I Doi vdi may Turing khong tat dinh diing N, quat rinh tinh toan trgn moi t i i vao w duqc dien ra theo mot nhanh nao do ma may lua
Chiing minh Dinh ly 2.3.3 bSng kigm chufng Tg,p chiing c
(=^). Gia s\i L IS, ngon ngu: tren bang chu: S vk dudc khing dinh bcii may Turing khong tat dinh iV thdi gian n^. Dg chiing to L bcii may Turing khong tat dinh iV thdi gian n^. Dg chiing to L
la ngon ngii kilm chiing dUdc trong thdi gian da thiic, cac chiing cii se duoc lay tir Ej, tap tat ca cac tii khac rong trgn bang chU cii se duoc lay tir Ej, tap tat ca cac tii khac rong trgn bang chU
Erf = {1, 2,..., c/}, trong do d la so toi da cac kha nang lua chon
cua may Á' tai moi thdi digm hoat dong. Nhu da neu trong chiing
minh cac Dinh ly 1.2.4 vk 2.1.4, moi nhanh tinh todn cua N dgu
ling vdi mot tiJt nao do thuoc Ej. .
Khi do may kigm chiing thdi gian da thiic V doi vdi ngon ngfl: Jy
dugc xay dung nhu saụ
2.3 May Turing khong tat dinh thdi_cmrn^n thUc
V = "Tren m6i tir v^o (w, c), trong do u; € E* vk c e vdi dO
dai |c| < \w\^:
1. Mo phong tinh toan cua TV tren tU v^o w theo nhanh c. 2. Neu theo do dan den hinh thai chap nhan cua Á', thi chap 2. Neu theo do dan den hinh thai chap nhan cua Á', thi chap
nhan; nguoc lai, bdc bọ"
(4=). Gia sii ngon ngU L dugc kilm chiing trong thdi gian hdi may V theo tap chiing cii C. Khi do may Turing khong tit dinh TV, may V theo tap chiing cii C. Khi do may Turing khong tit dinh TV, khang dinh ngon ngfl L trong thdi gian da thiic, duoc xay dung
nhu saụ
N = "Trgn moi tit vao w:
1. Chon mot each khong tat dinh chiing eii c trong tap C
vdi do dai |c <
2. Dung V de tinh toan trgn til {w,c).
3. Neu V chap nhan, thi chap nhg.n; nguoc lai, bdc fid."
Dinh ly dude chiing minh. •
Dinh ly 2.3.5 chiing to rang NP triing vdi Idp cdc ngon ngfl
kiem chflng dUdc trong thdi gian da thflc. Vi the, dl khang dinh
mot ngon ngfl nao do thuoc Idp NP, thay vi phai xay dung mdy
Turing khong tat dinh dg khing dinh ngon ngfl ay, ta c6 the sfl dung may Turing tat dinh thdi gian da thflc de kiim tra tfl vko dung may Turing tat dinh thdi gian da thflc de kiim tra tfl vko
theo nhflng chflng cfl thich hdp.
Thi du, doi vdi ngon ngfl DIHAMPATH thuoc NP nhu da dudc
bi^t dgn trong Dinh ly 2.3.3, ta c6 thi xay dung mot may kilm
chflng doi vdi ngon ngfl nkỵ
Chiing minh Dinh ly 2.3.3 bSng kigm chufng. Tg,p chiing cii