Fortran 生成正态分布数据

christy

本例提供了用Fortran生成正态分布数据的代码和示范。完全符合Fortran语法，可直接使用。
本例使用了 Fortran90 提供的 random_seed 和 random_number 函数，用户无需手动再调用他们。

1. Module ran_mod
   
2.   Implicit None
   
3. ! ran return a uniform random number between 0-1  
   
4. ! norma return a normal distribution  
   
5. contains
   
6.   function ran()   !returns random number between 0 - 1  
   
7.     implicit none
   
8.     integer , save :: flag = 0
   
9.     double precision :: ran
   
10.     if(flag==0) then
    
11.       call random_seed()
    
12.       flag = 1
    
13.     endif
    
14.     call random_number(ran)     ! built in fortran 90 random number function  
    
15.   end function ran
    
16.   
    
17.   function normal(mean,sigma)
    
18.     implicit none
    
19.     integer :: flag
    
20.     double precision, parameter :: pi = 3.141592653589793239  
    
21.     double precision :: u1, u2, y1, y2, normal, mean, sigma
    
22.     save flag
    
23.     data flag /0/
    
24.     u1 = ran(); u2 = ran()
    
25.     if (flag.eq.0) then
    
26.       y1 = sqrt(-2.0d0*log(u1))*cos(2.0d0*pi*u2)
    
27.       normal = mean + sigma*y1
    
28.       flag = 1
    
29.     else
    
30.       y2 = sqrt(-2.0d0*log(u1))*sin(2.0d0*pi*u2)
    
31.       normal = mean + sigma*y2
    
32.       flag = 0
    
33.     endif  
    
34.   end function normal
    
35. !The above codes are made in Fortran 90 language, if you have any question, you may write to sealin2008@hotmail.com
    
36. End Module ran_mod
    
37. 
    
38. Program www_fcode_cn
    
39.   use ran_mod
    
40.   Implicit None
    
41.   Integer , parameter :: N = 10000
    
42.   Real( Kind = 8 ) :: a( N )
    
43.   integer :: i
    
44.   Open( 12 , File = 'out.txt' )
    
45.   Do i = 1 , N
    
46.     a( i ) = normal( 5.0D0 , 2.0D0 )
    
47.     write( 12 , * ) a(i)
    
48.   End Do
    
49.   Close( 12 )
    
50. End Program www_fcode_cn

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