copies of itself). To put them in opposition is a silly as contrasting "things that swim" with "things that lay eggs".
If I try to guess what your real point is, the best I can come up with is "viruses are easier to detect than trojans, because you can spot them by looking at the binaries instead of digging through the source". While this sounds a little more reasonable on the surface, it is also flawed. Yes, it is easy to spot a virus by compairing an infected binary with an uninfected binary (if you know which one is which). But it would be just as easy to detect a trojaned program by compairing it to an untrojaned copy (again, assuming that one was labled "suspected" and the other was labeled "known good").
As for contrasting open source and closed source (which seems to be the main axe you are grinding), the advantage of open source is that, in the case where you don't have a "known good" copy) it is much easier to find suspicious code by looking at the source than by looking at the binary.
Oh, give me a break. Your post is riddled with misconceptions & logical inconsistancies. For example:
There's a world of difference between a virus that blindly inserts malicious code (e.g., destroy sector 0) into any binary it can get its hands onto and a true trojan that was written for a special purpose by an actual human being.
So, the "true trojan" was written by an "actual human being" whilst the "virus" was written by...what? A tree frog?
No, it was written by an actual human being.
To do what? To "destroy sector 0"? How fast would that spread? Typically, a virus is designed to attach a copy of itself to the binary, producing a composite that contains the original code and cody written by the virus writter, in much the same way that a trojaned program is a composite of code from the same two sources.
And so on.
-- MarkusQ
P.S. You may want to check your sources. A preliminary scan indicates that you may have been trojaned by the MSFUD virus.
...if you were the administrator of an e-mail server, what would you set the maximum size of an incoming email message to be, and what would be the reasoning behind said limit?
I am the administrator of an e-mail server. Our limit is 5Mb. I found that to be a reasonable elbow in the curve between most of our trafic by message count (e.g. Things like "I'm running late...could you hold off processing xxxx for me?" and "No.") and the majority by size (e.g. "Here's a copy of that set of porn CDs I stole"). It only affects legitimate bussiness trafic about once a year (we don't use MS Office, etc.) and it cuts our total storage volume by about 80%.
You seem to be missing the underlying definition of a real-time system...a payroll system that runs on a real-time operating system...would pretty much mean that the only thing that operating system is used for is payroll.
Real-time systems are about priority. A real-time system, hard or soft, will run real-time application without context switches until that process is complete.
Real time problems are problems whose definition includes dependencies on the passage of real time.
Real time systems systems that are used to solve real time problems.
Prohibiting context switches is common in real time systems, since it eliminates one potential source of failures, but it isn't essential (you can get the same results by having a much faster processor, or a pool of processors, etc.) and in any case it isn't a cure-all. If the time constraints are tight enough that your hardware can't meet them, you're still out of luck.
Claiming that payroll isn't a real time problem because you don't need a real time system that eschews context switches to solve it is the same sort of logic as claiming the earth isn't a planet because you don't need some specfic type of telescope to study its surface.
aePrime: We're not talking about human deadlines as time constaints.... For instance, it would not do for a robot arm to be instructed to halt after it had smashed into a car it was building
The only reason that it is unacceptable for the robot arm to be instructed to halt after it has smashed into the car is that the cost of it's doing so is greater than we are willing to accept and still say that the system is working. Consequently, we say that the system fails if it does not meet the constraint. Exactly the same statement may be made of a payroll system (we define the system to have failed if it has not produced the checks by the statutory deadline, posibly adjusted by some margin of safety).
aePrime: Look at this as saying that the process must be given CPU time to insure that it completes within its time constraint. This is not the case for the payroll system. The payroll system does not require all of a CPU's attention.
TheConfusedOne: Real time usually has to do more with interrupting things in order to meet time constraints (hence the pre-emptive kernel patch). That means that when you program something in real time and say this activity has to happen every five seconds then at that five seconds everything else will be interrupted in order for that activity to occur. (There are of course constraints based on internal timing.) A payroll system has no such constraint. While there are deadlines for people to finish or start activities in the system it doesn't pre-empt any activities.
