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  • >> Sean: Professor Brailsford - a lot of people talk about von Neumann architecture and

  • we've talked about Babbage; we've talked about Turing. Who was von Neumann ?!

  • >> DFB: We've done a lot about Turing; we've done a fair bit about Babbage, in the

  • generation earlier. In fact a lot of people, I guess, in the English-speaking

  • world would regard Turing, in some way, as being the Father of Computing. He came up

  • with this very important result, in the mid-thirties, about what was computable,

  • and as we now know. to his credit. he wasn't at all afraid to burn himself with a

  • soldering iron and try to create hardware. Which he did at Bletchley Park

  • during the war. So, yes, if he's the Father, if Babbage was the Grandfather and if Ada,

  • Countess of Lovelace, was the Great-Aunt,

  • then who on earth was John von Neumann? And why is he mentioned alongside Turing?

  • Well right at the outset let's say John von Neumann was the impossibly talented,

  • impossibly charismatic, very wealthy, Uncle to computing. It was he that, in the

  • mid-1940s, in a way, made it all happen by the force of his own personality. And

  • kept it, not just in an enclosed community, but encouraged all those who

  • wanted to build general-purpose computers to come along to this Summer

  • School and do it. But that really, I guess, is in the future. It's where we've got to

  • get to in the von Neumann story. But, yes, you're quite right Sean, to say that one

  • of the first phrases that almost any computer scientist hears about is The

  • von Neumann Architecture for computers, which to a large extent we still follow

  • even now - all of, what 60-70 years later. So, we've mentioned EDSAC before, we'll

  • be coming back to mention this very important early computer again. But it is

  • a von Neumann machine and all it's saying is [that] it's very simple to build a

  • computer. You need a Store, or Memory as it's more commonly called nowadays, to

  • hold your instructions and your data. You need a

  • control unit, often called a CPU now. And you need an arithmetic capability - the

  • ALU, the arithmetic and logic unit. Again many of you will know in modern chips

  • those two are often combined into what we just call "the CPU chip" nowadays.

  • And you need input devices of various sorts leading back to people's Teletypes [with]

  • input/output devices for backup storage, disk and so on. You need to be able to do

  • input and output. So there it is. It's just one, two, three, four, five boxes - that

  • is the von Neumann architecture. And it's very, very similar today. There was a big

  • debate at the time about that Store that Memory. Shouldn't you, for safety's sake,

  • put the instructions of your program in a different sort of memory to your data?

  • Wouldn't it be safer to do that and better in some ways? On the other hand,

  • clearly, if you've got a good memory technology, that works, the temptation

  • might be just to put them [instructions and data] in separate areas of that same technology and try

  • and take some sort of precaution about them not interfering with each other. In

  • EDSAC the only way to get into a subroutine and get back out of it again

  • was to over-write part of your program instructions! Let's just return back to

  • this incredible character John von Neumann. How does he fit in alongside

  • Alan Turing? Well, like I said, he's the older, impossibly talented, Uncle. Did

  • Turing and von Neumann know each other? Oh yes they did! They were both, basically,

  • trained as mathematicians. Von Neumann - it's hard to know where to begin and

  • where to end. You can't exaggerate enough about how

  • good he was. He was Hungarian and his Hungarian name - where they give surnames

  • first - was, I think, Neumann Janos. His father was very, very wealthy and

  • when one was quite young the family became ennobled in Hungary. [They] became

  • basically at the level of Baron - hereditary Baron I think

  • over here. Janos was very talented; he was a childhood prodigy. He could divide one

  • eight-digit number by another eight digit-number in a fraction of a second

  • when he was aged about 6. He loved history; he was a multi-talented polymath

  • he easily came top of the class he effortlessly took in detail. And that's

  • the first thing that all of his mathematics contemporaries said about

  • him was his sheer speed of picking up new ideas and seeing the ramifications

  • of them. So he was notorious even as a teenager, and as a maths undergrad. He did

  • his early education I think up to PhD level in Budapest. He almost naturally

  • ended up at a place we mentioned before in connection with Godel and Hilbert.

