{"id":42130,"date":"2019-03-18T00:00:00","date_gmt":"2019-03-17T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/novyj-mirovoj-rekord-po-vychisleniyu-chisla-pi-31-4-trln-znakov"},"modified":"2020-02-18T13:44:56","modified_gmt":"2020-02-18T10:44:56","slug":"novyj-mirovoj-rekord-po-vychisleniyu-chisla-pi-31-4-trln-znakov","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/administrirovanie\/novyj-mirovoj-rekord-po-vychisleniyu-chisla-pi-31-4-trln-znakov","title":{"rendered":"Ny verdensrekord i beregning af pi: 31,4 trillioner tegn","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"Ny
\n
\nBailey-Borwein-Plouffe-formlen, der g\u00f8r det muligt at udtr\u00e6kke hvilken som helst specifik hexadecimale eller bin\u00e6re cifre af tallet pi uden at beregne de foreg\u00e5ende (den nuv\u00e6rende rekord blev sat med Chudnovsky-algoritmen, se nedenfor)<\/i><\/p>\n

Google Compute Engine beregningsklynge har p\u00e5 121 dage med 25 virtuelle maskiner beregnet det st\u00f8rste antal cifre i tallet pi, og har sat en ny verdensrekord: 31,4 trillioner decimaler. Dette er f\u00f8rste gang, offentlig cloud-software blev anvendt til beregning af pi i s\u00e5 stor skala.<\/p>\n

Rekorden vil blive registreret under navnet Emma Haruka Iwao fra Googles afdeling for h\u00f8jtydende beregninger. Det var hende, der brugte Google Clouds infrastruktur til beregningerne. Den tidligere verdensrekord blev sat af Peter Trueb i 2016, hvor han beregnede tallet til 22,4 trillioner cifre. p\u00e5 en specielt designet server<\/a><\/noindex>, som ogs\u00e5 blev sponsoreret af arbejdsgiveren.
\n<\/a><\/noindex>
\nLigesom Trueb anvendte Google-ingeni\u00f8ren y-cruncher til beregningen. Dette program bruger Chudnovsky-algoritmen<\/a><\/noindex>, en hurtig algoritme til beregning af tallet pi. Allerede i 80'erne beregnede Chudnovsky-br\u00f8drene<\/a><\/noindex> ved hj\u00e6lp af det en milliard decimaler.<\/p>\n

Algoritmen er i sin tur baseret p\u00e5 egenskaben af hurtig konvergens af den hypergeometriske r\u00e6kkef\u00f8lge:<\/p>\n

\"Ny
\n
\nEmma Haruka Iwao blev fascineret af det \"magiske\" tal, da hun l\u00e6rte om det i matematikundervisningen i skolen, skriver<\/a><\/noindex> Wired<\/i>. I universitetet var en af hendes professorer, Daisuke Takahashi, rekordinnehaver for antallet af beregnede cifre ved hj\u00e6lp af en supercomputer. I dag kan n\u00e6sten enhver interesseret ingeni\u00f8r, som har adgang til betydelige beregningsressourcer og stor lagringsplads (til at gemme beregningsresultaterne), s\u00e6tte rekorder. Programmet, der blev oprettet i 2009, y-cruncher<\/a><\/noindex> er designet til at beregne matematiske konstanter som pi. Det underst\u00f8tter massiv multithreading og trillioner af r\u00e6kkevidder. Dette program har faktisk kommoditiseret beregningen af konstanter.<\/p>\n

\u00abDu har brug for en ret stor computer for at sl\u00e5 verdensrekorden,\u00bb siger Ivao. \u00abDet kan ikke lade sig g\u00f8re med en butikcomputer, s\u00e5 tidligere byggede folk specialmaskiner.\u00bb I september 2018 begyndte Ivao at overveje, hvordan den tekniske beregningsproces ville fungere uden for rekordomr\u00e5det. Det blev hurtigt klart, at den st\u00f8rste udfordring ville v\u00e6re datam\u00e6ngden, der skulle opbevares. Resultatet viste sig at fylde 170 terabyte. I stedet for at samle en specialserver som sine forg\u00e6ngere brugte hun Googles Cloud-infrastruktur.<\/p>\n

\"NyIvao oprettede 25 virtuelle maskiner: \u00abMen i stedet for at trykke p\u00e5 knappen for den virtuelle maskine 25 gange, automatiserede jeg det,\u00bb forklarer hun. \u00abDu kan g\u00f8re det p\u00e5 et par minutter, men hvis du har brug for s\u00e5 mange computere, vil det tage flere dage at f\u00e5 det hele sat op.\u00bb Derefter styrede Ivao kontinuerligt y-cruncher p\u00e5 disse 25 virtuelle maskiner i 121 dage. <\/p>\n

For at sikre beregningernes n\u00f8jagtighed skulle de virtuelle maskiner k\u00f8re konstant. Ingeni\u00f8ren installerede et overv\u00e5gningssystem, der ville advare hende, hvis der skete noget, f.eks. et pludseligt nedbrud p\u00e5 en af de virtuelle maskiner. Bare \u00e9n ulykke \u2013 selv i et par minutter \u2013 kunne true hele beregningsprocessen, hvis der ikke var en sikkerhedskopi.<\/p>\n

\u00abKranchen og Google Cloud har backupsystemer, og jeg har konfigureret dem, s\u00e5 du kan tage \u00f8jebliksbilleder af disse diske uden at stoppe beregningerne,\u00bb siger Ivao. Disse data blev derefter kopieret og gemt eksternt p\u00e5 andre diske som snapshots.<\/p>\n

\u00abI starten var der flere parametre, som jeg \u00e6ndrede, f.eks. hvor mange data du kunne l\u00e6se eller skrive ad gangen, og hvordan gr\u00e6nserne ville \u00e6ndre sig, n\u00e5r m\u00e6ngden steg,\u00bb siger Ivao.<\/p>\n

Med det stigende antal cifre voksede filst\u00f8rrelsen, og kompleksiteten af beregningerne steg nonlinear. Dette komplicerede den oprindelige beregning, da Ivao fors\u00f8gte at beregne, hvilken ressource kapacitet de virtuelle maskiner ville kr\u00e6ve til projektet.<\/p>\n

Beregnings- og resultattjekket er nu afsluttet: y-cruncher har to grundl\u00e6ggende algoritmer indbygget \u2013 en til at beregne selve pi, og en anden til at tjekke. Tjekalgoritmen arbejder parallelt med beregningen, men beregner kun \u00e9t ciffer, s\u00e5 rekorden kan registreres officielt.<\/p>\n

\nTeoretisk set kan en ny verdensrekord s\u00e6ttes ved blot at tage den tidligere fil og anvende Bailey\u2013Borwein\u2013Plouffe-formlen til at beregne endnu et ciffer. Men det strider sikkert imod reglerne for registrering af s\u00e5danne verdensrekorder: sandsynligvis skal hver ans\u00f8ger starte beregningen fra begyndelsen. En mulighed er at forbedre den tidligere pr\u00e6station med N %, hvilket ikke kan g\u00f8res med Bailey\u2013Borwein\u2013Plouffe-formlen.<\/p>\n

Kilde: habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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\u0437\u043d\u0430\u043a\u043e\u0432 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":42131,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[688],"tags":[],"class_list":["post-42130","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-administrirovanie"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Ny verdensrekord for beregning af pi: 31,4 trillioner cifre | 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