It's a question of the longest time slice a process can tie up the processor compared to the resolution of the hard real-time constraints. As long as a process can't hang the system, the largest time slice is a function of processor speed. Back in the days of slow hardware, we certainly did pre-empt things to run payroll.
You both seem to be thinking that "real-time" means "fast" when in fact it means that the time constraints are specified with regard to the outside world (thus the phrase "real time"). It doesn't matter if we're talking eons or fempto-secconds, as long as we define success or failure in terms of real world, physical time instead of some internal metric such as processor time.
Of course, the challenge is at the edges, dealing with very small time windows, very long up times, and so forth, and thus these are the things you'll hear people talk about. It's the same in any field. You won't find many cookbooks that devote a chapter to boiling rice, but it's still cooking. And payroll processing is still a real-time application.
Your definition of a real-time system is a little too loose. A payroll system is not a real-time system. Sure, the employees might get angry if the payroll is not submitted on time, but a hard real-time system has well-defined fixed time constraints, and guarantees that these critical tasks will be completed on time. A payroll system makes no guarentees.
I have to side with the original poster. Other than scale, there isn't any difference between a payroll system and something you would typically consider "real time". There are "well-defined fixed time constraints" for payroll processing (in the US often defined by state and federal laws). If you do payroll processing, you guarentee (often contractually) that you will meet the constraints.
In both cases, there are time limits expressed in terms of the outside world("real time"), and sufficient consequences if these constraints are not met to define failure to meet the constraints as system failure. The only difference is scale.
How exactly do you people keep changing from casual to smart clothing every time you need to go visit a client? Does your office have a changing room, or something?:-)
So what you're saying is that if you compile the communist manifesto you get out a sendmail binary?
No, I think he's (either) suggesting that you compare the result of compiling the file communist_manifesto.txt with the sendmail binary (but not in any way predicting the results) or (under the more likely assumption that the file does not contain a syntactically valid program) pointing out to us 1) that gcc deletes any preexisting a.out if it is given an invalid source file and 2) you can confirm this by trying to diff it with something, since diff will complain that the file doesn't exist.
He's correct, but I can't help but think that there are easier ways of accomplishing the same thing.
-- MarkusQ
P.S. Ah! I see! It's a clever way of removing a.out if and only if the file communist_manifesto.txt exists and does not contain a syntactically valid program. I'm not sure why you would want to do this, but it is a rather clever hack if you need it.
there has been a steady increase in the level of abstraction they use
So, C is more abstract than LISP? And C# is more abstract than Haskell? Or is this "steady increase" just an artifact of how you choose your examples?
Imagine you are hosting a party. The first person to show up will either be taller than you, or shorter. And (if the people are showing up in a random order) there is a non-zero chance that the next person to show up will either be shorter than both of you, or taller than both of you. As new guests continue to arive, we should expect the height of the tallest person present to go up, and the height of the shortest person present to go down.
I would argue that the same thing is happening with programming languages. We are not just seeing higher and higher level languages, we are also seeing lower and lower level languages (e.g. so-called programable hardware, PLAs, etc.) at the low end. More than anything, we are seeing a steady increase in the number of FORTRANistic languages that dwell somewhere between BASIC and C.
I like monkeys too. Perhaps we should form a school of thought based on them. We could:
Multiply our slashdot ids to get a biggish integer
Find, buy, breed, or steal that many monkeys
Set them down at that many keyboards (or, if we want to be extreme about it, half that many keyboards)
Run the lexical portion of their output though a spelling checker
Publish it as succ(postmedernism)istic insight
???
Profit!
If we wanted to really confuse people, we could systematically supress any references to "fish" or "pizza."
