1. OPENMP
A Brief Introduction to OpenMP
Û[U/ Jerry He
hejw06@gmail.com
June 19, 2010
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 1 / 31

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1 OpenMP0
2 OpenMPA5
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 2 / 31

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1 OpenMP0
2 OpenMPA5
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 2 / 31

4. 0
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Jerry He (Tsinghua University) A Brief Introduction to OpenMP 3 / 31

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Jerry He (Tsinghua University) A Brief Introduction to OpenMP 4 / 31

6. 0
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Jerry He (Tsinghua University) A Brief Introduction to OpenMP 5 / 31

7. 0
OpenMP0
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“èCz
<omp.h>Þ©‡
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Jerry He (Tsinghua University) A Brief Introduction to OpenMP 6 / 31

8. 0
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OpenMPS• .
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k"
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Jerry He (Tsinghua University) A Brief Introduction to OpenMP 7 / 31

9. 0
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éA OpenMP§Sp§z‡êâÑk˜‡–¯á5"
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dêâ UCéÙ§‚§ÑŒ„"
Private
z‡‚§ÑÕkdêâ"
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UC•=éd‚§Œ„"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 8 / 31

10. 0
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Jerry He (Tsinghua University) A Brief Introduction to OpenMP 9 / 31

11. 0
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M¿1«
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parallel
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¿1«pz‡‚§Ñ¬ ‰1¿
1«¥ “è"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 10 / 31

12. 0
OpenMP0
¿1«Vg
››¿1«¥‚§ êþ
%@œ¹e§¿1«S‚§
ê=XÚ¥Ø ‡ê
•{˜µset
OMP NUM THREADS=4
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 11 / 31

13. OpenMPA 5
A
OpenMP’s Hello world Program
1 #i n c l u d e <omp . h>
2 #i n c l u d e < s t d i o . h>
3 i n t main ( ) {
4 #pragma omp p a r a l l e l // come i n t o p a r a l l e l i z a t i o n
5 p r i n t f ( ” H e l l o w o r l d from t h r e a d %d , n t h r e a d s %dn” ,
6 omp get thread num () , omp get num threads () ) ;
7 } // come o u t o f p a r a l l e l i z a t i o n
ÑÑ(J
1 H e l l o w o r l d from t h r e a d 0 , n t h r e a d s 2
2 H e l l o w o r l d from t h r e a d 1 , n t h r e a d s 2
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 12 / 31

14. OpenMPA 5
A
OpenMP’s for
#pragma omp for ¦^ù‡Šé§·‚ÒŒ±r˜‡forÌ‚ óŠ
þ£~Xµ1...N¤© ‰ØÓ‚§"ù‡Šé ¡7L;‹˜
‡forÌ‚§¦UédforÌ‚ óŠþ?1© "
du 21openmp pragma¢3k 憧·‚Œ±r21½õ
1openmp pragmaÜ¿¤˜1"
1 #pragma omp p a r a l l e l
1 #pragma omp p a r a l l e l f o r
2 #pragma omp f o r
2 f o r ( i =0; i <MAX;++ i ) {
3 f o r ( i =0; i <MAX;++ i ) {
3 cout <<i <<e n d l ;
4 cout <<i <<e n d l ;
4 }
5 }
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 13 / 31

15. OpenMPA 5
A
OpenMP’s for
#pragma omp for ¦^ù‡Šé§·‚ÒŒ±r˜‡forÌ‚ óŠ
þ£~Xµ1...N¤© ‰ØÓ‚§"ù‡Šé ¡7L;‹˜
‡forÌ‚§¦UédforÌ‚ óŠþ?1© "
du 21openmp pragma¢3k 憧·‚Œ±r21½õ
1openmp pragmaÜ¿¤˜1"
1 #pragma omp p a r a l l e l
1 #pragma omp p a r a l l e l f o r
2 #pragma omp f o r
2 f o r ( i =0; i <MAX;++ i ) {
3 f o r ( i =0; i <MAX;++ i ) {
3 cout <<i <<e n d l ;
4 cout <<i <<e n d l ;
4 }
5 }
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 13 / 31

