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I'm getting the famous warning of a temporary array created, forrtl: warning (406): fort: (1): In call to XXXX, an array temporary was created for argument #N. However, I create simple code to mimic the larger code, and I don't get the same warning. See code below. Essentially I'm passing in a subset array into subroutine XXXX, and indexing on the last index, which should give me a contiguous memory chunk. What else could cause this temporary array creation? ifort version 16.0.0
Code:
program testArrayPassSubroutine integer :: sze,i real, dimension(3,3,2) :: arr real, dimension(2,3,3) :: arr2 !do k=1,2 ! do j=1,3 ! do i=1,3 ! arr(i,j,k) = (k-1)*9 + (j-1)*3 + i ! enddo ! enddo !enddo !do k=1,3 ! do j=1,3 ! do i=1,2 ! arr2(i,j,k) = (k-1)*9 + (j-1)*3 + i ! enddo ! enddo !enddo !This is like the original code, which throws the warning(406):...temporary array creation write(*,*) "Test1 start" call test(arr(:,:,1)) write(*,*) "Test1 done" !This is where I would expect a warning(406), and indeed see it write(*,*) "Test2 start" call test(arr2(1,:,:)) write(*,*) "Test2 done" contains subroutine test(a) integer :: i,j real, dimension(3,3) :: a do i=1,3 do j=1,3 a(j,i) = j*i enddo enddo write(*,*) "Array",(a) write(*,*) "" end subroutine test end program testArrayPassSubroutine
Output:
Test1 start
Array 1.000000 2.000000 3.000000 2.000000
4.000000 6.000000 3.000000 6.000000 9.000000
Test1 done
Test2 start
forrtl: warning (406): fort: (1): In call to TEST, an array temporary was created for argument #1
Image PC Routine Line Source
a.out 0000000000403876 Unknown Unknown Unknown
a.out 0000000000400689 MAIN__ 29 testArrayPassSubroutine.F90
a.out 00000000004004AE Unknown Unknown Unknown
a.out 000000000048D9F1 Unknown Unknown Unknown
a.out 0000000000400389 Unknown Unknown Unknown
Array 1.000000 2.000000 3.000000 2.000000
4.000000 6.000000 3.000000 6.000000 9.000000
Test2 done
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Your output shows no array temporary in Test1 (expected result). Section arr(:,:,1) is contiguous
And shows array temporary in Test 2 (expected result). Section arr2(1,:,:) is not contiguous.
Jim Dempsey
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Yes, that's the point, perhaps my code comments weren't clear. This code is derived from a larger code. The larger code effectively does Test1, which as this smaller code shows should not create array temporarys. But for some reason in the larger code I am getting an array temporary. Is there another reason array temporary's would be created?
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Generally, if the thing you're passing is not contiguous and the called routine expects contiguity, a copy will be made. My guess is that you are not correctly representing what the "larger code" does. I do know that there are some cases where the compiler doesn't even check and always makes a copy. The cases I have seen are where the index expressions include derived-type components, and should be improved in future versions.
Please show us the actual call line that makes the copy.
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OK, here is a snippet of the larger code, I've tried to reduce it to the call and variables being passed in, hopefully this is clear enough. The warning is on the call col_f_f_df in the main subroutine.
There is a derived-type object (ci) being passed in, and in the subroutine indexed and input into the array being complained about (fi_half, through delr). Could this be the reason?
subroutine main() ... real (kind=8), dimension(col_f_nvr, col_f_nvz) :: dist_ni,dfi, dist_iteri ! local real (kind=8),dimension((col_f_nvr-1),(col_f_nvz-1),2) :: fi_half,dfidr,dfidz,fe_half,dfedr,dfedz ... type(col_f_core_type) :: ci, ce ... do iter_inter=1, vpic_inner_iter_max ... call col_f_f_df(ci, 1, dist_iteri, fi_half(:,:,1), dfidr(:,:,1), dfidz(:,:,1)) !i-i ... enddo subroutine col_f_f_df(cs, op_mode, f, f_half, dfdr, dfdz) ... type(col_f_core_type), intent(in) :: cs integer, intent(in) :: op_mode real(kind=8) :: mesh_dr, mesh_dz real(kind=8), dimension(col_f_nvr, col_f_nvz) :: f real(kind=8), dimension(col_f_nvr-1, col_f_nvz-1) :: f_half, dfdr, dfdz real(kind=8) :: tmpr1, tmpr2, tmpr3, tmpr4 integer :: index_I, index_J real (kind=8) :: delr, cdelr, delz, cdelz do index_I=1,col_f_nvz-1 do index_J=1, col_f_nvr-1 delr = cs%delta_r(index_J,op_mode) cdelr = 1D0-delr delz = cs%delta_z(index_I,op_mode) cdelz = 1D0-delz tmpr1 = f(index_J, index_I) tmpr2 = f(index_J+1, index_I) tmpr3 = f(index_J,index_I+1) tmpr4 = f(index_J+1,index_I+1) f_half(index_J, index_I) = tmpr1 * delr*delz & + tmpr3 * delr*cdelz & + tmpr2 * cdelr*delz & + tmpr4 * cdelr*cdelz ... enddo enddo
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What is the message that comes out - which argument does it complain about? How you fill in the arrays is of no consequence.
