{"id":10312,"date":"2021-11-21T19:48:06","date_gmt":"2021-11-21T12:48:06","guid":{"rendered":"https:\/\/www.vietlearn.org\/post\/?p=10312"},"modified":"2021-11-21T20:11:23","modified_gmt":"2021-11-21T13:11:23","slug":"tai-sao-lai-xay-ra-su-bung-no-to-hop-thong-tin","status":"publish","type":"post","link":"https:\/\/www.vietlearn.org\/kien-thuc\/tai-sao-lai-xay-ra-su-bung-no-to-hop-thong-tin\/","title":{"rendered":"T\u1ea1i sao l\u1ea1i x\u1ea3y ra s\u1ef1 b\u00f9ng n\u1ed5 t\u1ed5 h\u1ee3p th\u00f4ng tin?"},"content":{"rendered":"\n

Kh\u00f4ng bi\u1ebft b\u1ea1n \u0111\u00e3 nghe th\u1ea5y chuy\u1ec7n th\u00f4ng tin t\u0103ng nhanh \u0111\u1ed9t bi\u1ebfn d\u1eabn t\u1edbi s\u1ef1 “b\u00f9ng n\u1ed5” ch\u01b0a. \u0110\u00f3 l\u00e0 chuy\u1ec7n g\u00ec v\u1eady? H\u00e3y xem m\u1ed9t v\u00ed d\u1ee5 \u0111\u01a1n gi\u1ea3n sau \u0111\u00e2y.<\/p>\n\n\n\n

C\u00f3 m\u1ed9t t\u1ea5m b\u1ea3n \u0111\u1ed3 th\u00e0nh ph\u1ed1, ng\u01b0\u1eddi b\u00e1n h\u00e0ng c\u1ea7n ph\u1ea3i \u0111i h\u1ebft c\u00e1c th\u00e0nh ph\u1ed1, v\u00e0 ch\u1ec9 \u0111i t\u1edbi m\u1ed9t l\u1ea7n. Trong b\u1ea3n \u0111\u1ed3, c\u1ee9 gi\u1eefa hai th\u00e0nh ph\u1ed1 l\u00e0 c\u00f3 m\u1ed9t con \u0111\u01b0\u1eddng, tr\u00ean \u0111\u00f3 ghi r\u00f5 kho\u1ea3ng c\u00e1ch hai b\u00ean. Y\u00eau c\u1ea7u thi\u1ebft k\u1ebf<\/a> m\u1ed9t h\u00e0nh tr\u00ecnh cho ng\u01b0\u1eddi b\u00e1n h\u00e0ng n\u1ecd, sao cho xu\u1ea5t ph\u00e1t t\u1eeb b\u1ea5t k\u1ec3 th\u00e0nh ph\u1ed1 n\u00e0o trong s\u1ed1 c\u00e1c th\u00e0nh ph\u1ed1 \u0111\u00f3, v\u00e0 r\u1ed3i khi quay l\u1ea1i th\u00e0nh ph\u1ed1 ban \u0111\u1ea7u th\u00ec \u0111\u00f3 l\u00e0 h\u00e0nh tr\u00ecnh ng\u1eafn nh\u1ea5t. \u0110\u00f3 ch\u00ednh l\u00e0 “b\u00e0i to\u00e1n ng\u01b0\u1eddi b\u00e1n h\u00e0ng”.<\/p>\n\n\n\n