I guess my objection to "it's all good" is the same as my objection to games that start off with a screen that says "You've won!" and segue directly to the closing credits. I haven't even had a chance to waste my time. If "it's all good" then none of it is bad, so there's nothing to do. Thanks for playing. What fun is that?
Rationalist/objectivist science is (by contrast) loads of fun. Almost all of the answers are wrong, and you have to really work at it to get a respectible score.
PostModernism works? Really? And it has produced...what? I can't off the top of my head think of anything useful that has come out of it, can you? I don't even recall much that was particularly entertaining, at least not enough to justify the whole "movement."
Maybe you meant to say "this is why PostModernism doesn't work."
I am a philosophy student with an intense interest in mathematics and programming...Does anyone...have any recommendations for books dealing with any aspect of programming theory?
It sounds like you are looking for Edsger Dijkstra's A Discipline of Programming, which is great fun if you can juggle math, logic, philosophy, and programming (in a non-deterministic language he made up for the book) without getting fixated on any one to the exclusion of the others. He starts with an interesting angle on why we have computers at all, and builds up from there.
So what prevents a more corrupt administration from...
In theory, something called "checks and ballances." It's a key part of our system; it also prevents things like a rogue president declaring war at random, congressmen passing laws which only help their financial backers, or judges ignoring laws to protect their cronies. Since it's so important, we periodically do a live full system test to make sure it's still working.
I think you are missing the point. People (yourself included) act as if Bell's inequality ruled out all hidden variable theories--in the sense that it allows us to make testable predictions and the results of testing these predictions are inconsistant with the hidden variable theories. But it only rules out a rather small subset of the possible hidden variable theories and there are many others (such as the extreme case I described) that it does not rule out.
An analogy to show the flaw in the reasoning:
Albert: I think there may be someone hiding in the closet.
Bell: Like who?
Albert: I don't know. Henri maybe?
Bell: Well let's see...I know that Henri loves "knock-knock" jokes. Nine times out of ten, he bites if you give him the line.
Albert: Let's try it. Goes to the closet, says "knock, knock" and waits.
They repeat this many, many times; no one ever answers "who's there?".
Are they justified in concluding that there is no one in the closet? Obviously not. Does this mean that there is someone in the closet? Again, obviously not. The line of reasoning they are using is not sufficent to answer the general question.
IMHO, invoking a universe's worth of hidden state per particle just because you don't like the idea of a random universe isn't much less silly than that.
I don't recall saying that I believed in one model or another, or that I liked or disliked the idea of a random universe, or that it mattered one way or another what I liked or believed. I'm just objecting to saying that a class of theories has been "ruled out" by an argument that only addresses a small subset of the class.
This is almost exactly what I was about to suggest, except that I would use string taped down at the edges (& pulled tight) instead of sticks. Why? It makes it easier to remove the pictures afterwards. You'll probably want to do the following:
Measure & make light pen marks on the sides/ends of the scanner where you want the strings to be (in case you have to replace them).
Tape the strings down, but not too tightly.
Tape two strips of wood (e.g. rulers) along two adjacent edges, over the strings.
Lap the strings over & tape them to the top of the wood.
Do the same on the other two edges, this time pulling the strings tight enough to "snap"
Make a point to check that your strings haven't moved every hundred scans or so, and periodically check the cut images as well, just to save yourself from plunging ahead with a miscalibrated setup.
This randomness is distinguishable from so-called "hidden variable" interpretations.
Not quite. There's a hidden flaw in the argument against hidden variables; the "proof" subtily begs the question. To see this, imagine that there were a level of "hidden variables" complex enough that each quanta (quark, lepton, what have you) could have as much "state" as the entire universe as-we-know it. With such a system you could predetermine every "interaction" over the course of the whole history of the universe--there wouldn't be any "physics," just a mind bendingly huge collection of scripted motions.
The point being, there's no way we could detect that this was the case...and thus there's know way we can prove that it isn't the case.
Now, we are free to doubt that we live in such a universe (and believe in "truly random events") but this is just a belief, without any science to back it up.
