build random array, search and sort FORTRAN

问题:

So I've built my program but I'm getting errors saying the same stuff over and over:

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 

so it obviously has a problem with my array and dimensions, but due to my lack of understanding regarding allocatable arrays I'm stumped. I've included the program and subroutines in the hope that someone can spot my problem easily.

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 

回答1:

You have a few problems.

First you must pass a dummy argument to the subroutine. You are not passing anything to the subroutine and by declaring that a is INTENT(in) it is looking for that. You do this for a lot of the subroutines such as randfunc.

You are calling randfunc

call randfunc(N,a) 

But the way you define randfunc is different.

subroutine randfunc 

When it should be like

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

Same goes with binarySearch

Subroutine binarySearch(a) .... end Subroutine 

Next, allocatable arrays must be deferred size. You can't give them a size of n otherwise that defeats the purpose of allocating it. Like so:

real, dimension(:), allocatable :: a 

Another problem is that you should put the subroutines into the main program with a CONTAINS statement(or module) because if you have a function with a deferred shape array as a dummy argument you must have an explicit interface.

program benchmark    stuff     .....  contains    subroutine randfunct(N, a)   end subroutine   ! other subroutine declarations   .....   end program 

文章来源: build random array, search and sort FORTRAN