16. OpenMPA 5
A
if/shared/privateŠ{
c¡®²J OpenMP S• .§ùA‡'…i^5 ˜êâ –¯
a."
1 int x [5]={1 ,2 ,3 ,4 ,5};
2 int y [5]={2 ,3 ,4 ,5 ,6};
3 int c [5];
4 int a ,b, i ;
5 #pragma omp p a r a l l e l f o r p r i v a t e ( a , b , i ) s h a r e d ( x , y , c )
6 f o r ( i =0; i <5;++ i ) {
7 a=x [ i ] ; b=y [ i ] ;
8 c [ i ]= a+b ;
9 }
10 f o r ( i =0; i <5;++ i )
11 p r i n t f ( ”%d ” , c [ i ] ) ;
1 3 5 7 9 11
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 14 / 31

17. OpenMPA 5
A
if/shared/privateŠ{
c¡®²J OpenMP S• .§ùA‡'…i^5 ˜êâ –¯
a."
1 int x [5]={1 ,2 ,3 ,4 ,5};
2 int y [5]={2 ,3 ,4 ,5 ,6};
3 int c [5];
4 int a ,b, i ;
5 #pragma omp p a r a l l e l f o r p r i v a t e ( a , b , i ) s h a r e d ( x , y , c )
6 f o r ( i =0; i <5;++ i ) {
7 a=x [ i ] ; b=y [ i ] ;
8 c [ i ]= a+b ;
9 }
10 f o r ( i =0; i <5;++ i )
11 p r i n t f ( ”%d ” , c [ i ] ) ;
1 3 5 7 9 11
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 14 / 31

18. OpenMPA 5
A
if/shared/privateŠ{
c¡®²J OpenMP S• .§ùA‡'…i^5 ˜êâ –¯
a."
1 int x [5]={1 ,2 ,3 ,4 ,5};
2 int y [5]={2 ,3 ,4 ,5 ,6};
3 int c [5];
4 int a ,b, i ;
5 #pragma omp p a r a l l e l f o r p r i v a t e ( a , b , i ) s h a r e d ( x , y , c )
6 f o r ( i =0; i <5;++ i ) {
7 a=x [ i ] ; b=y [ i ] ;
8 c [ i ]= a+b ;
9 }
10 f o r ( i =0; i <5;++ i )
11 p r i n t f ( ”%d ” , c [ i ] ) ;
1 3 5 7 9 11
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 14 / 31

19. OpenMPA 5
A
default(none|shared)
1 int x [5]={1 ,2 ,3 ,4 ,5};
2 int y [5]={2 ,3 ,4 ,5 ,6};
3 int c [5];
4 int a ,b, i ;
5 #pragma omp p a r a l l e l f o r d e f a u l t ( s h a r e d ) p r i v a t e ( a , b , i )
6 f o r ( i =0; i <5;++ i ) {
7 a=x [ i ] ; b=y [ i ] ;
8 c [ i ]= a+b ;
9 }
10 f o r ( i =0; i <5;++ i )
11 p r i n t f ( ”%d ” , c [ i ] ) ;
%@•default(shared)§Øparallel¬S½Â CþÙ§CþÑ
•shareda."
핦^default(private)
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 15 / 31

20. OpenMPA 5
A
default(none|shared)
1 int x [5]={1 ,2 ,3 ,4 ,5};
2 int y [5]={2 ,3 ,4 ,5 ,6};
3 int c [5];
4 int a ,b, i ;
5 #pragma omp p a r a l l e l f o r d e f a u l t ( s h a r e d ) p r i v a t e ( a , b , i )
6 f o r ( i =0; i <5;++ i ) {
7 a=x [ i ] ; b=y [ i ] ;
8 c [ i ]= a+b ;
9 }
10 f o r ( i =0; i <5;++ i )
11 p r i n t f ( ”%d ” , c [ i ] ) ;
%@•default(shared)§Øparallel¬S½Â CþÙ§CþÑ
•shareda."
핦^default(private)
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 15 / 31