Y\u00eau c\u1ea7u gi\u1ea3i \u0111\u1ec1 to\u00e1n n\u00e0y c\u00f3 v\u1ebb kh\u00f4ng kh\u00f3, ch\u1ec9 c\u1ea7n t\u00ecm ra c\u00e1c con \u0111\u01b0\u1eddng tr\u00ean b\u1ea3n \u0111\u1ed3, r\u1ed3i so s\u00e1nh, ch\u1ecdn con \u0111\u01b0\u1eddng ng\u1eafn nh\u1ea5t l\u00e0 xong. N\u1ebfu s\u1ed1 l\u01b0\u1ee3ng th\u00e0nh ph\u1ed1 \u00edt th\u00ec c\u00e1ch th\u1ee9c \u0111\u00f3 l\u00e0 kh\u1ea3 thi v\u00e0 thi\u1ebft th\u1ef1c. Th\u1ebf nh\u01b0ng, n\u1ebfu s\u1ed1 l\u01b0\u1ee3ng th\u00e0nh ph\u1ed1 l\u00e0 nhi\u1ec1u th\u00ec ph\u01b0\u01a1ng ph\u00e1p n\u00e0y s\u1ebd th\u1ea5t b\u1ea1i. N\u1ebfu s\u1ed1 th\u00e0nh ph\u1ed1 l\u00e0 N, th\u00ec nh\u1eefng con \u0111\u01b0\u1eddng kh\u00e1c nhau gi\u1eefa c\u00e1c th\u00e0nh ph\u1ed1 l\u00e0 N! (giai th\u1eeba N) (N! = 1x2x3x\u2026x N) \u0111\u01b0\u1eddng. N\u1ebfu vi\u1ec7c t\u00ednh to\u00e1n \u0111\u1ed9 d\u00e0i m\u1ed9t con \u0111\u01b0\u1eddng m\u1ea5t \u0111i th\u1eddi gian l\u00e0 0,1 micr\u00f4 gi\u00e2y (10-7 gi\u00e2y) th\u00ec ph\u1ea3i s\u1eed d\u1ee5ng s\u1ed1 th\u1eddi gian l\u00e0 N! x 0,1 micr\u00f4 gi\u00e2y \u0111\u1ec3 t\u00ednh ra \u0111\u1ed9 d\u00e0i c\u1ee7a t\u1ea5t c\u1ea3 c\u00e1c con \u0111\u01b0\u1eddng. Trong c\u00f4ng vi\u1ec7c th\u1ef1c t\u1ebf, \u0111\u00f2i h\u1ecfi ng\u01b0\u1eddi b\u00e1n h\u00e0ng ph\u1ea3i \u0111i th\u0103m h\u1ecfi 24 th\u00e0nh ph\u1ed1 th\u00ec c\u0169ng kh\u00f4ng ph\u1ea3i vi\u1ec7c g\u00ec k\u00ec l\u1ea1 l\u1eafm.<\/p>\n\n\n\n

Nh\u01b0ng 24! th\u00ec l\u1ea1i l\u1edbn qu\u00e1 ch\u1eebng. T\u1ed5ng l\u01b0\u1ee3ng th\u1eddi gian d\u00e0nh cho vi\u1ec7c t\u00ednh to\u00e1n \u0111\u1ed9 d\u00e0i c\u00e1c con \u0111\u01b0\u1eddng n\u1ed1i 24 th\u00e0nh ph\u1ed1 l\u00e0 24! x 0,1 micr\u00f4 gi\u00e2y (t\u1ee9c 6,24484017 x 1022 micr\u00f4, kho\u1ea3ng 1960 tri\u1ec7u n\u0103m). B\u1edfi v\u1eady, n\u1ebfu N c\u1ed9ng th\u00eam 1, t\u1ee9c 24 + 1= 25 th\u00ec th\u1eddi gian ti\u00eau ph\u00ed s\u1ebd t\u0103ng 25 l\u1ea7n, t\u1ee9c l\u00e0 25 x 0,1 micr\u00f4 gi\u00e2y (kho\u1ea3ng 49050 tri\u1ec7u n\u0103m). N t\u0103ng th\u00eam 1 th\u00ec l\u01b0\u1ee3ng th\u1eddi gian t\u0103ng (N + 1) l\u1ea7n. T\u1ed1c \u0111\u1ed9 t\u0103ng tr\u01b0\u1edfng t\u0103ng \u0111\u1ed9t bi\u1ebfn khi\u1ebfn ta kh\u00f3 h\u00ecnh dung \u0111\u01b0\u1ee3c. Hi\u1ec7n t\u01b0\u1ee3ng n\u00e0y ch\u00ednh l\u00e0 v\u1ea5n \u0111\u1ec1 “b\u00f9ng n\u1ed5 t\u1ed5 h\u1ee3p”.<\/p>\n\n\n\n