Slashdot Mirror
you're trying to stir up some controversy where there isn't any.
By asking you to explain or expand on your statements? You alluded to some objections you had to Drexler and I asked you for more details. I'd hardly call this "stirring up controversy."
Saying that "Drexler isn't ahead of his time" is not the same thing as saying "everything he has ever done is rubbish". I said the former, and I'd appreciate it if you stopped acting as if I said the latter.
What you said was (and I quote):
You mention Feynman's talk, "There's Plenty of Room at the Bottom"; it seems you've not actually read it though. Feynman explicitly mentions building things at that level, and created a prize for the first people to build particular nanostructures (granted, some reprints of the talk might not include the prize information).
As a matter of fact, I have read it. (There's a copy on the web for anyone who hasn't.) The talk was mostly about something like modern semiconductors and what we currently call MEMS, including the prize you mentioned.
If you read it, you see that Feynman saying things such as (and again, I quote):
Only in a few paragraphs at the end does he mention the possibility of building atomically precise structures, and then only to say that he thinks it might be done.If you fail to understand what I'm saying, you're welcome to ask for a clarification rather than assuming the worst.
That is exactly what I did. You made a number of statements and I quoted your statements verbatim, and asked you for examples, clarification, etc.
Logically, there are only a few possibilities:
- You think that Drexler is wrong, atomically precise machines are not feasible. In which case, my question is, why do you think this?
- You agree that atomically precise machines are feasible, but think that someone else came up with and elaborated the idea first. If so, who?
- You think that Drexler is correct, and original, but has mismanaged the presentation of the idea. If so, I would be tempted to agree, while laying more of the blame on Foresight than on Drexler himself. But if this is your position, it's hard to see why you said what you did about his books, originality. etc. Further, it's hard to see why you'd object so strongly to whoever said he was ahead of his time, since (on the premise that you agree that Drexler-style nanotech will someday be a reality) coming up with an idea that will someday be feasible but isn't yet is practically the definition of being "ahead of your time". Thus my assumption that you must hold one of the first two positions.
-- MarkusQWhile making the move from cubicle life to an office I have noticed that my walls are very bare. I went searching for BSD and Linux posters but couldn't find any. IS there not production of these posters or am I looking in the wrong place?
What do you need pre-printed posters for? Just spool out your favourite man/info pages, grab some electrical tape and...ta da!
-- MarkusQ
This type of research would be going on with or without the hype, but because of the hype, a lot of bad research gets funded, and a lot of good research goes unfunded. To say that this man is ahead of his time is to forget that most if his ideas aren't original...
Can you give an example of someone who had previously put forth the argument that atomic scale engineering of the sort that Drexler addresses would be feasible? I know that several people (notably R. P. Feynman) had argued that it should be possible to manipulate matter at this scale, but I don't recall anyone proposing that we could build things to atomic precision. Nor am I aware of anyone who put forth detailed arguments for the advantages and disadvantages of using individual atoms as material for an extension of mechanical engineering.
As a researcher in condensed matter physics, I see Drexler's work as detrimental to the scientific community, largely because it helps popularize a trend and set of buzzwords.
I, on the other hand, don't think the quality of scientific work should be judged by the social reaction to it. (E. O. Wilson, to pick an unrelated example, fomented a great deal of popular noise with his social biology, but I still like his work. Why? Because it makes solid, testable predictions).
So, granting that there are a considerable number of people spouting nonsense and attaching Drexler's name to it (and, as an aside, I find them as annoying as you do), I'll ask you this: what is your scientific objection to nanosystems? Does it make claims that you counter-claim are false or (worse) are unfalsifiable? If so, can you tell me what they are and sketch your reasoning in objecting to them?
-- MarkusQ
Dear Sadly Misinformed --
If all you are going on is Engines of Creation (or rather, your vague recolection that it wasn't very good) I'd suggest you look into some of Drexler's other work, such as Nanosystems. It's always a bad idea to judge someone by a popularization of their work, even if they wrote it.
