Topic: Use of TYPE arrays in General

Paul,

Following on from the question I asked previously, the following example appears to show that the compiler generates a temporary array, when providing part of a Type data set. Presumably the temporary array is on the stack ? With large type data sets, could this lead to stack overflow problems ? Or have I mis-understood my example ?

!     Last change:  JDC  18 Sep 2009    9:03 am
module my_data
integer*4, parameter :: mxnode = 10

TYPE Coordinate_Record 
   real*8 X 
   real*8 Y 
   real*8 Z 
   integer*4 fixity(6) 
END TYPE Coordinate_Record 

type (Coordinate_record) nodes(mxnode)

end module

use my_data
integer*4 index(mxnode), i

do i = 1,mxnode
   call random_number (nodes(i)%x)
   call random_number (nodes(i)%y)
   call random_number (nodes(i)%z)
end do

call dsort@ (index, nodes%z, mxnode)  ! this works

do i = 1,mxnode
   write (*,'(2i5,3f10.6)') i, index(i), nodes(index(i))%x, nodes(index(i))%y, nodes(index(i))%z
end do

call test_argument_1 (nodes%z, mxnode)   ! change is lost
write (*,1000) 'type',nodes(10)%z, ' change to nodes(i)%z lost'

call test_argument_2 (nodes%z, mxnode)   ! change is updated
write (*,1000) 'type',nodes(10)%z, ' change to nodes_z(i) updated'

1000 format (a,f10.6,a)

end

subroutine test_argument_1 (nodes_z, num)

use my_data

real*8 nodes_z(num)
integer*4 num, i

   i = 10
   write (*,1000) 'type',nodes(i)%z, ': Argument',nodes_z(i)
   nodes(i)%z = i
   write (*,1000) 'type',nodes(i)%z, ': Argument',nodes_z(i)
   return
1000 format (2(a,f10.6))
end

subroutine test_argument_2 (nodes_z, num)

use my_data

real*8 nodes_z(num)
integer*4 num, i

   i = 10
   write (*,1000) 'type',nodes(i)%z, ': Argument',nodes_z(i)
   nodes_z(i) = i
   write (*,1000) 'type',nodes(i)%z, ': Argument',nodes_z(i)
   return
1000 format (2(a,f10.6))
end