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On 9/30/2011 1:18 AM, Invisible wrote:
> On 30/09/2011 03:14 AM, Patrick Elliott wrote:
>
>> Depending on your definition of "computer"
>
> There is that too.
>
> Turing-completeness is a reasonable definition, until you consider that
> a sheet of paper and a pen is Turing-complete given a suitable human to
> operate it. So perhaps the significant thing is the sophistication of
> computations that the device can perform without human aid.
>
>> there is evidence of a one
>> of a kind "Roman" device that was capable of predicting eclipses, and
>> timing the correct date to start the Olympic games, among other
>> features.
>
> Last I heard, nobody had decided exactly what that device was for. It
> seems opinions have changed...
>
>> In other words, an electronic calender.
>
> I think you mean /automated/ calendar. It's only /electronic/ if it
> operates by moving electrons around. :-P
>
Uh, yeah.. lol
>> But, at that time,
>> such things where nearly impossible to replicate, so when the ship it
>> was one sank...
>
> We're talking about something from a /long/ time ago. The fact that no
> others have been found yet doesn't mean none existed.
>
This is true, but from a purely practical standpoint, the expense,
precision, and engineering needed to get just "one" to work, using
basically copper and bronze gears, and little if any fast and replicable
casting methods (where talking hand making each gear here), the odds of
an exact copy is pretty much nil. The odds of something similar, still
close to zero. Something much simpler.. possibly, but its basically a
clock, more or less, and I am pretty sure that water clocks where just
about as close as they ever got, based on everything known/found/written
about, other than this thing, to that level of precision. Even some
mechanisms they used in temples, to open and close doors, where "one
off" designs, which where never exactly replicated, and are only half
known, half speculated, at this point (given the missing bits, and
descriptions we have to go off of).
If you wanted something that could use water to time things to the hour,
or measure an exact amount of "holy water" to do something with in a
temple, you where in good shape, since the mechanisms didn't need to be
*that* precise. Something like a mechanical calender... Hope you own
stock in the Colosseum. lol
>> Arguably, its gearing system had to have some sort of "algorithm".
>
> By that description, the way that trees use the laws of physics to move
> exactly the right amount of water from their roots to their leaves could
> be considered an "algorithm". Which would mean that algorithms predate
> mankind by several billion years...
Umm, well.. I would argue that what makes it an algorithm is the
"intentional" development of the steps and process needed to form a
predictable result. Gearing matches this definition. Stuff that just
kind of does that already, naturally... is a bit iffier. But, that isn't
to say that, say genetics, couldn't contain something that could be
"interpreted", if you had the right JIT compiler, so could be, to an
extent, algorithmic. Water happening to get from roots to leaves.. not
so much.
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On 9/30/2011 8:47 AM, Stephen wrote:
>> Regardless, have you ever actually seen an analogue computer with
>> independently addressable memory cells? I haven't heard of such a thing.
>>
> What to answer first? I don't know, the only actual working valve
> computer I've ever been in the presence of was at Glasgow University,
> over 40 years ago. I've never had hands on experience working with them.
> But you would not use addressable memory as you would in digital
> computers. Remember that we are talking about voltage levels
> representing numbers. Also back in the day, what was being asked of then
> was much simpler and less complex so a lot of memory would not have been
> required.
>
Just use a large, covered, lake as the "storage". You get a certain
level of error, and possible leaks, but you could compute a number as
large as... what ever the lake could contain in what ever unit of water
your system dealt with. lol Seriously though, I would say that the
distinction between digital and analog in this sense is a) how long you
can hold the value, and that assumption that the value you can hold has
a set number of limits, in DNA, assuming you where using it to encode
numbers, that is like what 4 values (ATGC), in some indefinite set of
combinations, 3 states, for like the "quantum" systems they are trying
to develop, or 2, on/off, for current systems. In all of these cases,
the "values" are discrete, hence digital. You can't, in the case of
something like DNA "get" any other values (unless you just completely
change the proteins involved), I am not sure what you get with quantum
effects, but generally they seem to be discrete states, but with binary
we *intentionally* ignore any difference of state, other than below X
level, or above it. So, if your "analog" circuit had these values 0.1,
0.3, 0.6, 0.12, and 0.7, "binary" simply enforces the rule that this is
actually 00101.
In principle, your "analog" computer just throws out that assumption.
The result is less reliable, which is the main reason we stopped trying
to use it. But, in theory, if someone had wanted to, they maybe could
have made a base 10 computer, by treating each "range", 0-0.1, 0.11-0.2,
etc. as a different "state". It probably wouldn't have been at all
feasible, in that the fail rate on circuits that didn't produce the
correct result, or match specifications, would have been much, much,
larger. Like, if now we threw out one in every 1,000 processors, you
might see a fail rate of like 1:50 for such a base 10 system, or worse.
Because, of you are dealing with on and off, 0.6-1.0 is "acceptable" for
the "on" state, and 0-0.4 might be for the "off", with only the absolute
middle range of values being too ambiguous.
