X & the Book Code - Computerphile
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- čas přidán 10. 01. 2019
- Why some numbers just dont work when you're creating error proof codes. Professor Brailsford continues with the story of ISBN.
/ computerphile
/ computer_phile
This video was filmed and edited by Sean Riley.
Computer Science at the University of Nottingham: bit.ly/nottscomputer
Computerphile is a sister project to Brady Haran's Numberphile. More at www.bradyharan.com
I see Professor Brailsford, I click.
He's one of the people on this channel who can break any concept down into tasty nibbles.
Oh oops forgot to mention : NOW send him to IBM to ask them snarky questions about their new Quantum Computer.
It's such a pleasure to watch the professor. Brilliance, passion, and a gift for explaining.
8:32 ”If you want to divide by n, it's the same as multiplying by 1/n."
_Prof. Brailsford, 2019_
Yep cray supercomputers used that instead of a divide instruction. Was apparently much easier to pipeline
@@tomcombe4813 Makes sense, you can have a chip that's specially designed to calculate inverses (1/n) instead of a full division circuit. I'm sure there's some tricks to make that work a lot faster than a full division chip would then you can just multiply which is something you'll need to be able to do anyway.
@@grn1yeah. I think it's something to do with the operation only having one variable.
Also a lot of chips have single cycle multiply now so converting division to multiplication really speeds things up
Can you ask the professors about design patterns. I'd like to hear a video where they talk about the gang of four and the history of design patterns
Does this mean a sequel on Galois fields? I’ve been hoping for a computerphile video on Galois fields since I first tried to wrap my mind around AES
Yes, I'll hope to be doing just enough on Galois Fields (but only of type 2^n) to show the principles of field polynomials etc in a very simple Reed-Solomon example.
ProfDaveB - Can't wait! You break things down so well and make it easy to understand complex topics like this.
me feel big brain watching smart number video
yous has a oopsie. it watch* no watching,
Looking forward to the next video!
I love all the people that are in these videos, but I have a special love for Professor Brailsford.
For those wondering the significance of 0 for addition and 1 for multiplication (those unfamiliar with abstract algebra) the reason is that 0 is the "identity element" for addition, and 1 is the identtiy element for multiplication ie 0 + anything = anything, and 1 x anything = anything.
This can (and is) generalized to other operations as well and the same ideas apply.
It's been 5 years since a Computerphile video on "extra bit" logic (ternary etc.)
I think with the recent attention to IBM's new quantum computer this would make a quite popular, and important video.
Professor Brailsford. Such a lovely chap. :-)
I only kinda vaguely grasp the nuances of this, but it's interesting nonetheless. And Prof. Brailsford delivers it so compellingly. Amazing presenter.
ISBN-10 uses descending weighting in the real world, so the check digit usually only has a weight of 1, whereas the first digit will have a weight of 10.
Interesting! The end result is the same either way, but I didn't know that before your comment prompted me to look it up. There may be some programmers who accidentally implemented the algorithm 'backwards' and never found out about this symmetry because all tests check out anyways.
That end smells very distinctively of polynomial division.
1:24 Will I be able to overcome the challenge? I hope so, but turns out if you just put the first nine digits into a search engine, you get the answer immediately. Now on to watching the rest of the video ...
Absolutely fun challenge, thank you. M.
1:22 Quantum Chill aka. Young Galois, I miss you
You did an episode on Unix, could you do one about BSD? That would be really nice.
First. I apologize.
This is actually the only time I’ve been first on a video and I find it quite poetically beautiful that it has happened on a video that specifically requests that you abstain from “firsting”.
You're actually first :O
Gonza2323 Yessir/yessum.
Since you find it so difficult to resist your oppositional urges, I guess it's fortunate they didn't request that you abstain from "fisting".
MegaFonebone fair enough.
