Re^2: Re^2: Re^2: Crack pano se paralili mixani

[Sifalakis Manolis]

CLAP CLAP CLAP CLAP ...... ( *APPLAUSE* )...

 Sygxarhthria gia to thread kai thanks gia to seminar....
 DEN EIRONEYOMAI... kairo eixe na *paixtei* kati toso epimorfwtiko kai
endiaferon
 (kata tin gnwmi mou) sti lista...

 Manolis
 (.WILLY)


Christos Ricudis wrote:
> 
> Hello Linux-greek-users!
> 
> Linux-greek-users wrote to All about "Re: Re^2: Re^2: Crack pano se paralili
> 
>  L> Hmm mallon Xristo, den katalaves kati se ayto pou eixa pei 7
>  L> messages prin. Otan ena Leitourgiko ( p.x Linux), anagnorizei
>  L> kai tis 16CPU, tote kanonizei mono tou posson xronon tha
>  L> xrisimopoisei stin ka8e mia, an xreiazetai na xrisimopoiisei,
>  L> kai to possosto pou 8a xrisimopoiisei.
> 
> Esy den katalabes kala :^)
> 
> To leitourgiko systhma diaxeirizetai *PROCESSES*. Ante, to poly poly *threads*
> (poy sthn periptwsh toy linux einai to ena kai to ayto). To ka8e ena apo ayta
> trexei seiriaka se ena epeksergasth. Mporei isws na metakomisei se allon
> epeksergasth apo ayton poy ksekinhse, alla kai pali 8a trexei MONO se enan.
> Einai douleia toy PROGRAMMATISTH na ka8orisei ti kai pws kai poy 8a ektelestei
> parallhla.
> 
> Pare gia paradeigma ton pollaplasiasmo dyo n*n pinakwn poy ginetai sto parakatw
> loop :
> 
> for (i=0;i<n;i++) {
>         for (j=0;j<n;j++) {
>                 c[i][j]=0;
>                 for (k=0;k<n;k++) {
>                         c[i][j]+=a[i][k]+b[k][j];
>                 }
>         }
> }
> 
> Etsi opws to egrapsa, apotelei ENA thread. Auto shmainei oti oloi oi
> ypologismoi ekteloyntai seiriaka, se enan kai mono processor, se xrono O(n^3).
> An kanoyme ena loop unroll, blepontas thn akoloy8ia entolwn poy ektelei o
> epeksergasths katalhgoume se kati san to parakatw (poy apotelei kai ton orismo
> toy pollaplasiasmoy pinakwn) :
> 
> c[0][0]=a[0][0]*b[0][0]+a[0][1]*b[1][0]+a[0][2]*b[2][0]......
> c[0][1]=a[0][0]*b[1][0]+a[0][1]*b[1][1]+a[0][2]*b[2][1]......
> 
> Parathroume edw pera oti o ypologismos toy c[0][1] einai ypologistika
> aneksarthtos apo thn ypologismo toy c[0][0], kai den exoyme leitourgikes
> eksarthseis metaksy twn apotelesmatwn (tetoioi ypologismoi einai loykoumi gia
> parallhlous epeksergastes). Mporoyme loipon na baloyme ka8e epeksergasth
> toy systhmatos na ektelesei aneksarthta ton pollaplasiasmo ka8e dianysmatos :
> 
> for (i=0;i<n;i++) {
>         for (j=0;j<n;j++) {
>                 if (thread-fork()) {
>                         c[i][j]=0;
>                         for (k=0;k<n;k++) {
>                                 c[i][j]+=a[i][k]+b[k][j];
>                         }
>                 }
>         }
> }
> 
> (oxi, den yparxei tetoia synarthsh, to paradeigma einai fantastiko - den apexei
> omws poly apo thn pragmatikothta). Estw oti h thread-fork() kanei oti kai h
> fork(), dhladh dhmiourgei ena kainoyrio process (...thread...) alla
> to ektelei se DIAFORETIKO epeksergasth. se xrono - telika - O(n^2).
> 
> Ayto mporoume na to kanoyme mono kai mono epeidh ontas se mia Shared Memory
> multiprocessor arxitektonikh, oloi oi epeksergastes exoyn koinh prosbash
> stoys pinakes a,b,c.
> 
> An omws briskomaste se mia Distributed Memory arxitektonikh, sthn opoia DEN
> yparxei koinh mnhmh, prpeei na METAFEROUME ola ta dedomena ston kainoyrio
> processor :
> 
> for (i=0;i<n;i++) {
>         for (j=0;j<n;j++) {
>                 c[i][j]=0;
>                 if (id=fork-mpp-thread()==0) {
>                         RECEIVE(n);
>                         RECEIVE(i);
>                         RECEIVE(j);
>                         for (k=0;k<n;k++) {
>                                 RECEIVE(a[i][k]);RECEIVE(b[k][j]);
>                                 c[i][j]+=a[i][k]+b[k][j];
>                         }
>                } else {
>                         SEND(id,n);
>                         SEND(id,i);
>                         SEND(id,j);
>                         for (k=0;k<n;k++) {
>                                 SEND(id,a[i][k]);SEND(b[i][k]);
>                         }
> 
>                }
>         }
> }
> 
> ean ypo8esoume oti h RECEIVE(var) pairnei mia timh apo to parent process kai h
> SEND(pid,var) stelnei mia timh sto child process pid. (to paradeigma einai pali
> eikoniko, ta primitives einai diaforetika sthn praksh).
> 
> S'ayth thn periptwsh exoyme ton kindyno ean to n einai poly mikro, o
> ypologismos toy vector product na parei LIGOTERO xrono apo ayton poy apaiteitai
> gia th diadosh twn dedomenwn metaksy twn processors - opote h apodosh toy
> programmatos peftei anti na ayksanetai.
> 
> Estw twra oti to problhma mas einai o ypologismos mias akoloy8ias
> ths morfhs :
> 
> t(1)=f(1);
> t(n)=2*t(n-1)+f(n);           (gia n>1);
> 
> Edw de mporoume na xrhsimopoihsoume parallhlh epeksergasia - to problhma
> einai ill-conditioned, dioti o ypologismos toy t(n) *proypo8etei* ton
> ypologismo toy t(n-1).
> 
> Se periptwsh megalwn kai periplokwn programmatwn, isxoyn oi nomoi toy Amdahl
> kai Gustafson-Barsis, poy lene panw - katw oti h aykshsh sthn apodosh enos
> programmatos me parallhlismo exei ena anwtato orio poy eksartatai apo to
> pososto toy programmatos poy prepei na ektelestei seiriaka.
> 
> (ouf!)
> 
> Ciao,
>   Christos
> --

-- 
	--------------------------------------------------
	Sifalakis Manolis  (WILLY)
	e-mail: msifa at ariadne-t.gr       ARIADNE-T NOC
	   tel: +30 01 6544279          NCSR DEMOKRITOS
	--------------------------------------------------
--
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