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> On 9/30/2011 8:47 AM, Stephen wrote:
>>> Regardless, have you ever actually seen an analogue computer with
>>> independently addressable memory cells? I haven't heard of such a thing.
>>>
>> What to answer first? I don't know, the only actual working valve
>> computer I've ever been in the presence of was at Glasgow University,
>> over 40 years ago. I've never had hands on experience working with them.
>> But you would not use addressable memory as you would in digital
>> computers. Remember that we are talking about voltage levels
>> representing numbers. Also back in the day, what was being asked of then
>> was much simpler and less complex so a lot of memory would not have been
>> required.
>>
> Just use a large, covered, lake as the "storage". You get a certain
> level of error, and possible leaks, but you could compute a number as
> large as... what ever the lake could contain in what ever unit of water
> your system dealt with. lol Seriously though, I would say that the
> distinction between digital and analog in this sense is a) how long you
> can hold the value, and that assumption that the value you can hold has
> a set number of limits, in DNA, assuming you where using it to encode
> numbers, that is like what 4 values (ATGC), in some indefinite set of
> combinations, 3 states, for like the "quantum" systems they are trying
> to develop, or 2, on/off, for current systems. In all of these cases,
> the "values" are discrete, hence digital. You can't, in the case of
> something like DNA "get" any other values (unless you just completely
> change the proteins involved), I am not sure what you get with quantum
> effects, but generally they seem to be discrete states, but with binary
> we *intentionally* ignore any difference of state, other than below X
> level, or above it. So, if your "analog" circuit had these values 0.1,
> 0.3, 0.6, 0.12, and 0.7, "binary" simply enforces the rule that this is
> actually 00101.
>
> In principle, your "analog" computer just throws out that assumption.
> The result is less reliable, which is the main reason we stopped trying
> to use it. But, in theory, if someone had wanted to, they maybe could
> have made a base 10 computer, by treating each "range", 0-0.1, 0.11-0.2,
> etc. as a different "state". It probably wouldn't have been at all
> feasible, in that the fail rate on circuits that didn't produce the
> correct result, or match specifications, would have been much, much,
> larger. Like, if now we threw out one in every 1,000 processors, you
> might see a fail rate of like 1:50 for such a base 10 system, or worse.
> Because, of you are dealing with on and off, 0.6-1.0 is "acceptable" for
> the "on" state, and 0-0.4 might be for the "off", with only the absolute
> middle range of values being too ambiguous.
>
There is another consideration: Power consumption and heat dicipation.
With a binary gate, you consume almost no power on a zero or a one. You
do consume a lot more when you switch value and are at an intermediate
state.
With a decimal processor using 10 ranges, 8 times out of 10, you are at
a steady intermediate state that forces you to dicipate much more heat.
Things get even worst if you want to create an analog logic switch.
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>>> But, at that time,
>>> such things where nearly impossible to replicate, so when the ship it
>>> was one sank...
>>
>> We're talking about something from a /long/ time ago. The fact that no
>> others have been found yet doesn't mean none existed.
>>
> This is true, but from a purely practical standpoint, the expense,
> precision, and engineering needed to get just "one" to work, using
> basically copper and bronze gears, and little if any fast and replicable
> casting methods (where talking hand making each gear here), the odds of
> an exact copy is pretty much nil. The odds of something similar, still
> close to zero. Something much simpler.. possibly, but its basically a
> clock, more or less, and I am pretty sure that water clocks where just
> about as close as they ever got, based on everything known/found/written
> about, other than this thing, to that level of precision.
That's interesting, because Wikipedia claims there's a long documented
history of ideas similar to this one, starting with Archimedes...
>>> Arguably, its gearing system had to have some sort of "algorithm".
>>
>> By that description, the way that trees use the laws of physics to move
>> exactly the right amount of water from their roots to their leaves could
>> be considered an "algorithm". Which would mean that algorithms predate
>> mankind by several billion years...
> Umm, well.. I would argue that what makes it an algorithm is the
> "intentional" development of the steps and process needed to form a
> predictable result.
Indeed.
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On 30/09/2011 07:32 PM, Darren New wrote:
> On 9/30/2011 10:04, Orchid XP v8 wrote:
>> Small difference: ALUs require energy. A storage medium typically
>> doesn't.
>
> ALUs don't require much energy. Look up "reversible computing" some
> time. That's what it's all about. And yes, people have actually built
> computers that take no energy to run, using quantum effects.
I thought the problem with reversible computing is that it's just as
likely to run backwards (which is no use at all) as to run forwards?
>> If you're saying "you could make an analogue computer that was
>> Turing-complete" then, yes, of course you could. If you're saying "the
>> analogue computers what people actually built were Turing-complete" then,
>> no, not really...
>
> Well, sure, and neither are the real digital ones. That's kind of my point.
By that definition, nothing that can exist in the physical universe will
ever by Turing-complete. That's not a useful definition.