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It's the fourth argument, fi_half:
forrtl: warning (406): fort: (1): In call to COL_F_F_DF, an array temporary was created for argument #4
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Sorry, its the fourth, fifth, and sixth (I'm using MPI, so several warning show up, esp. since this is in a loop):
forrtl: warning (406): fort: (1): In call to COL_F_F_DF, an array temporary was created for argument #4
forrtl: warning (406): fort: (1): In call to COL_F_F_DF, an array temporary was created for argument #5
forrtl: warning (406): fort: (1): In call to COL_F_F_DF, an array temporary was created for argument #6
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How and where are col_f_nvr and col_f_nvz declared? I haven't been able yet to construct a test case that reproduces the problem.
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Michael C. wrote:
Sorry, its the fourth, fifth, and sixth (I'm using MPI, so several warning show up, esp. since this is in a loop):
forrtl: warning (406): fort: (1): In call to COL_F_F_DF, an array temporary was created for argument #4
forrtl: warning (406): fort: (1): In call to COL_F_F_DF, an array temporary was created for argument #5
forrtl: warning (406): fort: (1): In call to COL_F_F_DF, an array temporary was created for argument #6
Looking at your code snippet in Message #5, it seems as though you might be doing something along the lines in the code shown below. In such cases, as explained by Jim and Steve, the compiler might suspect the array section is not contiguous and add code to create an array temporary. As Steve indicated, you need to supply a proper reproducer or share actual code with Intel to get good advice.
program p implicit none integer, parameter :: M = 3 integer :: N real :: r(M,M,2) N = M-1 call foo( r(1:N,1:N,:) ) print *, " r = ", r stop contains subroutine foo( r ) real, intent(inout) :: r(N,N,2) !.. N is some host-associated variable integer :: i do i = 1, size(r, dim=3) call bar( r(:,:,i) ) end do return end subroutine foo subroutine bar( s ) real, intent(inout) :: s(N,N) !.. N is some host-associated variable s = 0.0 return end subroutine bar end program
Upon execution on Windows,
forrtl: warning (406): fort: (1): In call to FOO, an array temporary was created for argument #1 Image PC Routine Line Source p64.exe 000000013FE152DE Unknown Unknown Unknown p64.exe 000000013FE11197 MAIN__ 12 p.f90 p64.exe 000000013FEAD77E Unknown Unknown Unknown p64.exe 000000013FEAE0AC Unknown Unknown Unknown p64.exe 000000013FEAE1EE Unknown Unknown Unknown kernel32.dll 0000000076F859DD Unknown Unknown Unknown ntdll.dll 00000000771BA631 Unknown Unknown Unknown r = 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 Press any key to continue . . .
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The problem is that a subscript of (:,:,1) is always contiguous for an array that started out as contiguous, which, if the declaration shown is representative, is the case. I would very much like to see an actual test case, as I suspect there is something important that hasn't been shown.
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In your #10 example, N is not the full size of the first two dimensions of r.
You requested to transmit r(1:M-1,1:M-1,i) i=1,2
Where M is the size of the first two dimensions of r. This section is not contiguous because
sections r(M,1:M,i) and r(1:M,M,i) (last row and last column) are not passed (thus must be effectively compressed out via temporary).
If you want to avoid the array temporary, pass the entire array section (1:M,1:M,i) to foo. Perform similar fix to bar.
Jim Dempsey
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#10 is FortranFan's. He's trying to help, but his example isn't representative of Michael C's code as shown in this thread.
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jimdempseyatthecove wrote:
In your #10 example, N is not the full size of the first two dimensions of r. ..
Steve Lionel (Intel) wrote:
#10 is FortranFan's. He's trying to help, but his example isn't representative of Michael C's code as shown in this thread.
Yes, as mentioned by Steve, I was simply trying to suggest to OP that information on array dimensions (col_f_nvr, col_f_nvz) and how they are defined need to be provided as they do play a role, as shown by the simple code in Message #10.