21. OpenMPA 5
A
firstprivate,lastprivate
1 i n t a =10 , b =20 , c =30 , d =40;
2 int i ;
3 p r i n t f ( ” a=%d , b=%d , c=%d , d=%dn” , a , b , c , d ) ;
4 #pragma omp p a r a l l e l f o r p r i v a t e ( a ) f i r s t p r i v a t e ( b , d )
la stp riv ate (c , d)
5 f o r ( i =0; i <1;++ i ) {
6 p r i n t f ( ” a=%d , b=%d c=%d , d=%dn” , a , b , c , d ) ;
7 a++;b++;c++;d++;
8 }
9 p r i n t f ( ” a=%d , b=%d , c=%d , d=%dn” , a , b , c , d ) ;
(J
1 a =10 , b =20 , c =30 , d=40
2 a =2,b=20 c =4072624 , d=40
3 a =10 , b =20 , c =4072625 , d=41
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 16 / 31

22. OpenMPA 5
A
firstprivate,lastprivate
1 i n t a =10 , b =20 , c =30 , d =40;
2 int i ;
3 p r i n t f ( ” a=%d , b=%d , c=%d , d=%dn” , a , b , c , d ) ;
4 #pragma omp p a r a l l e l f o r p r i v a t e ( a ) f i r s t p r i v a t e ( b , d )
la stp riv ate (c , d)
5 f o r ( i =0; i <1;++ i ) {
6 p r i n t f ( ” a=%d , b=%d c=%d , d=%dn” , a , b , c , d ) ;
7 a++;b++;c++;d++;
8 }
9 p r i n t f ( ” a=%d , b=%d , c=%d , d=%dn” , a , b , c , d ) ;
o(
privateCþ´™½Â "
firstprivateCþ3?¿1«c¬l ¡Ó¶CþDŠ"
lastprivateCþ3Ñ¿1«c¬DŠ ¡Ó¶Cþ"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 16 / 31

23. OpenMPA 5
A
8 reduction
1 f l o a t dot product ( f l o a t ∗ a ,
1 f l o a t dot product ( f l o a t ∗ a ,
f l o a t ∗b , i n t N) {
f l o a t ∗b , i n t N) {
2 f l o a t sum = 0 . 0 ;
2 f l o a t sum = 0 . 0 ;
3 int i ;
3 int i ;
4 #pragma omp p a r a l l e l f o r
4 #pragma omp p a r a l l e l f o r
r e d u c t i o n (+: sum ) p r i v a t e (
s h a r e d ( sum ) p r i v a t e ( i )
i)
5 f o r ( i =0; i <N;++ i )
5 f o r ( i =0; i <N;++ i )
6 sum+=a [ i ] ∗ b [ i ] ;
6 sum+=a [ i ] ∗ b [ i ] ;
7 r e t u r n sum ;
7 r e t u r n sum ;
8 }
8 }
|± 8 öŠ
+, −, ∗, /, · · ·
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 17 / 31

24. OpenMPA 5
A
8 reduction
1 f l o a t dot product ( f l o a t ∗ a ,
1 f l o a t dot product ( f l o a t ∗ a ,
f l o a t ∗b , i n t N) {
f l o a t ∗b , i n t N) {
2 f l o a t sum = 0 . 0 ;
2 f l o a t sum = 0 . 0 ;
3 int i ;
3 int i ;
4 #pragma omp p a r a l l e l f o r
4 #pragma omp p a r a l l e l f o r
r e d u c t i o n (+: sum ) p r i v a t e (
s h a r e d ( sum ) p r i v a t e ( i )
i)
5 f o r ( i =0; i <N;++ i )
5 f o r ( i =0; i <N;++ i )
6 sum+=a [ i ] ∗ b [ i ] ;
6 sum+=a [ i ] ∗ b [ i ] ;
7 r e t u r n sum ;
7 r e t u r n sum ;
8 }
8 }
|± 8 öŠ
+, −, ∗, /, · · ·
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 17 / 31

