paralili epe3ergasia & beowulf

[Christos Ricudis]

Hello Linux-greek-users!

Linux-greek-users wrote to I Ioannou about "paralili epe3ergasia & beowulf":

 L> ypo8eto oti sxetizetai amesa me pvm kai kapoia alla paromoia
 L> paketa, alla distixo den to polikatexo to antikeimeno
 L> yparxei kaneis pou exei asxoli8ei na mou dosei ligo idea ti
 L> pezete?

Nai. Einai ena implementation tou massively parallel programming paradigm 
basismeno sto Linux. Kai swsta ypo8eteis, h arxitektonikh einai paromoia me 
toy PVM (me thn kyria diafora oti to PVM exei multi-platform capabilities). 

To massively parallel montelo apoteleitai apo polla processing elements me 
ksexwristh gia to ka8ena mnhmh, kai ena interconnection network poy syndeei 
ta processing elements metaksy toys. O monos tropos epokoinwnias metaksy twn
processing elements einai to message passing - den yparxei koinh mnhmh. To 
pleonekthma aytoy toy montelou einai oti einai fobera scalable (eks'ou kai 
to "massively"), kai ta meionekthmata einai oti prwton to message passing
apaitei poly megalyterh prospa8eia ek merous toy programmatisth apo to 
shared memory montelo kai afeterou oti basizetai se ena interconnection 
network to opoio prepei na einai grhgoro (kai ekei htan poy yperterousan 
paradosiaka oi kataskeyastes supercomputers, mexri poy diktyakes texnologies 
opws to HIPPI kai to ATM epetrepsan thn ylopoihsh toy MPP montelou me fthna, 
grhgora workstations, kai oi kataskeyastes supercomputers xrewkophsan en mia 
nyxti). 

Anti8eta, to shared memory montelo xrhsimopoiei koinh mnhmh metaksy twn 
processing elements, ta opoia diasyndeontai metaksy toys me ena common bus. 
To programming paradigm poy xrhsimopoieitai se ayth thn periptwsh einai to 
klassiko multithreading - h yparksh koinhs mnhmhs epitrepei sta threads poy 
trexoyn en parallhlia na prospelasoun koines metablhtes toy task. To 
pleonekthma aytoy toy montelou einai h *sygkritikh* eykolia sthn ylopoihsh
toy parallhlou kwdika, afou den yparxei message passing. To meionekthma einai
oti to ena kai monadiko bus apotelei perioristiko paragonta sto scalability 
(oi shared memory mhxanes exoyn to poly mexri 16 processors synh8ws, me pio 
synh8ismena noymera 2, h 4 processors. Yparxoyn kai eksaireseis alla einai 
elaxistes). 

Ean h efarmogh poy 8eleis na xrhsimopoihseis mporei na diatypw8ei se kapoio 
SIMD (single instruction multiple data) montelo, p.x. finite element analysi, 
matrix manipulations, h genetic algorithms, KAI exeis poly kalo locality of 
reference twn dedomenwn, mporeis na xrhsimopoihseis ena beowulf h ena PVM 
me ontws ekplhktika apotelesmata sthn apodosh. O kanonas edw einai enas. Oso 
perissotero meiwseis tis apaithseis toy programmatos gia synchronization 
kai message passing, toso kalytera. 

Mia klassikh kai poly apodotikh ylopoihsh einai h pool of tasks, sthn opoia 
enas server ypodiairei to domain toy problhmatos se mikrotera tmhmata, kai 
ka8e client "zhtaei" tmhmata pros lush (akribws etsi leitourgei to RC5 
cracking contest). 

Ciao,
  Christos
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