You point to 0 as the "additive inverse" and 1 as the "multiplicative inverse" when they're actually called the "additive identity" and "multiplicative identity"
Laurie O but they're here used to find the inverse. With multiplication, 1 is the identity because anything multiplied by 1 should equal itself. However what we're interested in is what we can multiply a number by to give 1, i.e. a*b=1. In this case b is the multiplicative inverse of a, and we can find the inverses easily by searching for the '1's in the table. Same for addition; 0 is the identity because anything plus 0 is itself, but we want a+b=0 (mod whatever the base is)
You're right: that was clarified at 14:53. I was pointing out a mislabelling
The x windowing system would be a cool video topic
Hello Professor, can you make a video on how low latency applications work - for eg Trading Applications ? What is the skill set required for developing such applications ?
i am lost. i am not a native speaker and i seem to have lost sth there. what is the subject of the video?
At 18:10 -- you have to be able to find a '1' on every single row of the table *except* the 0 row. That one gets to be special.
This is fantastic!
I can tell due to the format of the ISBN having a large registrant element that it must be from a large publisher.
Hit or miss, I guess they never miss 1:23
Did the next video in this series ever get made?
Hey I understand some of these words!
Apparently he is also a gangster in LA.
Little Feat are an awesome band!
computerphile meets group theory! numberphile will be twitching!
I was thinking "What does the windowing server have to do with two people having the same book and sending secret messages to each other?"
The AWK Programming Language
Terse
Explain, please.
@@MegaFonebone That's the book the ISBN example comes from.
@@BrightBlueJim Ahhhh, thanks. I was racking my brain trying to figure out how AWK was related to this topic.
I figured it'd be K&R C but hey, awk is cool too
How hilarious would it have been if the book he'd chosen as the answer was either Faust or something by Furst.
I feel like I walked into a lecture late by about 15 minutes. I guess my primary mis-assumption was that "book code" referred to encryption, and hearing about weighted checksums and the mention of prime numbers did nothing to dispel this. But since he was going on and on about ISBN numbers, then I thought maybe this was a way of including the key (i.e., a coded representation of the book on which the code is based) in the coded message, leading me further astray. By the time I realized what this was about, I had lost all interest!
Remainders - another root from the literary tradition?
Says 3 holds up 4 fingers
Algebra
📺💬 Modulation and calculation of the ISBN mode for verification and categorization.
🥺💬 We also have experience with modulo verification such as Thai citizen ID number, Passport, and many applications that are using the same method or enchant with alphanumeric where it can verify the series without source access but with source access, it quickly searches for the categories or properties.
🧸💬 Can you give more examples off the edges of security information anyway car plates or other registration are running numbers and random selection and modulation we also use it with caseID and information ID generated or haze it as a string?
🐑💬 I want to see the error correction using modulation, we had learned about multi-phase signals, and the error correction combined with the signaling property creates something like hamming radios that resistance to radios interferes.
🥺💬 Everything starts from a small but see now today what applied the modulo agilities⁉
📺💬 Adjective inverse 2 behaves like 3 - 1 when the modulo of 3 becomes 0 the result is [ 1, 2, 0 ] or it is remainder to the N - 1.
🐑💬 It creates factorials or identical when modulo with prime number and we can keep the set of prime numbers in a secret chamber only the source can read from its messages.
🥺💬 In programming, we do not modulo of input to create another input but the inverse modulo is a fast calculation compared to multiple-time multiplication for reading a message.
🦭💬 Working functions we called modules because frequent output and sensors are modulated by the modulator and somebody thinks the meaning comes from replaceable but it is not.
You hurt my head
The AWK Programming Language... but you do realize we have google, right?
I always wonder what would be the reason to dislike this video?
4:49
NOT FIRST!
i wish i have half this mans knowledge I'll be a millionaire in no time
6204th MOD 1
prawn = u-dang
Brailsford
31267st!
AWK? :P
0 x 0 = 1
i would have just solved 10c as 10c = -c = 1 = -10, c=10, generally this halves the amount of work you need to do.
First my friendo
Blehhhhhhhh, this hurts me in the abstract algebra :'(
FIRST
10:18 >"by doing a multiply and and addition table for 3"
>holds up four fingers
I see Prof. Brailsford uses an index-0 numbering system.
First!
First! *races off*
First (modulo 11)
Missed opportunity to write 12th (mod 11).
first
First!
Sorry.
Zeroth! :D
Zeroth
First. Almost
!=first
First
ISBN 020107981x The AWK Programming Language by Kernighan et al....
The AWK Programming Language
First!
first
The AWK Programming Language
The AWK Programming Language
The AWK Programming Language
first