25. OpenMPA 5
A
8 reduction
1 f l o a t dot product ( f l o a t ∗ a ,
1 f l o a t dot product ( f l o a t ∗ a ,
f l o a t ∗b , i n t N) {
f l o a t ∗b , i n t N) {
2 f l o a t sum = 0 . 0 ;
2 f l o a t sum = 0 . 0 ;
3 int i ;
3 int i ;
4 #pragma omp p a r a l l e l f o r
4 #pragma omp p a r a l l e l f o r
r e d u c t i o n (+: sum ) p r i v a t e (
s h a r e d ( sum ) p r i v a t e ( i )
i)
5 f o r ( i =0; i <N;++ i )
5 f o r ( i =0; i <N;++ i )
6 sum+=a [ i ] ∗ b [ i ] ;
6 sum+=a [ i ] ∗ b [ i ] ;
7 r e t u r n sum ;
7 r e t u r n sum ;
8 }
8 }
|± 8 öŠ
+, −, ∗, /, · · ·
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 17 / 31

26. OpenMPA 5
A
.«critical
1 f l o a t d o t p r o d u c t ( f l o a t ∗ a , f l o a t ∗b , i n t N) {
2 f l o a t sum = 0 . 0 ;
3 int i ;
4 #pragma omp p a r a l l e l f o r s h a r e d ( sum ) p r i v a t e ( i )
5 f o r ( i =0; i <N;++ i )
6 #pragma omp c r i t i c a l
7 sum+=a [ i ] ∗ b [ i ] ;
8 r e t u r n sum ;
9 }
„Œ±¦^·¶ .«§½•”þ4 atomic"
ë„OpenMP(•© "
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 18 / 31

27. OpenMPA 5
A
.«critical
1 f l o a t d o t p r o d u c t ( f l o a t ∗ a , f l o a t ∗b , i n t N) {
2 f l o a t sum = 0 . 0 ;
3 int i ;
4 #pragma omp p a r a l l e l f o r s h a r e d ( sum ) p r i v a t e ( i )
5 f o r ( i =0; i <N;++ i )
6 #pragma omp c r i t i c a l
7 sum+=a [ i ] ∗ b [ i ] ;
8 r e t u r n sum ;
9 }
„Œ±¦^·¶ .«§½•”þ4 atomic"
ë„OpenMP(•© "
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 18 / 31

28. OpenMPA 5
A
?ÖNÝschedule
kn
«static,dynamic,guidedn«
NÝ•ª"
static²þ© §?Èž(
½"
dynamic§ ¤˜¬§2©˜
¬"
Ódynamic§ O3u¬ Œ
¬•ê~ "
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 19 / 31

29. OpenMPA 5
A
?ÖNÝschedule
kn
«static,dynamic,guidedn«
NÝ•ª"
static²þ© §?Èž(
½"
dynamic§ ¤˜¬§2©˜
¬"
Ódynamic§ O3u¬ Œ
¬•ê~ "
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 19 / 31

30. OpenMPA 5
A
?ÖNÝschedule
kn
«static,dynamic,guidedn«
NÝ•ª"
static²þ© §?Èž(
½"
dynamic§ ¤˜¬§2©˜
¬"
Ódynamic§ O3u¬ Œ
¬•ê~ "
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 19 / 31

31. OpenMPA 5
A
?ÖNÝschedule
kn
«static,dynamic,guidedn«
NÝ•ª"
static²þ© §?Èž(
½"
dynamic§ ¤˜¬§2©˜
¬"
Ódynamic§ O3u¬ Œ
¬•ê~ "
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 19 / 31

32. OpenMPA 5
A
?ÖNÝschedule
kn
«static,dynamic,guidedn«
NÝ•ª"
static²þ© §?Èž(
½"
dynamic§ ¤˜¬§2©˜
¬"
Ódynamic§ O3u¬ Œ
¬•ê~ "
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 19 / 31

