Can you confirm which MPI library you binary is linked with using ldd? Adding -v to the mpirun command should also provide some clues in the PMI client/server traffic. Ken -----Original Message----- From: Joachim Jenke via discuss <[email protected] <mailto:[email protected]>> Reply-To: "[email protected] <mailto:[email protected]>" <[email protected] <mailto:[email protected]>> Date: Wednesday, July 3, 2024 at 5:16 AM To: "[email protected] <mailto:[email protected]>" <[email protected] <mailto:[email protected]>> Cc: Joachim Jenke <[email protected] <mailto:[email protected]>> Subject: [mpich-discuss] All processes only find themselfs Hi all, after upgrading my notebook to Ubuntu 24.04, each processes thinks that MPI_COMM_WORLD only consists of its own process: $ mpirun -np 2 -l ./a.out [1] Hello, I am 0 of 1 tasks. [0] Hello, I am 0 of 1 tasks. Any suggestions what could go wrong? $ mpirun --version HYDRA build details: Version: 4.2.0 Release Date: Fri Feb 9 12:29:21 CST 2024 CC: gcc -Wdate-time -D_FORTIFY_SOURCE=3 -g -O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -ffile-prefix-map=/build/mpich-C3oteG/mpich-4.2.0=. -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -fdebug-prefix-map=/build/mpich-C3oteG/mpich-4.2.0=/usr/src/mpich-4.2.0-5build3 -Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro Configure options: '--with-hwloc-prefix=/usr' '--with-device=ch4:ucx' 'FFLAGS=-O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -ffile-prefix-map=/build/mpich-C3oteG/mpich-4.2.0=. -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -fcf-protection -fdebug-prefix-map=/build/mpich-C3oteG/mpich-4.2.0=/usr/src/mpich-4.2.0-5build3 -fallow-invalid-boz -fallow-argument-mismatch' '--prefix=/usr' 'CFLAGS=-g -O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -ffile-prefix-map=/build/mpich-C3oteG/mpich-4.2.0=. -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -fdebug-prefix-map=/build/mpich-C3oteG/mpich-4.2.0=/usr/src/mpich-4.2.0-5build3' 'LDFLAGS=-Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=3' Process Manager: pmi Launchers available: ssh rsh fork slurm ll lsf sge manual persist Topology libraries available: hwloc Resource management kernels available: user slurm ll lsf sge pbs cobalt Demux engines available: poll select Best Joachim -- Dr. rer. nat. Joachim Jenke IT Center Group: High Performance Computing Division: Computational Science and Engineering RWTH Aachen University Seffenter Weg 23 D 52074 Aachen (Germany) Tel: +49 241 80- 24765 Fax: +49 241 80-624765 [email protected] <mailto:[email protected]> https://urldefense.us/v3/__http://www.itc.rwth-aachen.de__;!!G_uCfscf7eWS!bL...