Data Race due to num_error variable #585
Description
What type of issue is this?
- Bug in the code or other problem
- Inadequate/incorrect documation
- Feature request
If this is a bug report, please use the following template.
Otherwise, please delete the rest of the template.
Where does this bug appear?
Check all that apply:
- MacOS
- Linux
- Cray
- GCC
- Clang
- Intel compiler
- MPICH and derivatives (MVAPICH2, Intel MPI, Cray MPI, etc.)
- Open-MPI
Operating system
What is the output of uname -a?
Linux 299fdde96882 5.4.72-microsoft-standard-WSL2 #1 SMP Wed Oct 28 23:40:43 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Compiler
What is the output of ${COMPILER} -v or ${COMPILER} --version?
clang version 10.0.1
PRK build information
Please attach or inline make.defs.
#name of MPI C compiler, e.g. mpiicc, mpicc
MPICC=
#name of C compiler, e.g. icc, xlc, gcc
CC=clang-10
#name of MPI Fortran compiler, e.g. mpifort, mpif90
MPIF90=
#name of Fortran compiler, e.g. ifort, xlf_r, gfortran
FC=
#name of compile line flag enabling OpenMP, e.g. -openmp, -qopenmp, -fopenmp
OPENMPFLAG=-fopenmp
OFFLOADFLAG=
#default compiler optimization flags
DEFAULT_OPT_FLAGS:=
Output showing problem
I detected a data race occurring in all of the OpenMP Kernels except for Refcount. All the Kernels have the same data race in involving the num_error variable, specifically when one thread will try to write num_error=1 while another will try to read bail_out(num_error). An example from branch:
#pragma omp parallel private(i, my_ID, iter, aux, nfunc, rank) reduction(+:total)
{
int * RESTRICT vector; int * RESTRICT index;
#pragma omp master
{
nthread = omp_get_num_threads();
if (nthread != nthread_input) {
num_error = 1;
printf("ERROR: number of requested threads %d does not equal ",
nthread_input);
printf("number of spawned threads %d\n", nthread);
}
else {
printf("Number of threads = %d\n", nthread_input);
printf("Vector length = %d\n", vector_length);
printf("Number of iterations = %d\n", iterations);
printf("Branching type = %s\n", branch_type);
#if RESTRICT_KEYWORD
printf("No aliasing = on\n");
#else
printf("No aliasing = off\n");
#endif
}
}
bail_out(num_error);
The data race occurs between lines 9 and 26 in this snippet, or lines 207 and 224 of branch.c. I found this data race using the Coderrect Scanner https://coderrect.com/
Please do not attach screenshots of your terminal.