33. OpenMPA 5
A
?ÖNÝschedule
schedule(<type> [,<chunk>])•½Ì‚NÝ•ª"
1 #pragma omp p a r a l l e l f o r s c h e d u l e ( s t a t i c )
2 ...
3 #pragma omp p a r a l l e l f o r s c h e d u l e ( dynamic , chunk )
4 ...
5 #pragma omp p a r a l l e l f o r s c h e d u l e ( g u i d e d , chunk )
6 ...
7 #pragma omp p a r a l l e l f o r s c h e d u l e ( a u t o )
8 ... // o n l y s u p p o r t by OpenMP 3 . 0 .
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 20 / 31

34. OpenMPA 5
A
section
1 #pragma omp s e c t i o n s [ c l a u s e ( s ) ]
2 {
3 #pragma omp s e c t i o n
4 <c o d e b l o c k 1 >
5 #pragma omp s e c t i o n
6 <c o d e b l o c k 2 >
7 #pragma omp s e c t i o n
8 <c o d e b l o c k 3 >
9 ...
10 }
|± clauseskµ
private firstprivate
lastprivate reduction
nowait
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 21 / 31

35. OpenMPA 5
A
section
1 #pragma omp s e c t i o n s [ c l a u s e ( s ) ]
2 {
3 #pragma omp s e c t i o n
4 <c o d e b l o c k 1 >
5 #pragma omp s e c t i o n
6 <c o d e b l o c k 2 >
7 #pragma omp s e c t i o n
8 <c o d e b l o c k 3 >
9 ...
10 }
|± clauseskµ
private firstprivate
lastprivate reduction
nowait
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 21 / 31

36. OpenMPA 5
A
barrier,nowait
1 #pragma omp p a r a l l e l
2 {
3 print (a) ;
4 #pragma omp b a r r i e r
5 print (b) ;
6 #pragma omp f o r
7 ...
8 print (c) ;
9 #pragma omp f o r n o w a i t
10 ...
11 }
Øfor §Nõ•- ¡Û¹kbarrier"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 22 / 31

37. OpenMPA 5
A
barrier,nowait
1 #pragma omp p a r a l l e l
2 {
3 print (a) ;
4 #pragma omp b a r r i e r
5 print (b) ;
6 #pragma omp f o r
7 ...
8 print (c) ;
9 #pragma omp f o r n o w a i t
10 ...
11 }
Øfor §Nõ•- ¡Û¹kbarrier"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 22 / 31

38. OpenMPA 5
A
single,master
4,¬“è•k˜‡‚§‰1"
1 #pragma omp p a r a l l e l
2 {
3 print (a) ;
4 #pragma omp s i n g l e
5 print (b) ;
6 #pragma omp m a s t e r
7 print (c) ;
8 }
singleÚmaster «O"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 23 / 31

39. OpenMPA 5
A
single,master
4,¬“è•k˜‡‚§‰1"
1 #pragma omp p a r a l l e l
2 {
3 print (a) ;
4 #pragma omp s i n g l e
5 print (b) ;
6 #pragma omp m a s t e r
7 print (c) ;
8 }
singleÚmaster «O"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 23 / 31

40. OpenMPA 5
A
single,master
4,¬“è•k˜‡‚§‰1"
1 #pragma omp p a r a l l e l
2 {
3 print (a) ;
4 #pragma omp s i n g l e
5 print (b) ;
6 #pragma omp m a s t e r
7 print (c) ;
8 }
singleÚmaster «O"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 23 / 31

41. OpenMPA 5
A
~^ Û¼ê
omp get num procs§ˆ£$1 ‚§ õ?nÅ ?nì‡ê
omp get num threads§ˆ£ c¿1«¥¹Ä ‚§‡ê
omp get thread num§ˆ£‚§Ò§XJkt‡¹Ä‚§§‚§Ò
•0 t-1"
omp set num threads§?U¿1‰1“èž‚§ ‡ê"‚§êŒ
U‡LŒ^ ?nìê§džõ‡‚§¬ N Ó˜‡?nì
þ"d¼ê7L3G1Ü© N^"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 24 / 31

42. OpenMPA 5
A
OpenMP 3.0
Task
1 v e c t o r vec (100) ;
¿1i@ 2 vector : : iterator i t ;
3 #pragma omp f o r d e f a u l t (
none ) s h a r e d ( v e c )
4 f o r ( i t =v e c . b e g i n ( ) ; i t <
v e c . end ( ) ; i t ++)
5 // do y o u r work .
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 25 / 31

