Hi, I have been building MPICH with the following configure options for a long time, mainly to keep my code “Valgrind-clean”: === ./configure \   --enable-g=dbg,meminit \   --with-device=ch3:sock \   --enable-romio === This setup worked reasonably well in the past, but recently I’ve been seeing occasional errors with address-sanitizer or valgrind (with 4.3.0 on a single node) such as: === Fatal error in internal_Allreduce_c: Unknown error class, error stack: internal_Allreduce_c(347)...................: MPI_Allreduce_c(sendbuf=0x7ffdeb0b8e90, recvbuf=0x7ffdeb0b8e98, count=1, dtype=0x4c00083a, MPI_SUM, comm=0x84000003) failed MPIR_Allreduce_impl(4826)...................: MPIR_Allreduce_allcomm_auto(4732)...........: MPIR_Allreduce_intra_recursive_doubling(115): MPIC_Sendrecv(266)..........................: MPIC_Wait(90)...............................: MPIR_Wait(751)..............................: MPIR_Wait_state(708)........................: MPIDI_CH3i_Progress_wait(187)...............: an error occurred while handling an event returned by MPIDI_CH3I_Sock_Wait() MPIDI_CH3I_Progress_handle_sock_event(385)..: MPIDI_CH3I_Socki_handle_read(3647)..........: connection failure (set=0,sock=1,errno=104:Connection reset by peer) === Is CH3 considered legacy? I would like to also ask:  1. What are the recommended configure options in 2025 for building MPICH in a way that works well with Valgrind?  2. Is it preferable now to move to CH4 (e.g. ch4:ofi or ch4:shm) when debugging with Valgrind?  3. Are there any other options (besides --enable-g=dbg,meminit) that you would suggest for catching memory errors while keeping Valgrind reports as clean as possible?  4. Is https://urldefense.us/v3/__https://github.com/pmodels/mpich/blob/main/doc/wi... <https://urldefense.com/v3/__https:/github.com/pmodels/mpich/blob/main/doc/wi... > up-to-date? Any guidance on the “best practice” configuration for this use case would be greatly appreciated. PETSc guys have some options about debug (https://urldefense.us/v3/__https://gitlab.com/petsc/petsc/-/blob/main/config... <https://urldefense.com/v3/__https:/gitlab.com/petsc/petsc/-/blob/main/config... >) but still uses CH3 by default.  However Satish uses the configuration described above, at least for valgrind CI. Thanks a lot, Eric -- Eric Chamberland, ing., M. Ing Professionnel de recherche GIREF/Université Laval On 2025-10-02 08:13, Balay, Satish wrote:

We currently use:

balay@petsc-gpu-02:~$ /nfs/gce/projects/petsc/soft/u22.04/mpich-4.3.0-p2-ucx/bin/mpichversion MPICH Version:      4.3.0 MPICH Release date: Mon Feb  3 09:09:47 AM CST 2025 MPICH ABI:          17:0:5 MPICH Device:       ch4:ucx MPICH configure:  --prefix=/nfs/gce/projects/petsc/soft/u22.04/mpich-4.3.0-p2-ucx --enable-shared --with-device=ch4:ucx --with-pm=hydra --enable-fast=no --enable-error-messages=all --enable-g=meminit --disable-java --without-hwloc --disable-opencl --without-cuda --without-hip MPICH CC:           gcc     -O0 MPICH CXX:          g++   -O0 MPICH F77:          gfortran   -O0 MPICH FC:           gfortran   -O0 MPICH features:     threadcomm

With:

    #MPICH OFI/UCX/valgrind     export FI_PROVIDER=^psm3     export UCX_SYSV_HUGETLB_MODE=n     export UCX_LOG_LEVEL=error

Satish ------------------------------------------------------------------------