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Steve Lionel (Intel) wrote:
How and where are col_f_nvr and col_f_nvz declared? I haven't been able yet to construct a test case that reproduces the problem.
There is a module read in at the beginning of the subroutine I called "main":
subroutine main() use col_f_module
In col_f_module are defined col_f_nvr and col_f_nvz:
integer :: col_f_nvr, col_f_nvz
And they are instantiated in a setup routine called prior to this "main" subroutine (sorry, shouldn't have used "main" for the subroutine name). Values are derived from an input file; for the simulation I'm running they are:
col_f_nvr = 32 col_f_nvz = 31
After the initial setup, these never change, so I don't think it should be an issue pointed out in #10.
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Michael C. wrote:
.. In col_f_module are defined col_f_nvr and col_f_nvz: .. After the initial setup, these never change, so I don't think it should be an issue pointed out in #10.
I think your situation is akin to:
program p implicit none integer :: N N = 3 call foo() stop contains subroutine foo( ) real :: r((N-1),(N-1),2) call bar( r(:,:,1) ) return end subroutine foo subroutine bar( s ) real, intent(inout) :: s(N-1,N-1) s = 0.0 return end subroutine bar end program
Upon execution on Windows,
forrtl: warning (406): fort: (1): In call to BAR, an array temporary was created for argument #1 Image PC Routine Line Source p64.exe 000000013FAF827E Unknown Unknown Unknown p64.exe 000000013FAF128C P_ip_FOO 19 p.f90 p64.exe 000000013FAF1040 MAIN__ 9 p.f90 p64.exe 000000013FB84C7E Unknown Unknown Unknown p64.exe 000000013FB855AC Unknown Unknown Unknown p64.exe 000000013FB856EE Unknown Unknown Unknown kernel32.dll 0000000076F859DD Unknown Unknown Unknown ntdll.dll 00000000771BA631 Unknown Unknown Unknown Press any key to continue . . .
Note if one makes a small change to code as shown below, no run-time warning about array temporary is issued:
program p implicit none integer :: N integer :: M N = 3 M = N-1 call foo() stop contains subroutine foo( ) real :: r(M,M,2) call bar( r(:,:,1) ) return end subroutine foo subroutine bar( s ) real, intent(inout) :: s(M,M) s = 0.0 return end subroutine bar end program
I think I have noticed this before. I'll leave it up to you and Intel to follow-up.
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Or you can consider the following:
module m implicit none integer :: N end module m subroutine foo( ) use m, only : N real :: r((N-1),(N-1),2) call bar( r(:,:,1) ) return end subroutine foo subroutine bar( s ) use m, only : N real, intent(inout) :: s(N-1,N-1) s = 0.0 return end subroutine bar
program p use m, only : N implicit none N = 3 call foo() stop end program
Upon execution,
forrtl: warning (406): fort: (1): In call to BAR, an array temporary was created for argument #1 Image PC Routine Line Source p64.exe 000000013F78427E Unknown Unknown Unknown p64.exe 000000013F781325 FOO 15 m.f90 p64.exe 000000013F78198C MAIN__ 9 p.f90 p64.exe 000000013F814C3E Unknown Unknown Unknown p64.exe 000000013F81556C Unknown Unknown Unknown p64.exe 000000013F8156AE Unknown Unknown Unknown kernel32.dll 0000000076F859DD Unknown Unknown Unknown ntdll.dll 00000000771BA631 Unknown Unknown Unknown Press any key to continue . . .
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Michael C. wrote:
..
subroutine main() ... real (kind=8), dimension(col_f_nvr, col_f_nvz) :: dist_ni,dfi, dist_iteri ! local real (kind=8),dimension((col_f_nvr-1),(col_f_nvz-1),2) :: fi_half,dfidr,dfidz,fe_half,dfedr,dfedz ... ..
Try removing the parenthesis around col_f_nvr-1 and col_f_nvz-1 in your actual code!
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Thanks to FortranFan for coming up with a complete reproducer. I have escalated this as issue DPD200380709. Indeed, the parentheses in the declaration trigger the problem - apparently the compiler decides that the declaration is "too complex" to do the run-time test, even though the subscript syntax in the call should indicate that the argument will always be contiguous.
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Yes, thanks FortranFan, removing the parenthesis removed the array temporary warning. Thanks to all for looking into this.
Just to be sure, this was just a bug in the warning system from the compiler right? There weren't actually array temporarys being created, correct?
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No, there were copies being made.The compiler thought it was too complex to generate the checking code, so it made the copy unconditionally, when without the parentheses it realized it didn't need to check as a copy would never be needed.
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