43. OpenMPA 5
A
OpenMP 3.0
Task
¿1i@
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 25 / 31

44. OpenMPA 5
A
OpenMP 3.0
Task
¿1i@
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 25 / 31

45. OpenMPA 5
A
Performance:Amdahl’s law
Definition
1
speedup(p) = (1)
s + (1 − s)/p
p: core nums
s: serial code
1-s: can parallel code
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 26 / 31

46. OpenMPA 5
A
Performance:Amdahl’s law
Definition
1
speedup(p) = (1)
s + (1 − s)/p
p: core nums
s: serial code
1-s: can parallel code
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 26 / 31

47. OpenMPA 5
A
One Myth
A program use all cores can scale.
éuG1“èkvk•Ð `z"
1 double a [ 1 0 0 0 ] [ 1 0 0 0 ] ;
2 f o r ( i n t i =0; i <1000; i ++)
3 f o r ( i n t j =0; j <1000; j ++)
4 a [ i ] [ j ] = 0 . 0 // o r a [ j ] [ i ] = 0 . 0
5 // c++’ s a r r a y i s row− f i r s t .
´Ä• zÜ© Ñž"
S•§– •. . .
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 27 / 31

48. OpenMPA 5
A
One Myth
A program use all cores can scale.
éuG1“èkvk•Ð `z"
1 double a [ 1 0 0 0 ] [ 1 0 0 0 ] ;
2 f o r ( i n t i =0; i <1000; i ++)
3 f o r ( i n t j =0; j <1000; j ++)
4 a [ i ] [ j ] = 0 . 0 // o r a [ j ] [ i ] = 0 . 0
5 // c++’ s a r r a y i s row− f i r s t .
´Ä• zÜ© Ñž"
S•§– •. . .
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 27 / 31

49. OpenMPA 5
A
One Myth
A program use all cores can scale.
éuG1“èkvk•Ð `z"
1 double a [ 1 0 0 0 ] [ 1 0 0 0 ] ;
2 f o r ( i n t i =0; i <1000; i ++)
3 f o r ( i n t j =0; j <1000; j ++)
4 a [ i ] [ j ] = 0 . 0 // o r a [ j ] [ i ] = 0 . 0
5 // c++’ s a r r a y i s row− f i r s t .
´Ä• zÜ© Ñž"
S•§– •. . .
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 27 / 31

50. OpenMPA 5
A
One Myth
A program use all cores can scale.
éuG1“èkvk•Ð `z"
1 double a [ 1 0 0 0 ] [ 1 0 0 0 ] ;
2 f o r ( i n t i =0; i <1000; i ++)
3 f o r ( i n t j =0; j <1000; j ++)
4 a [ i ] [ j ] = 0 . 0 // o r a [ j ] [ i ] = 0 . 0
5 // c++’ s a r r a y i s row− f i r s t .
´Ä• zÜ© Ñž"
S•§– •. . .
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 27 / 31

51. OpenMPA 5
A
OpenMP
Demo
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 28 / 31

52. OpenMPA 5
A
o(
OpenMPJø˜‡ §%rŒ ¿1 ."
Œ^u?¿Œ •S•ªXÚ¥"
A Ü?ÈìÑ|±OpenMP"
3 ¡|±OpenMP 3.0"
OpenMP 3.0¥ taskA5¦ÙA^•2"
Sun CompileréOpenMP|±•2"
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 29 / 31

53. OpenMPA 5
A
ë•]
OpenMP(• Õ
Free lunch is over
Ruud van der Pas: An overview of OpenMP 3.0
Wikipedia OpenMP
OpenMP Application Program Interface Version 3.0 May 2008
Summary of OpenMP 3.0 C/C++ Syntax
Jerry He (Tsinghua University) A Brief Introduction to OpenMP 30 / 31

54. OpenMPA 5
A
Thanks for your attention!
Q&A
Jerry He (Tsinghua University) ã:
A Brief Introduction to OpenMP 31 / 31