  • I'm talking, of course, about Gottingen University in Germany. So Neumann Janos

  • makes the journey, via a PhD, to becoming effectively the research assistant

  • to the superstar David Hilbert at Gottingen. But because his family

  • had been ennobled he's not Janos Neumann any more - Neumann

  • Janos sorry - he's Johann von Neumann - impossibly talented. Hilbert his

  • supervisor, at a seminar given by Johnny,

  • John, Johann (!) asked who his tailor was. Because his impossibly smart

  • pinstripe suit was just a complete knockout. So he was a legend almost the

  • moment he got there and did some fabulously important work there. It was

  • obvious that for somebody of his talents he was going to get a full Professorship

  • very quickly indeed. I think he became impatient, waiting for it to happen at

  • any German university. So, in the late thirties - '37-'38? Somewhere around there anyway -

  • Anyway he got an offer from Princeton, in New Jersey. And that was, I don't know,

  • very timely. It all fitted in together very well. As part of his tours of Europe,

  • giving seminars, and on his way to Princeton, I think he met Turing in the

  • mid-thirties in Cambridge. Because he gave seminars there

  • and I think a lot of mutual respect grew up. I mean, obviously, Turing being in awe of

  • von Neumann wouldn't be so exceptional. But after that 1936 paper of Turing's,

  • about decidability, following on from Godel and all that, von Neumann rated

  • Turing - there was no question about that. This was evidenced by the fact, you will

  • recall - those of you who have seen my previous videos - that Turing also took a

  • sabbatical and worked with Alonzo Church at Princeton.

  • Well, von Neumann was there by that time. Von Neumann was such a superstar, they not only

  • made him [full] Professor of Mathematics at Princeton, at an absurdly early age -

  • probably about 30, something like that. But some of you will recall, right next

  • door to Princeton - about a mile and a half across the meadows - is the Institute

  • for Advanced Study which had been endowed in the early 1930s by a

  • multi-millionaire. And this really was the ultimate Club to be invited to join.

  • You've got to be of the quality of Einstein, who accepted the invitation.

  • Hermann Weyl one of the founders of quantum mechanics; Godel - we know about

  • Godel. Godel was invited to just come to IAS - Institute for Advanced Study at

  • Princeton - stay as long as you like. Yes, you're a Professor; everything found: food

  • accommodation; the lot. All we want is to have the greatest minds here. Von Neumann

  • was offered a professorship in that community, I think at age 35 - maybe

  • slightly younger. Unbelievably young. He'd hardly been at Princeton a year or two, as

  • an ordinary mathematics professor. Everybody thought "This is a truly

  • phenomenal person". He reminded many people of absolute superstars like

  • Newton, Gauss, Euler, Einstein, Hilbert himself. Even at early to mid-

  • thirties they could see that potential in him, there. So, yes, Turing visits

  • Princeton in 1938 - worked with Alonzo Church - but also of course had frequent

  • interactions at seminars with von Neumann And then came the big question,

  • if you recall, for Alan Turing: "Should I return to England and do my patriotic

  • duty?" According to Andrew Hodges' definitive biography of Turing,

  • Turing's father was all for Turing staying in Princeton, you know: "Keep out

  • of the war; get a prestigious mathematics job". And that was underlined by the fact

  • that von Neumann offered Turing a job. He basically said: "Turing, would you like to

  • be my research assistant at the Institute for Advanced Study?" Now

  • Turing could see, straight away, that would just make you as a mathematician.

  • You were invited, by the great von Neumann, to be his research assistant, at IAS!

  • Only problem was, I think, first of all, I think Alan Turing did feel a certain

  • patriotism in wanting to come home and do his bit. There was also the worry that

  • at that time von Neumann had not properly got into computing - he'd not

  • turned his considerable talents to considering it - and for the research

  • assistantship he wanted Alan Turing to do quantum mechanics, another of von

  • Neumann's great loves. And I don't think Turing was keen on that because he

  • knew from experience, at Cambridge, where he'd tried doing mathematical physics, it

  • really wasn't his arena at all. So he politely declined with great thanks, came

  • back to England and the rest, if you like, is more or less history. Now there's

  • "Johnny", as he'd now become. Johann von Neumann speaker of four, five languages

  • including Italian and English, once he'd transferred from Gottingen to Princeton,

  • wanted to become the all-American genius. So he was ... on more formal occasions he

  • was just John von Neumann but to his friends he was "Johnny". You can't

  • exaggerate enough! I mean, his wife said: "He can count everything but calories". He was

  • fond of food and drink; the champagne parties! the glitz! the glamour! the

  • girlfriends! Good old Johnny - he absolutely was the antithesis of the

  • shy mathematician. He was all- encompassing and everybody who met him

  • was just stunned by how he could see his way through

  • problems in no time flat. And just do impossible things. And so he was there, in

