Fortran中的数组与动态数组

原创已于 2023-07-06 21:14:50 修改 · 1.3k 阅读

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#fortran

于 2023-07-06 01:35:30 首次发布

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Fortran中的数组与动态数组

数组与动态数组示例

program array_exam
  implicit none

  integer, parameter :: n = 5
  integer :: i

  integer :: static_array(n) = [1,2,3,4,5]

  integer, allocatable :: dynamic_array(:)

  allocate(dynamic_array(n))

  dynamic_array = [(i * 2, i = 1, n)]

  print *, "Static Array:"
  do i = 1, n
    print *, static_array(i)
  end do
  
  print *, "Dynamic Array:"
  do i = 1, n
    print *, dynamic_array(i)
  end do
  
  deallocate(dynamic_array)
  
  write(*,*) "Program over!"
  read(*,*)

end program array_exam

动态数组的优势

处理不定长数据

利用动态数组从不定长文件中读取数据
事实上，在实际工作中，我们往往需要注意到一个问题
- 你怎么可能不知道要处理的数据的长度呢？
  - 当然，傻瓜x方可能不懂规范
  - 也有可能有二傻子在文件中添加没有意义的注释啥的
- 只需要将文件大小除一下字节长度即可

program data_storage
  implicit none

  integer :: n, i
  real, allocatable :: data(:)
  real, allocatable :: newdata(:)

  open(unit=10, file='data.txt', status='old', action='read')

  n = 1
  allocate(data(1))

  do
    read(10, *, iostat=i) data(n)
    if ((i /= 0) .and. (i /= -1)) then
      write(*,*)"here is:",n
      write(*,*)"fail because iostat is:",i
      exit
    end if 

    
    if (i /= -1) then
      n = n + 1      
      allocate(newdata(n),stat=i)
      newdata(1:n-1) = data(1:n-1)
      deallocate(data)
      allocate(data(n), stat=i)
      data(1:n-1) = newdata(1:n-1)
      deallocate(newdata)
    else 
      write(*,*)"read over!"
      n = n - 1
      allocate(newdata(n),stat=i)
      newdata(1:n) = data(1:n)
      deallocate(data)
      allocate(data(n), stat=i)
      data(1:n) = newdata(1:n)
      deallocate(newdata)      
      exit 
    end if 

  end do

  close(10)

  print *, "Array size:", n
  print *, "Array elements:"
  do i = 1, n
    print *, data(i)
  end do

  deallocate(data)
  write(*,*)"press any key to exit !"
  read(*,*)
end program data_storage

fortran90 中有一个小问题，他必须读了之后才能知道具体有没有达到文章的末尾，所以会有一串if i == -1 的问题

数据文件结构：

数组与多维数组

数组的声明
- 类型说明符数组名（[维数下界（默认为1）:]维数上界）
- 类型说明符，维度（[维数下界（默认为1）:]维数上界）:: 数组名
数组的引用
- 下标为6的元素：a(6)
- 数组名（【起始下标】：【终止下标】【：步长】）：a(1:10:3)
数组的赋值语句
- a(i) = i
- a(5) = (/1,2,3,4,5/)
  - 限制 fortran90 以后
- data 赋值方法

数组中元素的存储顺序与data赋值方法

[m,n]:n行m列
Fortran 中的存储顺序十分的甚至可以说九分的复杂，他是基于一种神秘的考虑逻辑的，简单的说
- 我们在数字电路中学习过最小项的概念，
  - fortran的存储顺序是与最小项这一个概念类似的。
    - 如 A0 A1 A2 A3...
    - 对应的是 (A0,A1,A2,A3) 的数组

data 赋值方法

普通赋值
- 这里的 and 符号表示分行写代码

program data_example

  implicit none
  real :: a(5)
  integer i 


  data a / 1.0,&
           2.0,&
           3.0,&
           4.0,&
           5.0 /
           
  write(*,*) "Array:"
  do i = 1, 5
    write(*,*) a(i)
  end do

  read(*,*)
end program data_example

多维数组

program data_example

  implicit none
  real :: b(2,3)
  integer i,j

  data b /1.0, 2.0, 3.0 ,4.0, 5.0, 6.0 /
  
  write(*,*) "Array :"

  do i = 1,2
    do j = 1,3
      write(*,*) b(i,j)
    end do
  end do

  read(*,*)
end program data_example

数组函数

maxval() and minval()

program function_example
  implicit none
  integer i

  real :: f(3, 4)
  real :: max_value = 0
  real :: min_value = 0 

  f = reshape([(i, i=1, size(f))], [3,4])  
  write(*,*)"array f:"
  write(*,*)f 

  max_value = maxval(f(:,2))  
  print *, "Max value of array f:", max_value

  min_value = minval(f(3,:))  
  print *, "Min value of array f:", min_value
  
  write(*,*)"press any key to exit"
  read(*,*)
end program function_example

maxloc() and minloc()