-- MarkusQ
The samba team have released 2.2.7 following the discovery of a secureity hole in versions 2.2.2 to 2.2.6 that could lead to remote root access.
So, basically, they're vacillating on the question of full SMB compatibility?
-- MarkusQ
You missed the big one: spill proofing.
We addapted a retail POS system for restaurrant use back in the 80's, and at the end of the first trial month about a quarter of the hardware had been killed by the environment. IMHO, it's harsher than outdoors (when was the last time it rained ethanol, carboxilic acid, acetic acid, etc.?) and harsher than many industrial environments (where at least the people get more training).
-- MarkusQ
I had a Northstar (8080) with a cherrywood case. It was sweet (*sigh*). 2 MHz, and 32k of RAM...what a great machine.
-- MarkusQ (waxing nostalgic)
What a nit. You say riddled and yet you can only name one supposed inconsistency which really is not and it is not even apropos to the question at at hand.
I, on the other hand, would maintain that it is to the point. It was a clear example of the sort of emotional (as opposed to rational) argument you were offering. In particular, your heated tone implies sharp distinctions that all but vanish when examined a little more calmly. They are (I would argue) an artifact not of what you are saying but of how you are saying it. For example, from your last post:
Put bluntly, if you wish to hold up viruses as an example of the frequency of "trojans" in closed source software, then you should make a strong distinction between the virus' very generic attacks and the often far more dangerous and subtle trojan attacks of humans on specific code and installations.
-- MarkusQ
Oh give me a break.
Oh, give me a break. Your post is riddled with misconceptions & logical inconsistancies. For example:
There's a world of difference between a virus that blindly inserts malicious code (e.g., destroy sector 0) into any binary it can get its hands onto and a true trojan that was written for a special purpose by an actual human being.
So, the "true trojan" was written by an "actual human being" whilst the "virus" was written by...what? A tree frog?
No, it was written by an actual human being.
To do what? To "destroy sector 0"? How fast would that spread? Typically, a virus is designed to attach a copy of itself to the binary, producing a composite that contains the original code and cody written by the virus writter, in much the same way that a trojaned program is a composite of code from the same two sources.
And so on.
-- MarkusQ
P.S. You may want to check your sources. A preliminary scan indicates that you may have been trojaned by the MSFUD virus.
if this star was located as far away as the moon, it could demag floppy disks
Yet another reason I'm glad I stayed with paper tape.
-- MarkusQ
I am the administrator of an e-mail server. Our limit is 5Mb. I found that to be a reasonable elbow in the curve between most of our trafic by message count (e.g. Things like "I'm running late...could you hold off processing xxxx for me?" and "No.") and the majority by size (e.g. "Here's a copy of that set of porn CDs I stole"). It only affects legitimate bussiness trafic about once a year (we don't use MS Office, etc.) and it cuts our total storage volume by about 80%.
-- MarkusQ
Real time problems are problems whose definition includes dependencies on the passage of real time.
Real time systems systems that are used to solve real time problems.
Prohibiting context switches is common in real time systems, since it eliminates one potential source of failures, but it isn't essential (you can get the same results by having a much faster processor, or a pool of processors, etc.) and in any case it isn't a cure-all. If the time constraints are tight enough that your hardware can't meet them, you're still out of luck.
Claiming that payroll isn't a real time problem because you don't need a real time system that eschews context switches to solve it is the same sort of logic as claiming the earth isn't a planet because you don't need some specfic type of telescope to study its surface.
-- MarkusQ
See my response to aePrime.
--MarkusQ
aePrime: We're not talking about human deadlines as time constaints.