C\u00f2n m\u1ed9t s\u1ed1 v\u1ea5n \u0111\u1ec1 g\u1ecdi l\u00e0 v\u1ea5n \u0111\u1ec1 \u0111\u00e1nh c\u1edd, n\u1ebfu ng\u01b0\u1eddi \u0111\u00e1nh c\u1edd v\u1edbi m\u00e1y, \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o cu\u1ed1i c\u00f9ng s\u1ebd th\u1eafng th\u00ec m\u00e1y t\u00ednh c\u00f3 th\u1ec3 ph\u1ea3i th\u1eed c\u00e1ch \u0111i c\u1ee7a m\u1ecdi kh\u1ea3 n\u0103ng, r\u1ed3i \u0111\u00f3 m\u00e0 ch\u1ecdn l\u1ea5y c\u00e1ch \u0111i \u0111\u1ec3 th\u1eafng. M\u1ed7i l\u1ea7n th\u1eed nghi\u1ec7m m\u1ed9t n\u01b0\u1edbc c\u1edd th\u00ec l\u1ea1i c\u00f3 m\u1ed9t th\u1ebf c\u1edd, m\u00e0 s\u1ed1 l\u01b0\u1ee3ng th\u1ebf c\u1edd l\u00e0 r\u1ea5t nhi\u1ec1u. V\u00ed d\u1ee5 c\u1edd vua c\u00f3 l\u01b0\u1ee3ng th\u1ebf c\u1edd l\u00e0 10120, c\u00f2n c\u1edd v\u00e2y l\u00e0 10761.<\/p>\n\n\n\n

T\u1ea5t c\u1ea3 nh\u1eefng c\u00e1ch \u0111i c\u00f3 th\u1ec3 \u0111\u1ec1u th\u1eed m\u1ed9t l\u1ea7n, sau \u0111\u00f3 ch\u1ecdn ra ph\u01b0\u01a1ng \u00e1n hay nh\u1ea5t l\u00e0 c\u00f3 th\u1ec3 l\u00e0m \u0111\u01b0\u1ee3c. Nh\u01b0ng th\u1eddi gian \u0111\u1ec3 l\u00e0m nh\u01b0 v\u1eady v\u00e0 kh\u00f4ng gian l\u01b0u tr\u1eef th\u00ec th\u1eadt l\u00e0 kinh kh\u1ee7ng. V\u1edbi n\u0103ng l\u1ef1c c\u1ee7a m\u00e1y t\u00ednh hi\u1ec7n nay m\u00e0 gi\u1ea3i b\u00e0i to\u00e1n kh\u00f3 n\u00e0y l\u00e0 kh\u00f4ng th\u1ec3. B\u1edfi v\u00ec m\u00e1y t\u00ednh n\u00e0o th\u00ec b\u1ed9 nh\u1edb c\u1ee7a n\u00f3 c\u0169ng ch\u1ec9 c\u00f3 dung l\u01b0\u1ee3ng c\u00f3 h\u1ea1n, kh\u00f4ng th\u1ec3 v\u00f4 h\u1ea1n \u0111\u01b0\u1ee3c. B\u1ea5t k\u00ec \u0111\u1ed9ng t\u00e1c n\u00e0o c\u1ee7a m\u00e1y \u0111\u1ec1u c\u1ea7n m\u1ed9t th\u1eddi gian nh\u1ea5t \u0111\u1ecbnh \u0111\u1ec3 ho\u00e0n th\u00e0nh.<\/p>\n\n\n\n

\u0110\u1ec3 cho d\u1ec5 hi\u1ec3u, ch\u00fang ta h\u00e3y suy x\u00e9t v\u1ea5n \u0111\u1ec1 “b\u00f9ng n\u1ed5 t\u1ed5 h\u1ee3p” theo gi\u00e1c \u0111\u1ed9 ti\u00eau ph\u00ed th\u1eddi gian cho m\u00e1y t\u00ednh \u0111\u00e1nh c\u1edd.<\/p>\n\n\n\n

