Re: Ddo ca'c loa.i tre^n ddo+`i.

[Hong Lam Vu <vuh000@goofy.zdv.Uni-Mainz.de>]

Hi ba'c Vie^.t,

>   Tro+? la.i ddo ba(`ng chi? entropy tho^ithi` entropy cu?a tie^?u 
> thuye^'t VN ba(`ng so^' byte trong Hoa`ng Le^n Nha^'t tho^'ng chi' sau 
> khi la^'y log. Anh thu+? ddem so vo+'i va(n ho.c kha'c cu`ng tho+`i thi` 
> tha^'y hay dda'o dde^?.

Hay o+? cho^~ na`o? ne^'u chi? dde^'m so^' byte ru`i la^'y log thi` cha'n
qu'a. 

Tro+? la.i ca'i co^ng thu+'c cu?a ba'c NDNgo.c:

Tri thu+'c = Kho^'i luo+.ng kie^'n thu+'c x (to^'c do^. mo^ pho?ng)^2

ma` 
Kie^'n thu+'c = kho^'i luo+.ng tho^ng tin x (to^'c do^. xu+? ly') ^2

ba'c Ngo.c cu~ng ddo^`ng y' kho^'i luo+.nmg tho^ng tin ddo ba(`ng bit,
to^'c do1. xu+? ly' tho^ng tin nhu+ va^.y la` bit/s, ta.m cho Kie^'n
thu+'c chi'nh la` Kho^'i luo+.ng kie^'n thu+'c thi` co`n du+ la.i va^'n
dde^`: to^'c ddo^. mo^ pho?ng ti'nh ba(`ng gi`. Tui nghi~ kho^ng the^?
chi? co' 2 thu+' nguye^n bit va` gia^y o+? dda^y.

tui ta.m da(.t ra mo^.t thu+' nguye^n cho ca'i "ddo^. mo^ pho?ng" na`y la`
"hao" (h) tu+` chu+~ "hao hao". Ca`ng "hao hao" nhie^`u thu+' thi` "ddo^.
mo^ pho?ng" ca`ng lo+'n.

Nhu+ va^.y dda~ co' the^? gia?i quye^'t dduo+.c va^'n dde^` thu+' nguye^n
cu?a 2 co^ng thu+'c E=mc^2 cu?a Prof Ngo.c. Ngoa`i ra cu~ng gia?i quye^'t
dduo+.c ca^u ho?i ba'c Tie^'n dda(.t ra vo+'i vu. ba'c Vie^.t ddo entropy,
ra(`ng ca`ng vie^1't da`i ma` i't y' thi` ca`ng dda'ng "vu+'t ddi". Nho+`
ca'c ba'c cu`ng nghi~ tie^'p.

h cu?a chu+~ "kho^ng" la` bao nhie^u? Hehe, cu+' theo sa('c kho^ng kho^ng
sa('c (ma` tui hie^1?u, chu+' kho^ng pha?i cu?a nha` Pha^.t dda^u nhe')
thi` h("kho^ng")= 8 na(`m ngang. Tui co' ho?i 1 co^ ba.n ddang la`m tie^'n
si~ ve^` va(n minh phuo+ng Ddo^ng ra(`ng chu+~ Kho^ng nha` Pha^.t va`
chu+~ Kho^ng cu?a cu. La~o kha'c gio^'ng nhau ra sao, co^ na`y no'i pha?i
la`m 1 ca'i lua^.n a'n tie^'n si~ nu+~a mo+'I no'i dduo+.c. Dda`nh kho^ng
da'm la.m ba`n.

cu~ng vi` va^.y ma` ne^'u chi? ddo HLNTC cha(?ng ha.n ba(`ng "bit" kho^ng
tho^i thi` chu+a ddu?, ma` chi? ddo ba(`ng "hao" kho^ng tho^i cu~ng
thie^'u, pha?i ddo ba(`ng ca? 2 thu+' nguye^n na`y. Mo+`i ca'c ba'c cho y'
kie1^'n.

La^m