Observed issues › fuzz/b1-183-afar
amdflang at HSA_XNACK=1: a parallel region with a reduction (or atomic) nested in a distribute loop of a reducing teams region aborts
Legality: not independently confirmed. no independent review yet How this is checked
Same issue as fuzz/916-afar; this program is another reproducer of it.
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 | behaves incorrectly | correct | unknown not run | correct | correct | 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 | correct | correct |
| NVHPC 26.9 | n/a | n/a | n/a | n/a | n/a | correct | correct |
| 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 | AFAR 24.3.0, MI300A unified | showRESULT checksum=1118127074 |
Reproduce
AFAR 24.3.0, MI300A unified
$AFAR/bin/amdflang -fopenmp --offload-arch=gfx942 -O2 repro.f90 -o repro HSA_XNACK=1 OMP_TARGET_OFFLOAD=mandatory ./repro
CCE 19.0.0, MI300A unified (runs correctly)
module load cce/19.0.0 craype-accel-amd-gfx942 rocm/6.4.3 module unload cray-mpich ftn -fopenmp -O2 repro.f90 -o repro HSA_XNACK=1 OMP_TARGET_OFFLOAD=mandatory ./repro
Program (50 lines)
! Minimized by compliance.fuzz_min from fuzz seed 183 (fuzz-3).
! toolchain: afar (-O2, HSA_XNACK=1, OMP_TARGET_OFFLOAD=mandatory)
! failure: wrong_code
! expected: the host reference checksum (host reference (cce19/elision) checksum=1123737439)
! observed: device checksum=1118127074 ran_on_host=0
! Legal OpenMP 5.2: offload.engine.rules accepts it (offload.engine.prerun.check, rerun: with the
! race rule and the restriction checks); nvfortran/nvc 26.9 and 25.11 (NVHPC, not under test
! here) compile it; the check's other witness, the AFAR flang front end, is the compiler under
! test and is not counted; no gfortran or gcc is a legality witness.
module fuzz_mod
implicit none
contains
end module fuzz_mod
program fuzz_prog
use omp_lib, only: omp_is_initial_device
implicit none
integer, parameter :: n = 24, m = 2
integer :: ic(n, m)
integer, allocatable :: o1(:, :)
integer :: i, j, r1a
integer(8) :: cs
allocate(o1(n, m))
do j = 1, m
do i = 1, n
ic(i, j) = mod((i + 1 * j) * 20 + 50, 30011) - 2834
end do
end do
o1 = 0
r1a = 7
! fuzz: kernels
!$omp target teams distribute map(tofrom: r1a)
do i = 1, n
!$omp parallel do
do j = 1, m
o1(i, j) = iand(ic(i, (mod(((j * 3) + 1), m) + 1)), 255)
!$omp atomic
r1a = min(r1a, mod(i, n))
end do
end do
!$omp end target teams distribute
! fuzz: checksum
cs = 0
cs = modulo(cs * 31_8 + int(r1a, 8), 2147483629_8)
do j = 1, m
do i = 1, n
cs = modulo(cs * 31_8 + int(o1(i, j), 8), 2147483629_8)
end do
end do
print '(a,i0,a,i0)', 'RESULT checksum=', cs, ' ran_on_host=', 0
end program fuzz_prog
Something to add? Dispute its legality · Report it fixed in a newer release · Report a mistake on this page
Expected and observed
Observed where it behaves incorrectly
RESULT checksum=1118127074
What the specification requires
The specification text this program relies on and the compiler is expected to support.
The same requirement as the issue fuzz/916-afar.
OpenMP 5.2 §5.5.8 p.135 l.4-10
For the teams construct, one or more private copies of each list item are created for the initial task of each team in the league, as if the private clause had been used. For the loop construct, private copies are created and used in the construct according to the description and restrictions in Section 5.3. At the end of a region that corresponds to a construct for which the reduction clause was specified, the original list item is updated by combining its original value with the final value of each of the private copies, using the combiner of the specified reduction-identifier.
OpenMP 5.2 §5.5.8 p.135 l.26-27
A list item that appears in a reduction clause on a worksharing construct must be shared in the parallel region to which a corresponding worksharing region binds.
Evidence
Other compilers run it correctly
CCE 19.0.0, CCE 20.0.2, CCE 21.0.3, CCE 21.0.4, NVHPC 25.11, NVHPC 26.9, GCC 16.2.0