CSC/ECE 506 Spring 2010/ch 3 yl: Difference between revisions

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===DOACROSS===
===DOACROSS===
'''for'''    i:=2:N-1 '''do''' A(i):=[A(i-1) + A(i) + A(i+1)]/3; '''next''' i;
'''forall''' i:=2:N-1 '''do''' A(i):=[A(i-1) + A(i) + A(i+1)]/3;


  '''for''' (i=1; i<=N; i++) {
  '''for''' (i=1; i<=N; i++) {
Line 29: Line 27:
  '''for''' (i=1; i<=N; i++) {
  '''for''' (i=1; i<=N; i++) {
   '''S2''': a[i] = a[i-1] + temp[i];}'''
   '''S2''': a[i] = a[i-1] + temp[i];}'''
'''post(0);'''
'''for''' (i=1; i<=N; i++) {
  '''S1:''' temp[i] = b[i] * c[i];}
'''for''' (i=1; i<=N; i++) {
  '''S2''': a[i] = a[i-1] + temp[i];}'''


[[Image:DOACROSS.jpg]]
[[Image:DOACROSS.jpg]]

Revision as of 20:19, 20 February 2010

Supplement to Chapter 3: Support for parallel-programming models. Discuss how DOACROSS, DOPIPE, DOALL, etc. are implemented in packages such as Posix threads, Intel Thread Building Blocks, OpenMP 2.0 and 3.0.

Parallel-programming models

Loop-independent vs. loop-carried dependences

Loop-independent

Loop-carried dependences

DOALL

for    i:=2:N-1 do A(i):=[A(i-1) + A(i) + A(i+1)]/3; next i;
forall i:=2:N-1 do A(i):=[A(i-1) + A(i) + A(i+1)]/3;

for (i=2; i<=n; i+=2)
 s: a[i] = a[i-2];
for (i=3; i<=n; i+=2)
 s: a[i] = a[i-2];

DOACROSS

for (i=1; i<=N; i++) {
 S: a[i] = a[i-1] + b[i] * c[i];}

for (i=1; i<=N; i++) {
  S1: temp[i] = b[i] * c[i];}
for (i=1; i<=N; i++) {
  S2: a[i] = a[i-1] + temp[i];}

post(0);
for (i=1; i<=N; i++) {
  S1: temp[i] = b[i] * c[i];}
for (i=1; i<=N; i++) {
  S2: a[i] = a[i-1] + temp[i];}

DOPIPE

Implementation

References

  1. wikipedia: Parallel Computing
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