  • a very ,very nice position, Institute for Advanced Study, even before the

  • Americans joined the war. But he stayed there throughout the war. But being who

  • he was he was endlessly in demand to be a consultant and, most famously, along

  • with people like J Robert Oppenheimer he was one of the consultants employed on

  • the Manhattan Project - the atomic bomb and the hydrogen bomb. But he was used by the

  • Army, the US Navy, the Air Force - everybody wanted Johnny as their

  • consultant. And this even included, as the war developed, the fact that one of the

  • earliest computers which we have mentioned in a previous video was

  • University of Pennsylvania, Moore School of Engineering. They helped develop the

  • ENIAC which, if you remember, was a vacuum tube computer running on decimal

  • arithmetic and initially devoted to gunnery trajectory calculations. It was a

  • bit late in 1946 to be in direct strategic use in gunnery, Actually Johnny,

  • who by this time *of course* was a consultant to the Moore School, devised a

  • way, I think, to turn ENIAC into being a general purpose computer, although it

  • wasn't a very efficient one, and I believe he used it for some calculations

  • relevant to the atomic bomb and all that kind of thing. The natural question

  • arising with everybody at the end of the war went like this: "We all know - or even

  • though it's top-secret at Bletchley Park we have heard gentle rumours - that

  • computers are being developed all over the place and you've always got to say:

  • Are they special-purpose? Are they general-purpose? Are they

  • binary? Are they decimal? Are they fully electronic? Or are they electromechanical?

  • And literally there must have been at least a dozen machines around that

  • satisfied some of these criteria. If you ask Germans about "Who's the father of

  • computing?", they'll say "Konrad Zuse", He developed electromechanical

  • machines that were Turing-complete and calculated things. But they never got

  • beyond electromechanical. You get on to electronic ones - you get Atanasoff

  • and Berry's electronic, valve driven, thing - special purpose though! Could solve

  • certain differential equations. And even Tommy Flowers, and Colossus, we know,

  • special purpose: could decrypt Tunny traffic - Lorenz cipher as it later become

  • known as. So, you've got everything happening that if it's general-purpose

  • it's not yet electronic; if it's special-purpose it is electronic but we

  • want it to be general-purpose. So, at the end of the war was the perfect time to

  • get everybody together and say: "Look, now that the war's over we all want to find

  • the way to do it correctly. To build general-purpose, probably binary-based

  • because they're more reliable, all electronic digital computers. How do we

  • do it"? And who better to lead the charge and

  • run a Summer School, and be associated with it, than uncle Johnny of course!

  • And the Moore School at Pennsylvania, to their great credit, did this. They decided that

  • the successor to ENIAC would be a thing called EDVAC. They said, yeah, it's

  • going to take us three or four years to do this but in the meantime here we are,

  • 1946, why not all of you, all over the world, who are interested in the quest to

  • build general-purpose, all electronic, digital computers, probably based on the

  • binary system ... we'll hold a Summer School in the Moore School of Engineering, 1946,

  • welcome everybody. Did Turing go to it? He was, I believe, at that time at the

  • National Physical Laboratory in the UK No he didn't.

  • Hated conferences did Turing. He wasn't a clubbable character. He couldn't stand

  • small-talk. Classic shy mathematician not at all like

  • von Neumann, right? So Turing wasn't, if you like, the UK representative there. And one

  • wonders whether he would also been held back by Bletchley Park and the Official

  • Secrets Act because he'd only just left a few years before. The representative from

  • the UK was somebody who was Turing's exact contemporary. They had both done

  • mathematics in the early 1930s, at Cambridge. They had both got first-class

  • degrees. Did they get on? Not very well! But who's this other person? His name is

  • Maurice Wilkes - Maurice Vincent Wilkes - and by the vagaries of job allocations

  • around about World War II, he didn't end up at Bletchley Park, did Maurice, he ended

  • up in radar. But he knew enough about mathematics and electronics to be in a

  • good position to do, or make, a von Neumann machine in the UK in the period

  • from about 1946 onwards. But we'd better stop there because Maurice and his EDSAC

  • is an extra story.

>> Sean: Professor Brailsford - a lot of people talk about von Neumann architecture and

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フォン・ノイマン・アーキテクチャー - コンピュータマニア (Von Neumann Architecture - Computerphile)

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    林宜悉 に公開 2021 年 01 月 14 日
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