matlab parfor pool 多核 并行 example 二层for

meatball1982

实际上,matlab自身的并行已经挺好了.
许多的函数,不用设置,就可以并行.但有时,有些东西要自己写.

我的机器是四核的.打开两个,剩下一个用来控制,(也可以打开四个,进程里就有５个matlab了.)
我的matlab
8.5.0.197613 (R2015a)
注意,符值那为什么不行.因为floor?

二层for的话,用一个ind代替.
用parfor来算,再转化.

1. clear all
   
2. clc
   
3. 
   
4. poolobj=parpool('local',2)
   
5. 
   
6. parfor i=1:8
   
7.     i
   
8.     i*2-1.5
   
9.     floor(i*2-1.5)
   
10.     disp('----this should have smothing below ')
    
11.     j=floor(i*2-1.5)
    
12.     disp('----this should have smothing up')
    
13. 
    
14. end
    
15. 
    
16. delete(poolobj)

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1. 
   

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1. Starting parallel pool (parpool) using the 'local' profile ... connected to 2 workers.
   
2. 
   
3. poolobj =
   
4. 
   
5. Pool with properties:
   
6. 
   
7.             Connected: true
   
8.            NumWorkers: 2
   
9.               Cluster: local
   
10.         AttachedFiles: {}
    
11.           IdleTimeout: 30 minute(s) (30 minutes remaining)
    
12.           SpmdEnabled: true
    
13. 
    
14. 
    
15. ans =
    
16. 
    
17.      6
    
18. 
    
19. 
    
20. ans =
    
21. 
    
22.    10.5000
    
23. 
    
24. 
    
25. ans =
    
26. 
    
27.     10
    
28. 
    
29. ----this should have smothing below
    
30. ----this should have smothing up
    
31. 
    
32. ans =
    
33. 
    
34.      5
    
35. 
    
36. 
    
37. ans =
    
38. 
    
39.     8.5000
    
40. 
    
41. 
    
42. ans =
    
43. 
    
44.      8
    
45. 
    
46. ----this should have smothing below
    
47. ----this should have smothing up
    
48. 
    
49. ans =
    
50. 
    
51.      4
    
52. 
    
53. 
    
54. ans =
    
55. 
    
56.     6.5000
    
57. 
    
58. 
    
59. ans =
    
60. 
    
61.      6
    
62. 
    
63. ----this should have smothing below
    
64. ----this should have smothing up
    
65. 
    
66. ans =
    
67. 
    
68.      3
    
69. 
    
70. 
    
71. ans =
    
72. 
    
73.     4.5000
    
74. 
    
75. 
    
76. ans =
    
77. 
    
78.      4
    
79. 
    
80. ----this should have smothing below
    
81. ----this should have smothing up
    
82. 
    
83. ans =
    
84. 
    
85.      2
    
86. 
    
87. 
    
88. ans =
    
89. 
    
90.     2.5000
    
91. 
    
92. 
    
93. ans =
    
94. 
    
95.      2
    
96. 
    
97. ----this should have smothing below
    
98. ----this should have smothing up
    
99. 
    
100. ans =
     
101. 
     
102.      1
     
103. 
     
104. 
     
105. ans =
     
106. 
     
107.     0.5000
     
108. 
     
109. 
     
110. ans =
     
111. 
     
112.      0
     
113. 
     
114. ----this should have smothing below
     
115. ----this should have smothing up
     
116. 
     
117. ans =
     
118. 
     
119.      7
     
120. 
     
121. 
     
122. ans =
     
123. 
     
124.    12.5000
     
125. 
     
126. 
     
127. ans =
     
128. 
     
129.     12
     
130. 
     
131. ----this should have smothing below
     
132. ----this should have smothing up
     
133. 
     
134. ans =
     
135. 
     
136.      8
     
137. 
     
138. 
     
139. ans =
     
140. 
     
141.    14.5000
     
142. 
     
143. 
     
144. ans =
     
145. 
     
146.     14
     
147. 
     
148. ----this should have smothing below
     
149. ----this should have smothing up
     
150. Parallel pool using the 'local' profile is shutting down.

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好吧.有学习了一点.下面是一个比较
01单CPU两层for,
02.多CPU两层for,先parfor 再for.
03.多CPU两层for ,先for 再parfor

如果求解的是一个对称matrix,则可以人尝试方法03.

1. clear all
   
2. clc
   
3. 
   
4. poolobj=parpool('local',4)
   
5. 
   
6. % parfor i=1:8
   
7. %     i
   
8. %     i*2-1.5
   
9. %     floor(i*2-1.5)
   
10. %     disp('----this should have smothing below ')
    
11. %     j=floor(i*2-1.5)
    
12. %     disp('----this should have smothing up')
    
13. %
    
14. % end
    
15. 
    
16. n=6
    
17. %% cpu version
    
18. tic
    
19. M1 = magic(n);
    
20. for x = 1:n
    
21.     for y = 1:n
    
22.         M2(x,y) = x*10 + y + M1(x,y)/10000;
    
23.     end
    
24. end
    
25. M2;
    
26. toc
    
27. 
    
28. %% multi cpu version 2 layer loop
    
29. % parfor out
    
30. tic
    
31. M3 = magic(n);
    
32. M4 = zeros(n);
    
33. parfor a = 1:n
    
34.     for b = 1:n
    
35.         M4(a,b) = a*10 + b + M3(a,b)/10000;
    
36.     end
    
37. end
    
38. M4;
    
39. toc
    
40. 
    
41. %% multi cpu version 2 layer loop
    
42. % for out
    
43. tic
    
44. M5 = magic(n);
    
45. M6 =zeros(n);
    
46. 
    
47. for a = 1:n
    
48.     parfor b = a:n
    
49.         M6(a,b) = a*10 + b + M5(a,b)/10000;
    
50.     end
    
51. end
    
52. M7=M6+M6';
    
53. toc
    
54. 
    
55. delete(poolobj)
    

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1. <blockquote>clear all

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