>> Exhibit A: Totallistic cellular automaton number #110.
>
> Exactly.
You said "it's always absurdly easy to prove that something is
Turing-complete". I hold up an example of something that took ages to
prove, and even now some people argue the proof isn't very sound.
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On 10/3/2011 1:03, Invisible wrote:
> I thought the problem with reversible computing is that it's just as likely
> to run backwards (which is no use at all) as to run forwards?
Yes. Basically, it takes as much energy as you need to keep it moving
forward. The less energy you give it, the slower it goes. If you give it no
energy, it stops (on average) making forward progress.
OK, it doesn't take *no* energy. It takes arbitrarily little energy.
> By that definition, nothing that can exist in the physical universe will
> ever by Turing-complete. That's not a useful definition.
Yes it is, if what you're talking about is what's possible to even
theoretically calculate.
> You said "it's always absurdly easy to prove that something is
> Turing-complete".
No I didn't. I said it's "usually not too hard."
> I hold up an example of something that took ages to prove,
> and even now some people argue the proof isn't very sound.
Sure. But that's because he's pushing the boundary. He's not interested in
whether a CA can be Turing complete. He's interested in the absolute
simplest CA that can be proven to be Turing complete. I'd argue that that's
intentionally on the very boundary of what's most difficult to prove, rather
than the "usually" case.
--
Darren New, San Diego CA, USA (PST)
How come I never get only one kudo?
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On 10/3/2011 1:01 AM, Invisible wrote:
>>>> But, at that time,
>>>> such things where nearly impossible to replicate, so when the ship it
>>>> was one sank...
>>>
>>> We're talking about something from a /long/ time ago. The fact that no
>>> others have been found yet doesn't mean none existed.
>>>
>> This is true, but from a purely practical standpoint, the expense,
>> precision, and engineering needed to get just "one" to work, using
>> basically copper and bronze gears, and little if any fast and replicable
>> casting methods (where talking hand making each gear here), the odds of
>> an exact copy is pretty much nil. The odds of something similar, still
>> close to zero. Something much simpler.. possibly, but its basically a
>> clock, more or less, and I am pretty sure that water clocks where just
>> about as close as they ever got, based on everything known/found/written
>> about, other than this thing, to that level of precision.
>
> That's interesting, because Wikipedia claims there's a long documented
> history of ideas similar to this one, starting with Archimedes...
>
Not always evidence they where actually built though. And, again, its a
matter of "size" and "complexity". Heck, even Babbage ran into the issue
of, "I think this will work, but there is no way in hell I could ever
build this thing."
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>> That's interesting, because Wikipedia claims there's a long documented
>> history of ideas similar to this one, starting with Archimedes...
>>
> Not always evidence they where actually built though.
There seems to be plenty of documentation of people who claim to have
seen these devices in operation.
> And, again, its a
> matter of "size" and "complexity". Heck, even Babbage ran into the issue
> of, "I think this will work, but there is no way in hell I could ever
> build this thing."
No, that wasn't the problem. Babbage's problem was that he kept
tinkering with the design. Always thinking up new ways to improve it.
Eventually the workmen got hacked off with trying to build a design that
changes every five minutes. Plus, I gather Babbage was not a patient
man, and rather awkward to work with.
In a way, he seems to have been like me: Full of good ideas, but an
incurable tinkerer, and never actually finished anything...
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On 10/4/2011 1:08 AM, Invisible wrote:
>> And, again, its a
>> matter of "size" and "complexity". Heck, even Babbage ran into the issue
>> of, "I think this will work, but there is no way in hell I could ever
>> build this thing."
>
> No, that wasn't the problem. Babbage's problem was that he kept
> tinkering with the design. Always thinking up new ways to improve it.
> Eventually the workmen got hacked off with trying to build a design that
> changes every five minutes. Plus, I gather Babbage was not a patient
> man, and rather awkward to work with.
>
> In a way, he seems to have been like me: Full of good ideas, but an
> incurable tinkerer, and never actually finished anything...
Sounds like the guy that worked for Twain, when he was trying to help
fund a printing press. The "simpler" model won out, despite the fact
that the one they where funding could do vastly more. The guy making it
kept taking it apart, to "improve" the thing, instead of ending up with
a fully working model.
Still, its been argued that it would have been problematic mass
producing the thing, at the time, too. Or, at least I read that some place.
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>> In a way, he seems to have been like me: Full of good ideas, but an
>> incurable tinkerer, and never actually finished anything...
> Sounds like the guy that worked for Twain, when he was trying to help
> fund a printing press. The "simpler" model won out, despite the fact
> that the one they where funding could do vastly more. The guy making it
> kept taking it apart, to "improve" the thing, instead of ending up with
> a fully working model.
Why Projects Are Delivered Late And Over Budget. Robertson et al.
...or not. ;-)
> Still, its been argued that it would have been problematic mass
> producing the thing, at the time, too. Or, at least I read that some place.
Depending which "thing" you refer to...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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