注意，这两个函数返回的是一个只包含一个元素的一维数组

program array
implicit none

   real,dimension(1:6) :: a = (/ 21.0, 12.0,33.0, 24.0,15.0, 16.0/)
   real,dimension(2,3) :: b
   integer max_a(1)
   integer min_a(1)

   b = reshape(a,[2,3])
   write(*,*) "max of a"
   max_a = maxloc(a)
   write(*,*) max_a
   write(*,*) "min of a"
   min_a = minloc(a)
   write(*,*) min_a    
   read(*,*)
end program array

sum() and product()

求和和求乘积

program sum_function_example
  implicit none

  integer :: h(4)
  real :: total_sum
  real :: total_pro

  h = [3, 6, 9, 12]  
  total_sum = sum(h)  
  total_pro = product(h)
  write(*,*)"Total sum of array h:", total_sum
  write(*,*)"Total pro of array h:", total_pro

  write(*,*) "press any key to exit"
  read(*,*)
end program sum_function_example

count()

program count_function_example
  implicit none

  integer :: k(6)
  integer :: num
  k = [1, 10, 1, -10, 1, 1]  
  num = count(k==1)  
  print *, "Number of 1 in array:", num
  num = count(k.gt.1)  
  print *, "Number bigger than 1 in array:", num  
    num = count(k.le.1)  
  print *, "Number smaller than or equal 1 in array:", num
  read(*,*)
end program count_function_example

all() and any()

program all_function_example
  implicit none

  logical :: l(3)
  logical :: resultl
  logical :: m(4)
  logical :: resultm

  l = [.true., .false., .true.] 
  resultl = all(l) 
  write(*,*) "All elements in array are true:", resultl

  m = [.false., .true., .false., .false.] 
  resultm = any(m) 
  write(*,*) "At least one element in array is true:", resultm

  read(*,*)
end program all_function_example

transpose(array)

矩阵转置

program function_example
  implicit none

  integer i,j
  integer :: n(2,3)
  integer :: transposed(3,2)

  n = reshape([1,2,3,4,5,6],[2,3])  
  transposed = transpose(n)  

  print *, "Original matrix:"
  do i = 1,size(n(:,1))
    do j = 1,size(n(1,:))
      print *, n(i,j)
    end do
  end do

  print *, "Transposed matrix:"
  do i = 1,size(transposed(:,1))
    do j = 1,size(transposed(1,:))
      print *, transposed(i,j)
    end do
  end do

  read(*,*)
end program function_example

shape(array)

program function_example

  implicit none

  integer :: a(3,4,5)
  integer :: dimension(3)
  dimension = shape(a)

  write(*,*) "Array dimension:", dimension
  read(*,*)

end program function_example

size()

所有维度上的元素总数

program function_example

  implicit none
  real :: b(1,2,3)
  integer :: total_size,second_dimension_size

  total_size = size(b)  
  second_dimension_size = size(b, dim=2) 

  write(*,*) "Total size of array b:", total_size
  write(*,*) "Size of second dimension:", second_dimension_size
  read(*,*)

end program function_example

lbound() and ubound()

返回给定数组在指定维度上的最低(高)索引

program function_example

  implicit none

  real :: c(-4:5,10)
  integer :: starting_index, ending_index


  starting_index = lbound(c,dim=1)  
  ending_index = ubound(c, dim=2)  

  print *, "Starting index of first dimension:", starting_index
  print *, "Ending index of second dimension:", ending_index

  read(*,*)

end program function_example

reshape(source_array, shape)

一定要记得提前分配内存，任何时候都要记得这件事情
- 具体操作参见上面的操作代码，有相关reshape函数的使用

流传很广的一些计算机笑话

Why programmers always mix up Halloween and Christmas?
- Because Oct 31 == Dec 25!
There are 10 types of people in the world: Those who understand binary, those who don't

Good Luck!

To my best friend for my rest life.