The only reason that it is unacceptable for the robot arm to be instructed to halt after it has smashed into the car is that the cost of it's doing so is greater than we are willing to accept and still say that the system is working. Consequently, we say that the system fails if it does not meet the constraint. Exactly the same statement may be made of a payroll system (we define the system to have failed if it has not produced the checks by the statutory deadline, posibly adjusted by some margin of safety).
aePrime: Look at this as saying that the process must be given CPU time to insure that it completes within its time constraint. This is not the case for the payroll system. The payroll system does not require all of a CPU's attention.
TheConfusedOne: Real time usually has to do more with interrupting things in order to meet time constraints (hence the pre-emptive kernel patch). That means that when you program something in real time and say this activity has to happen every five seconds then at that five seconds everything else will be interrupted in order for that activity to occur. (There are of course constraints based on internal timing.) A payroll system has no such constraint. While there are deadlines for people to finish or start activities in the system it doesn't pre-empt any activities.
It's a question of the longest time slice a process can tie up the processor compared to the resolution of the hard real-time constraints. As long as a process can't hang the system, the largest time slice is a function of processor speed. Back in the days of slow hardware, we certainly did pre-empt things to run payroll.
You both seem to be thinking that "real-time" means "fast" when in fact it means that the time constraints are specified with regard to the outside world (thus the phrase "real time"). It doesn't matter if we're talking eons or fempto-secconds, as long as we define success or failure in terms of real world, physical time instead of some internal metric such as processor time.
Of course, the challenge is at the edges, dealing with very small time windows, very long up times, and so forth, and thus these are the things you'll hear people talk about. It's the same in any field. You won't find many cookbooks that devote a chapter to boiling rice, but it's still cooking. And payroll processing is still a real-time application.
-- MarkusQ
Your definition of a real-time system is a little too loose. A payroll system is not a real-time system. Sure, the employees might get angry if the payroll is not submitted on time, but a hard real-time system has well-defined fixed time constraints, and guarantees that these critical tasks will be completed on time. A payroll system makes no guarentees.
I have to side with the original poster. Other than scale, there isn't any difference between a payroll system and something you would typically consider "real time". There are "well-defined fixed time constraints" for payroll processing (in the US often defined by state and federal laws). If you do payroll processing, you guarentee (often contractually) that you will meet the constraints.
In both cases, there are time limits expressed in terms of the outside world("real time"), and sufficient consequences if these constraints are not met to define failure to meet the constraints as system failure. The only difference is scale.
-- MarkusQ
How exactly do you people keep changing from casual to smart clothing every time you need to go visit a client? Does your office have a changing room, or something?
Phone booths.
-- MarkusQ
# gcc communist_manifesto.txt
# diff a.out
#
So what you're saying is that if you compile the communist manifesto you get out a sendmail binary?
No, I think he's (either) suggesting that you compare the result of compiling the file communist_manifesto.txt with the sendmail binary (but not in any way predicting the results) or (under the more likely assumption that the file does not contain a syntactically valid program) pointing out to us 1) that gcc deletes any preexisting a.out if it is given an invalid source file and 2) you can confirm this by trying to diff it with something, since diff will complain that the file doesn't exist.
He's correct, but I can't help but think that there are easier ways of accomplishing the same thing.
-- MarkusQ
P.S. Ah! I see! It's a clever way of removing a.out if and only if the file communist_manifesto.txt exists and does not contain a syntactically valid program. I'm not sure why you would want to do this, but it is a rather clever hack if you need it.
there has been a steady increase in the level of abstraction they use
So, C is more abstract than LISP? And C# is more abstract than Haskell? Or is this "steady increase" just an artifact of how you choose your examples?
Imagine you are hosting a party. The first person to show up will either be taller than you, or shorter. And (if the people are showing up in a random order) there is a non-zero chance that the next person to show up will either be shorter than both of you, or taller than both of you. As new guests continue to arive, we should expect the height of the tallest person present to go up, and the height of the shortest person present to go down.
I would argue that the same thing is happening with programming languages. We are not just seeing higher and higher level languages, we are also seeing lower and lower level languages (e.g. so-called programable hardware, PLAs, etc.) at the low end. More than anything, we are seeing a steady increase in the number of FORTRANistic languages that dwell somewhere between BASIC and C.
