Hello,
The following code example compiled with `mpiifort` produces a segfault error:
module test_intel_mpi_mod
implicit none
integer, parameter :: dp = kind(1.0d0)
type :: Container
complex(kind=dp), allocatable :: arr(:, :, :)
end type
contains
subroutine test_intel_mpi()
use mpi_f08, only: &
MPI_Init_thread, &
MPI_THREAD_SINGLE, &
MPI_Finalize, &
MPI_Comm_rank, &
MPI_COMM_WORLD, &
MPI_COMPLEX16, &
MPI_Bcast
integer :: provided
integer :: rank
type(Container) :: cont
call MPI_Init_thread(MPI_THREAD_SINGLE, provided)
call MPI_Comm_rank(MPI_COMM_WORLD, rank)
allocate(cont % arr(1, 1, 1))
if (rank == 0) then
cont % arr(1, 1, 1) = (1.0_dp, 2.0_dp)
endif
! This works fine ---> call MPI_Bcast(cont % arr(1, 1, 1), 1, MPI_COMPLEX16, 0, MPI_COMM_WORLD)
call MPI_Bcast(cont % arr(:, :, 1), 1, MPI_COMPLEX16, 0, MPI_COMM_WORLD)
print *, rank, " after Bcast: ", cont % arr(1, 1, 1)
call MPI_Finalize()
end subroutine test_intel_mpi
end module test_intel_mpi_mod
program test_mpi
use test_intel_mpi_mod
call test_intel_mpi()
end program test_mpi
The code is compiled simply as follows: `mpiifort -o test_mpi test_mpi.f90` and executed as `mpirun -np N ./test_mpi` (N = 1, 2, ...).
The output for N=2 is the following (also `-g -traceback` was added in this case):
0 after Bcast: (1.00000000000000,2.00000000000000)
1 after Bcast: (1.00000000000000,2.00000000000000)
forrtl: severe (174): SIGSEGV, segmentation fault occurred
Image PC Routine Line Source
test_mpi 000000000041475A Unknown Unknown Unknown
libpthread-2.17.s 00002AE5C8C0A5D0 Unknown Unknown Unknown
test_mpi 000000000040941D Unknown Unknown Unknown
test_mpi 0000000000409D79 Unknown Unknown Unknown
test_mpi 00000000004044C0 test_intel_mpi_mo 44 test_mpi.f90
test_mpi 00000000004044E0 MAIN__ 50 test_mpi.f90
test_mpi 0000000000403BA2 Unknown Unknown Unknown
libc-2.17.so 00002AE5C913B3D5 __libc_start_main Unknown Unknown
test_mpi 0000000000403AA9 Unknown Unknown Unknown
forrtl: severe (174): SIGSEGV, segmentation fault occurred
Image PC Routine Line Source
test_mpi 000000000041475A Unknown Unknown Unknown
libpthread-2.17.s 00002AB3DEFB75D0 Unknown Unknown Unknown
test_mpi 000000000040941D Unknown Unknown Unknown
test_mpi 0000000000409D79 Unknown Unknown Unknown
test_mpi 00000000004044C0 test_intel_mpi_mo 44 test_mpi.f90
test_mpi 00000000004044E0 MAIN__ 50 test_mpi.f90
test_mpi 0000000000403BA2 Unknown Unknown Unknown
libc-2.17.so 00002AB3DF4E83D5 __libc_start_main Unknown Unknown
test_mpi 0000000000403AA9 Unknown Unknown Unknown
The program crashes when it tries to exit the subroutine. The problem seems to be related to passing of the array section, `cont % arr(:, :, 1)`, to MPI_Bcast, as opposed to a reference to the first element, `cont % arr(1, 1, 1)` (this version of the call is left commented in the source code provided). At the same time, my understanding of the standard is that array sections, contiguous or not, are explicitly allowed in MPI 3.x (e.g., see https://www.mpi-forum.org/docs/mpi-3.1/mpi31-report/node409.htm).
Details in the source are important to reproduce the segfault:
- The crash happens only if MPI_Bcast is called -- commenting it out prevents the error
- The subroutine must be in a module
- The array must be at least 3-dimensional, allocatable, and be contained in a derived type object
- Non-blocking MPI_Ibcast, as well as other collectives implying broadcast (e.g., Allreduce) give the same result
Compiler/library versions:
Intel(R) Fortran Intel(R) 64 Compiler for applications running on Intel(R) 64, Version 19.1.1.217 Build 20200306
IntelMPI is from the same build: 2019.7.pre-intel-19.1.0.166-7
Output with I_DEBUG_MPI=6:
[0] MPI startup(): libfabric version: 1.9.0a1-impi
[0] MPI startup(): libfabric provider: psm2
[0] MPI startup(): Rank Pid Node name Pin cpu
[0] MPI startup(): 0 278604 l49 {0,1,2,3,4,5,6,7,16,17,18,19,20,21,22,23}
[0] MPI startup(): 1 278605 l49 {8,9,10,11,12,13,14,15,24,25,26,27,28,29,30,31}
[0] MPI startup(): I_MPI_ROOT=....
[0] MPI startup(): I_MPI_MPIRUN=mpirun
[0] MPI startup(): I_MPI_HYDRA_TOPOLIB=hwloc
[0] MPI startup(): I_MPI_INTERNAL_MEM_POLICY=default
[0] MPI startup(): I_MPI_DEBUG=6OS: CentOS Linux release 7.6.1810 (Core)
Kernel: 3.10.0-957.10.1.el7.x86_64