## Summary Ubuntu has an issue with GROMACS 2022.5 and GCC 12.3 on ppc64le, with multiple failures in SelectionUnitTests https://bugs.launchpad.net/ubuntu/+source/gcc-12/+bug/2009247, [buildlog_ubuntu-lunar-ppc64el.gromacs_2022.5-2_BUILDING.txt.gz](/uploads/26a791bafce6ff40d9af9a556712e754/buildlog_ubuntu-lunar-ppc64el.gromacs_2022.5-2_BUILDING.txt.gz) > The failure persists when disabling LTO and when downgrading from -O3 to -O2. > The failure also is not seen in Debian, where this built successfully with gcc-12. The issue can be reproduced on `dev-power9` with GCC 12.3.0 built from source and recent `main` (c61c11f34b01aaf48340e98193bf9058e603572f). ## Exact steps to reproduce On `dev-power9`: ```console $ module load `/nethome/aland/modules/modulefiles/gcc/12.3.0-ppc64 cmake/3.23.1 $ cmake ../.. -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ [...] $ ./bin/selection-test [....] [==========] 201 tests from 11 test suites ran. (314 ms total) [ PASSED ] 199 tests. [ FAILED ] 2 tests, listed below: [ FAILED ] SelectionCollectionDataTest.ComputesMassesAndCharges [ FAILED ] SelectionCollectionDataTest.HandlesOverlappingRealRanges 2 FAILED TESTS $ ./bin/gmx -version [...] GROMACS version: 2024-dev-20230712-c61c11f34b GIT SHA1 hash: c61c11f34b01aaf48340e98193bf9058e603572f Precision: mixed Memory model: 64 bit MPI library: thread_mpi OpenMP support: enabled (GMX_OPENMP_MAX_THREADS = 128) GPU support: disabled SIMD instructions: IBM_VSX CPU FFT library: fftw-3.3.8 GPU FFT library: none Multi-GPU FFT: none TNG support: enabled Hwloc support: disabled Tracing support: disabled C compiler: /nethome/aland/modules/gcc/12.3.0-ppc64/bin/gcc GNU 12.3.0 C compiler flags: -Wno-array-bounds -fexcess-precision=fast -funroll-all-loops -mcpu=power9 -mtune=power9 -mvsx -Wall -Wno-unused -Wunused-value -Wunused-parameter -Wextra -Wno-sign-compare -Wpointer-arith -Wundef -Werror=stringop-truncation -Wno-missing-field-initializers -O3 -DNDEBUG C++ compiler: /nethome/aland/modules/gcc/12.3.0-ppc64/bin/g++ GNU 12.3.0 C++ compiler flags: -Wno-array-bounds -fexcess-precision=fast -funroll-all-loops -mcpu=power9 -mtune=power9 -mvsx -Wall -Wextra -Wpointer-arith -Wmissing-declarations -Wundef -Wstringop-truncation -Wno-missing-field-initializers -Wno-cast-function-type-strict -fopenmp -O3 -DNDEBUG BLAS library: LAPACK library: ``` ## Possible fixes Ubuntu opened [a bug report for GCC](https://bugs.launchpad.net/ubuntu/+source/gcc-12/+bug/2009247). For us, I think adding a known issue is enough.