nvfortran -acc: derived-type variable without a data clause is not copied back from a serial region

Legality: independently confirmed. 2 independent readings find the program legal and the result required. How this is checked

Affected variants

Compiler	MI300A gfx942 unified memory (XNACK 1)	MI300A gfx942 copy (XNACK 0)	MI250X gfx90a copy (XNACK 0)	MI300X gfx942 copy (XNACK 0)	MI350X gfx950 copy (XNACK 0)	A100 sm_80 separate memory	A100 sm_80 managed memory
AFAR 24.3.0	n/a	n/a	n/a	n/a	n/a	n/a	n/a
CCE 19.0.0	correct	correct	unknown not run	unknown not run	unknown not run	n/a	n/a
CCE 20.0.2	correct	correct	unknown not run	unknown not run	unknown not run	n/a	n/a
CCE 21.0.3	correct	correct	unknown not run	unknown not run	unknown not run	n/a	n/a
CCE 21.0.4	correct	correct	unknown not run	unknown not run	unknown not run	n/a	n/a
NVHPC 25.11	n/a	n/a	n/a	n/a	n/a	behaves incorrectly	behaves incorrectly
NVHPC 26.9	n/a	n/a	n/a	n/a	n/a	behaves incorrectly	behaves incorrectly
GCC 16.2.0	correct	correct	correct	correct	correct	correct	n/a

"behaves incorrectly" / "not supported": this issue, confirmed in up to four environments (another build directory, another node, a repeat). "fails another way": a different failure, not counted as this issue. "unknown": not run there, or the runs disagree.

Messages

Result	Compiler and GPU	Message
behaves incorrectly	NVHPC 25.11, A100 separate NVHPC 25.11, A100 managed NVHPC 26.9, A100 separate NVHPC 26.9, A100 managed	show c1= 101

Reproduce

NVHPC 25.11, A100 separate

export LD_LIBRARY_PATH=$NVHPC_25_11/compilers/lib
nvfortran -acc=gpu -gpu=cc80 -gpu=mem:separate -O2 repro.f90 -o repro
./repro

NVHPC 26.9, A100 separate

export LD_LIBRARY_PATH=$NVHPC_26_9/compilers/lib
nvfortran -acc=gpu -gpu=cc80 -gpu=mem:separate -O2 repro.f90 -o repro
./repro

CCE 19.0.0, MI300A unified (runs correctly)

module load cce/19.0.0 craype-accel-amd-gfx942 rocm/6.4.3
module unload cray-mpich
ftn -h acc -O2 repro.f90 -o repro
HSA_XNACK=1 ./repro

Program (29 lines)

! # Finding: NVHPC OpenACC does not copy back a derived-type variable
! # written through a component in a serial construct
!
! - compilers: NVHPC nvfortran 25.11 and 26.9, A100 (sm_80), -acc=gpu -gpu=cc80, separate and
!   managed memory, -O2
! - expected: c1= 203. xc has an exposed access in the serial construct and no visible data clause;
!   in that case "An aggregate variable will be treated as if it appears either: ... In a copy
!   clause otherwise" (OpenACC 3.4 §2.6.2 p.41 l.1388-1391). The access to xc%c1 is an access to xc (§2.6.2 l.1374), and a
!   derived type is a composite type, hence an aggregate (glossary p.159 l.5792-5796, 5807-5811)
! - actual: c1= 101 on both releases and both memory modes
! - control (same compiler): serial copy(xc) (data/reports/fuzz-stress-audit/r5-acc-component-control.f90):
!   203 on both releases and modes
! - other families: CCE 19/20/21 (ftn -h acc) give 203 on this program (MI300A HSA_XNACK 1 and 0, MI250X)
! - legality: legal by reading: serial runs one gang, one worker, one vector lane; xc is a local
!   variable of the main program
! - evidence: results/stress/audit/runs-nvhpc.jsonl. The confirmer gave needs_human (R22, no
!   cross-machine witness); the audit counts the MI300A results
program acc_component
  implicit none
  type :: t
    integer(8) :: c1
  end type t
  type(t) :: xc
  xc%c1 = 101
  !$acc serial
    xc%c1 = 2 * xc%c1 + 1
  !$acc end serial
  print '(a,i0)', 'c1= ', xc%c1
end program acc_component

Source in the repository

Something to add? Dispute its legality · Report it fixed in a newer release · Report a mistake on this page

Expected and observed

Expected

c1= 203

Observed where it behaves incorrectly

c1= 101

What the specification requires

The specification text this program relies on and the compiler is expected to support.

OpenACC 3.4 §2.6.2 p.41 l.1388-1391

An aggregate variable will be treated as if it appears either: ... In a copy clause otherwise

OpenACC 3.4 §2.6.2

Evidence

Same compiler, one change

serial copy(xc): CCE 19.0.0: correct; CCE 20.0.2: correct; CCE 21.0.3: correct; CCE 21.0.4: correct; NVHPC 25.11: correct; NVHPC 26.9: correct

Control program

program acc_component
  implicit none
  type :: t
    integer(8) :: c1
  end type t
  type(t) :: xc
  xc%c1 = 101
  !$acc serial copy(xc)
    xc%c1 = 2 * xc%c1 + 1
  !$acc end serial
  print '(a,i0)', 'c1= ', xc%c1
end program acc_component

Other compilers run it correctly

CCE 19.0.0, CCE 20.0.2, CCE 21.0.3, CCE 21.0.4, GCC 16.2.0