But no grand trend in any particular direction.
-- MarkusQ
I like monkeys.
I like monkeys too. Perhaps we should form a school of thought based on them. We could:
If we wanted to really confuse people, we could systematically supress any references to "fish" or "pizza."
I guess my objection to "it's all good" is the same as my objection to games that start off with a screen that says "You've won!" and segue directly to the closing credits. I haven't even had a chance to waste my time. If "it's all good" then none of it is bad, so there's nothing to do. Thanks for playing. What fun is that?
Rationalist/objectivist science is (by contrast) loads of fun. Almost all of the answers are wrong, and you have to really work at it to get a respectible score.
-- MarkusQ
This is the way PostModernism works
PostModernism works? Really? And it has produced...what? I can't off the top of my head think of anything useful that has come out of it, can you? I don't even recall much that was particularly entertaining, at least not enough to justify the whole "movement."
Maybe you meant to say "this is why PostModernism doesn't work."
-- MarkusQ
I am a philosophy student with an intense interest in mathematics and programming...Does anyone...have any recommendations for books dealing with any aspect of programming theory?
It sounds like you are looking for Edsger Dijkstra's A Discipline of Programming, which is great fun if you can juggle math, logic, philosophy, and programming (in a non-deterministic language he made up for the book) without getting fixated on any one to the exclusion of the others. He starts with an interesting angle on why we have computers at all, and builds up from there.
-- MarkusQ
So what prevents a more corrupt administration from...
In theory, something called "checks and ballances." It's a key part of our system; it also prevents things like a rogue president declaring war at random, congressmen passing laws which only help their financial backers, or judges ignoring laws to protect their cronies. Since it's so important, we periodically do a live full system test to make sure it's still working.
In fact, it looks like we're starting one now.
-- MarkusQ
I think you are missing the point. People (yourself included) act as if Bell's inequality ruled out all hidden variable theories--in the sense that it allows us to make testable predictions and the results of testing these predictions are inconsistant with the hidden variable theories. But it only rules out a rather small subset of the possible hidden variable theories and there are many others (such as the extreme case I described) that it does not rule out.
An analogy to show the flaw in the reasoning:
Are they justified in concluding that there is no one in the closet? Obviously not. Does this mean that there is someone in the closet? Again, obviously not. The line of reasoning they are using is not sufficent to answer the general question.IMHO, invoking a universe's worth of hidden state per particle just because you don't like the idea of a random universe isn't much less silly than that.
I don't recall saying that I believed in one model or another, or that I liked or disliked the idea of a random universe, or that it mattered one way or another what I liked or believed. I'm just objecting to saying that a class of theories has been "ruled out" by an argument that only addresses a small subset of the class.
-- MarkusQ
This is almost exactly what I was about to suggest, except that I would use string taped down at the edges (& pulled tight) instead of sticks. Why? It makes it easier to remove the pictures afterwards. You'll probably want to do the following:
Make a point to check that your strings haven't moved every hundred scans or so, and periodically check the cut images as well, just to save yourself from plunging ahead with a miscalibrated setup.
-- MarkusQ
This randomness is distinguishable from so-called "hidden variable" interpretations.
Not quite. There's a hidden flaw in the argument against hidden variables; the "proof" subtily begs the question. To see this, imagine that there were a level of "hidden variables" complex enough that each quanta (quark, lepton, what have you) could have as much "state" as the entire universe as-we-know it. With such a system you could predetermine every "interaction" over the course of the whole history of the universe--there wouldn't be any "physics," just a mind bendingly huge collection of scripted motions.
The point being, there's no way we could detect that this was the case...and thus there's know way we can prove that it isn't the case.
Now, we are free to doubt that we live in such a universe (and believe in "truly random events") but this is just a belief, without any science to back it up.
-- MarkusQ