构建随机数组，搜索和排序 FORTRAN

Question

所以我已经构建了我的程序，但是我一遍又一遍地说同样的话：

benchmark.f90(17): error #6451: A dummy argument name is required in this context.   [N]
INTEGER, intent (in) :: N
------------------------^
benchmark.f90(18): error #6420: This array name is invalid in this context.   [A]
REAL, intent (out), DIMENSION (N), allocatable :: a
--------------------------------------------------^
benchmark.f90(18): error #6646: ALLOCATABLE or POINTER attribute dictates a deferred-shape-array   [A]
REAL, intent (out), DIMENSION (N), allocatable :: a
--------------------------------------------------^
benchmark.f90(17): error #6219: This variable, used in a specification expression, must be a dummy argument, a COMMON block object, or an object accessible through host or use association   [N]
INTEGER, intent (in) :: N
------------------------^
benchmark.f90(26): error #6219: This variable, used in a specification expression, must be a dummy argument, a COMMON block object, or an object accessible through host or use association   [N]
  REAL, INTENT(in out), DIMENSION(N) :: a
----------------------------------^
benchmark.f90(48): error #6420: This array name is invalid in this context.   [A]
    real, intent (in out), DIMENSION(N) ::  a
--------------------------------------------^
benchmark.f90(48): error #6219: This variable, used in a specification expression, must be a dummy argument, a COMMON block object, or an object accessible through host or use association   [N]
    real, intent (in out), DIMENSION(N) ::  a

所以我的数组和维度显然有问题，但由于我对可分配数组缺乏了解，我很难过。我已经包含了程序和子例程，希望有人可以轻松发现我的问题。

PROGRAM BENCHMARK
implicit none
integer :: N
REAL, Dimension(N), Allocatable :: a


write(6,*)'please enter size of array'
read(5,*) N
call randfunc(N,a)
call bubblesort(a,a)
call binarysearch(a,a)
deallocate (a)
END PROGRAM BENCHMARK

SUBROUTINE randfunc
implicit none

INTEGER, intent (in) :: N
REAL, intent (out), DIMENSION (N), allocatable :: a
   Allocate(a(1:N))
      CALL random_number(a)
      a = a*5.0
write(6,*)'this should be the randomly generated array',  a
END SUBROUTINE

SUBROUTINE bubblesort(a)
  REAL, INTENT(in out), DIMENSION(N) :: a
  REAL :: temp
  INTEGER :: i, j
  LOGICAL :: swapped = .TRUE.

  DO j = SIZE(a)-1, 1, -1
    swapped = .FALSE.
    DO i = 1, j
      IF (a(i) > a(i+1)) THEN
        temp = a(i)
        a(i) = a(i+1)
        a(i+1) = temp
        swapped = .TRUE.
      END IF
    END DO
    IF (.NOT. swapped) EXIT
  END DO
END SUBROUTINE


SUBROUTINE binarysearch

    REAL, intent (in out), DIMENSION(N) ::  a
    INTEGER :: ran, start, finish, mid
    INTEGER :: i, N, val
i = 1
    do i = 1, N
        READ(*,*) a(i)
    end do

    write(6,*) 'Enter Value'
    read(5,*) val

    start =  1
    finish = N
    ran = finish - start
    mid = (start + finish) /2

    do while( a(mid) /= val .and. ran >  0)
        if (val > a(mid)) then
           start = mid + 1
        else
           finish = mid - 1
        end if
           ran = finish - start
           mid = (start + finish)/2
    end do

    if( a(mid) /= val) then
      write(*,*) val, 'NOT FOUND'
    else
      write(*,*) 'VALUE AT' , mid
    end if
END SUBROUTINE

Answer 1

你有一些问题。

首先，您必须将一个虚拟参数传递给子例程。您没有将任何内容传递给子例程，并且通过声明 a 是 INTENT(in) 它正在寻找它。您对很多子例程（例如 randfunc）执行此操作。

你正在调用 randfunc

call randfunc(N,a)

但是你定义 randfunc 的方式不同。

subroutine randfunc

应该是什么时候

subroutine randfunc(N, a)
    integer, intent(in) :: N
    real, dimension(:), intent(out), allocatable :: a

二进制搜索也是如此

Subroutine binarySearch(a)
....
end Subroutine

接下来，可分配数组必须是延迟大小。你不能给他们一个 n 的大小，否则会违背分配它的目的。像这样：

real, dimension(:), allocatable :: a

另一个问题是您应该使用 CONTAINS 语句（或模块）将子例程放入主程序，因为如果您有一个带有延迟形状数组作为虚拟参数的函数，您必须有一个显式接口。

program benchmark
   stuff
    .....
 contains

  subroutine randfunct(N, a)
  end subroutine
  ! other subroutine declarations
  .....

 end program