(-_-)(0-0)(o_O)

Zangeef: Deto 3aref ya3nee eeh erasure coding?
Me: Nope eeh dah?
Zangeef: ana 3aref ? aho bta3 keda 3ayzeeno taba3 el RFP el gdeed!
Me: bta3 el recovery?
Zangeef: ah, matshofo m3aya keda ya abo el mahadeet
Me: shoor! el7a2ni el7a2ni yabn el genniiiiii!! *Googles erasure coding*
Me: khod … ekhbat de: http://en.wikipedia.org/wiki/Erasure_code [tty 3m]
Zangeef: ack
Me: slide

excerpt from the wiki page bear with me -DO NOT SKIP-

Alice wants to send her telephone number (555629) to Bob using err-mail. Err-mail works just like e-mail, except
1.About half of all the mail gets lost.[1]
2.Messages longer than 5 characters are illegal.
3.It is very expensive (similar to air-mail).
Instead of asking Bob to acknowledge the messages she sends, Alice devises the following scheme.
She breaks her telephone number up into two parts a=555, b=629, and sends 2 messages – “A=555″ and “B=629″ – to Bob.
She constructs a linear function, f(n) = a + (b − a)(n − 1), in this case f(n) = 555 + 74(n − 1).

She computes the values f(3), f(4), and f(5), and then transmits three redundant messages: “C=703″, “D=777″ and “E=851″.
Bob knows that the form of f(n) is f(n) = a + (b − a)(n − 1), where a and b are the two parts of the telephone number. Now suppose Bob receives “D=777″ and “E=851″.

Bob can reconstruct Alice’s phone number by computing the values of a and b from the values (f(4) and f(5)) he has received. Bob can perform this procedure using any two err-mails, so the erasure code in this example has a rate of 40%.
Note that Alice cannot encode her telephone number in just one err-mail, because it contains six characters, and the maximum length of one err-mail message is five characters. If she sent her phone number in pieces, asking Bob to acknowledge receipt of each piece, at least four messages would have to be sent anyway (two from Alice, and two acknowledgments from Bob). So the erasure code in this example, which requires five messages, is quite economical.

Zangeef: ha gamma3t eeh?
Me: Bob is one lucky bastard !
Zangeef: Word.

~ by mahdeto on May 10, 2009.