Hi\u1ec7n nay t\u1ed1c \u0111\u1ed9 t\u00ednh to\u00e1n c\u1ee7a m\u00e1y t\u00ednh c\u00f3 th\u1ec3 \u0111\u1ea1t t\u1edbi 100 tri\u1ec7u l\u1ec7nh m\u1ed7i ng\u00e0y. D\u00f9ng ch\u01b0\u01a1ng tr\u00ecnh \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf<\/a> hay nh\u1ea5t, \u0111i m\u1ed9t n\u01b0\u1edbc c\u1edd th\u00ec ph\u1ea3i ch\u1ea5p h\u00e0nh 10 l\u1ec7nh. Nh\u01b0 v\u1eady, \u0111i m\u1ed9t n\u01b0\u1edbc th\u00ec m\u1ea5t 0,1 micr\u00f4 gi\u00e2y.<\/p>\n\n\n\n

T\u1ed1c \u0111\u1ed9 m\u00e1y t\u00ednh c\u00f3 th\u1ec3 \u0111\u1ea1t t\u1edbi \u01b0\u1edbc ch\u1eebng 2 miligi\u00e2y\/b\u01b0\u1edbc (1 ms = 10-3 s). T\u1ed1c \u0111\u1ed9 t\u1ed1i \u0111a v\u1ec1 l\u00ed thuy\u1ebft cho m\u00e1y t\u00ednh c\u1ed5ng tu\u1ea7n t\u1ef1 (serial m\u00e1y t\u00ednh) l\u00e0 10-12 mili gi\u00e2y\/b\u01b0\u1edbc, c\u00f2n t\u1ed1c \u0111\u1ed9 gi\u1edbi h\u1ea1n cho lo\u1ea1i m\u00e1y t\u00ednh c\u1ed5ng song song (parallel m\u00e1y t\u00ednh) l\u00e0 10-11 ms\/b\u01b0\u1edbc, ho\u1eb7c 10-104 n\u0103m\/1 b\u01b0\u1edbc \u0111i.<\/p>\n\n\n\n

D\u00f9 cho t\u00ednh to\u00e1n v\u1edbi t\u1ed1c \u0111\u1ed9 l\u00ed thuy\u1ebft t\u1ed1i \u0111a tr\u00ean m\u00e1y t\u00ednh c\u1ed5ng song song th\u00ec vi\u1ec7c t\u00ecm nghi\u1ec7m cho c\u1edd vua ph\u1ea3i m\u1ea5t 10 ng\u00e0n t\u1ec9 n\u0103m (1016) m\u1edbi c\u00f3 th\u1ec3 ho\u00e0n th\u00e0nh. Th\u1ebf nh\u01b0ng, ch\u00fang ta bi\u1ebft r\u1eb1ng l\u1ecbch s\u1eed V\u0169 Tr\u1ee5 c\u0169ng ch\u1ec9 m\u1edbi l\u00e0 15 t\u1ec9 n\u0103m th\u00f4i.<\/p>\n\n\n\n

T\u1eeb kh\u00f3a: B\u00f9ng n\u1ed5 t\u1ed5 h\u1ee3p th\u00f4ng tin; B\u00e0i to\u00e1n ng\u01b0\u1eddi b\u00e1n h\u00e0ng; Ti\u00eau ph\u00ed th\u1eddi gian.<\/p>\n","protected":false},"excerpt":{"rendered":"

Kh\u00f4ng bi\u1ebft b\u1ea1n \u0111\u00e3 nghe th\u1ea5y chuy\u1ec7n th\u00f4ng tin t\u0103ng nhanh \u0111\u1ed9t bi\u1ebfn d\u1eabn t\u1edbi s\u1ef1 “b\u00f9ng n\u1ed5” ch\u01b0a. \u0110\u00f3 l\u00e0 chuy\u1ec7n g\u00ec v\u1eady? H\u00e3y xem m\u1ed9t v\u00ed d\u1ee5 \u0111\u01a1n gi\u1ea3n sau \u0111\u00e2y. C\u00f3 m\u1ed9t t\u1ea5m b\u1ea3n \u0111\u1ed3 th\u00e0nh ph\u1ed1, ng\u01b0\u1eddi b\u00e1n h\u00e0ng c\u1ea7n ph\u1ea3i \u0111i h\u1ebft c\u00e1c th\u00e0nh ph\u1ed1, v\u00e0 ch\u1ec9 \u0111i t\u1edbi m\u1ed9t […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15,13],"tags":[],"class_list":["post-10312","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc","category-tin-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/10312","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=10312"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/10312\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=10312"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=10312"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=10312"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}