价值变量为每一个迭代

Question

这是我的代码：

Program Arrays_0 

Implicit none 

Integer :: i , Read_number , Vig_Position , Vipg_Position , n_iter 
Integer , parameter :: Br_gra = 12 
Integer , parameter , dimension (Br_gra) :: Vig = [ (i , i = 1 , Br_gra) ] 
Integer , parameter , dimension (Br_gra) :: Vipg = [ 0 , 1 , 1 , 1 , 2 , 2 , 3 , 4 , 4 , 7 , 7 , 7 ] 
Integer :: Result_of_calculation 

Write(*,*)"Enter the number (From 1 to Br_gra):" 
Read(*,*) Read_number 

Vig_Position = Vig(Read_number) 
Vipg_Position = Vipg(Vig_Position) 

    n_iter = 0 

    Result_of_calculation = Vig_Position 

    Do while(Vipg_Position .ne. Vipg(1)) 

     n_iter = n_iter + 1 

     Vig_Position = Vipg_Position 

     Result_of_calculation = Result_of_calculation + Vig_Position 

     Vipg_Position = Vipg(Vig_Position) 

    End Do 

Write(*,'(a,1x,i0)')"The number of iteration is:",n_iter 
Write(*,'(a,1x,i0)')"The result of calculation is:",Result_of_calculation 

End Program Arrays_0 

意向是在每次迭代中获取价值的变量： Vig_Position , Result_of_calculation and Vipg_position。 如何为这种计算声明变量？ 一般来说，有没有其他的方法来计算迭代次数？ 如何在迭代次数函数中声明变量为计算结果的编号？

Answer 1

现在已经澄清了这个问题，下面是在Fortran中解决问题的典型方法。这不是唯一可能的方式，但它是最一般的。常规调整策略以将旧尺寸加倍是合理的 - 您希望最小化调用次数。示例程序中设置的数据很小，因此为了显示我开始分配数组非常小的效果。实际上，你会想要一个相当大的初始分配（比如说至少100）。

请注意使用从其主机继承vals_t类型的内部过程。

Program Arrays_0 

Implicit none 

Integer :: i , Read_number , Vig_Position , Vipg_Position , n_iter 
Integer , parameter :: Br_gra = 12 
Integer , parameter , dimension (Br_gra) :: Vig = [ (i , i = 1 , Br_gra) ] 
Integer , parameter , dimension (Br_gra) :: Vipg = [ 0 , 1 , 1 , 1 , 2 , 2 , 3 , 4 , 4 , 7 , 7 , 7 ] 
Integer :: Result_of_calculation 

! Declare a type that will hold one iteration's values 
type vals_t 
    integer Vig_Position 
    integer Vipg_Position 
    integer Result_of_calculation 
end type vals_t 
! Declare an allocatable array to hold the values 
! Initial size doesn't matter, but should be close 
! to a lower limit of possible sizes 
type(vals_t), allocatable :: vals(:) 
allocate (vals(2)) 

Write(*,*)"Enter the number (From 1 to Br_gra):" 
Read(*,*) Read_number 

Vig_Position = Vig(Read_number) 
Vipg_Position = Vipg(Vig_Position) 

    n_iter = 0 

    Result_of_calculation = Vig_Position 

    Do while(Vipg_Position .ne. Vipg(1)) 

     n_iter = n_iter + 1 

     Vig_Position = Vipg_Position 

     Result_of_calculation = Result_of_calculation + Vig_Position 

     Vipg_Position = Vipg(Vig_Position) 

     ! Do we need to make vals bigger? 
     if (n_iter > size(vals)) call resize(vals) 
     vals(n_iter) = vals_t(Vig_Position,Vipg_Position,Result_of_calculation) 

    End Do 

Write(*,'(a,1x,i0)')"The number of iteration is:",n_iter 
Write(*,'(a,1x,i0)')"The result of calculation is:",Result_of_calculation 

! Now vals is an array of size(vals) of the sets of values 
! For demonstration, print the size of the array and the values 
Write(*,'(a,1x,i0)')"Size of vals is:", size(vals) 
Write(*,'(3i7)') vals(1:n_iter) 

    contains 
    ! Subroutine resize reallocates the array passed to it 
    ! with double the current size, copies the old data to 
    ! the new array, and transfers the allocation to the 
    ! input array 
    subroutine resize(old_array) 
    type(vals_t), allocatable, intent(inout) :: old_array(:) 
    type(vals_t), allocatable :: new_array(:) 

    ! Allocate a new array at double the size 
    allocate (new_array(2*size(old_array))) 
    write (*,*) "Allocated new array of size ", size(new_array) 

    ! Copy the data 
    new_array(1:size(old_array)) = old_array 

    ! Transfer the allocation to old_array 
    call MOVE_ALLOC (FROM=new_array, TO=old_array) 

    ! new_array is now deallocated 

    return 
    end subroutine resize 

End Program Arrays_0 

示例输出：

Enter the number (From 1 to Br_gra): 
12 
Allocated new array of size   4 
The number of iteration is: 3 
The result of calculation is: 23 
Size of vals is: 4 
     7  3  19 
     3  1  22 
     1  0  23