I'm trying to track down the cause of an inconsistency in valgrind's heap allocation analysis. This arose when using the MPICH downloaded by PETSc. To reproduce, I run the following and note that the number of allocations and frees are different (yet all blocks are reported free). printf "#include<mpi.h>\nint main(int a,char **b){MPI_Init(&a,&b);MPI_Finalize();}" > t.c && $PETSC_DIR/$PETSC_ARCH/bin/mpicc t.c && valgrind ./a.out ==8578== Memcheck, a memory error detector ==8578== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==8578== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info ==8578== Command: ./a.out ==8578== ==8578== ==8578== HEAP SUMMARY: ==8578== in use at exit: 0 bytes in 0 blocks ==8578== total heap usage: *1,979 allocs, 1,974 frees*, 4,720,483 bytes allocated ==8578== ==8578== All heap blocks were freed -- no leaks are possible ==8578== ==8578== For counts of detected and suppressed errors, rerun with: -v ==8578== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0) The above was generated on Ubuntu 18.04.2 LTS, using MPICH 3.3b1 as configured in the attached config.log (which was done automatically for me by PETSc master). ---------- Forwarded message --------- Von: Smith, Barry F. <[email protected]> Date: Mo., 22. Juli 2019 um 20:24 Uhr Subject: Re: [petsc-dev] MPICH from --download-mpich reports inconsistent allocs/frees with valgrind To: petsc-dev <[email protected]> Cc: Patrick Sanan <[email protected]>, Balay, Satish < [email protected]> Bug report to MPICH.

On Jul 22, 2019, at 1:22 PM, Balay, Satish via petsc-dev < [email protected]> wrote:

Hm - I don't think we were monitoring the leaks via valgrind that closely.

Looking at my old mpich install - I don't see a problem - so likely its an issue with newer versions of mpich.

Satish

------- balay@sb /home/balay/tmp $ mpichversion MPICH Version: 3.3 MPICH Release date: Wed Nov 21 11:32:40 CST 2018 MPICH Device: ch3:sock MPICH configure: --prefix=/home/balay/soft/mpich-3.3 MAKE=/usr/bin/gmake --libdir=/home/balay/soft/mpich-3.3/lib CC=gcc CFLAGS=-fPIC -g -O AR=/usr/bin/ar ARFLAGS=cr CXX=g++ CXXFLAGS=-g -O -fPIC F77=gfortran FFLAGS=-fPIC -g -O FC=gfortran FCFLAGS=-fPIC -g -O --enable-shared --with-device=ch3:sock --with-pm=hydra --enable-fast=no --enable-error-messages=all --enable-g=meminit MPICH CC: gcc -fPIC -g -O -O0 MPICH CXX: g++ -g -O -fPIC -O0 MPICH F77: gfortran -fPIC -g -O -O0 MPICH FC: gfortran -fPIC -g -O -O0 MPICH Custom Information: balay@sb /home/balay/tmp $ printf "#include<mpi.h>\nint main(int a,char**b){MPI_Init(&a,&b);MPI_Finalize();}" > t.c && mpicc t.c && valgrind ./a.out ==9024== Memcheck, a memory error detector ==9024== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==9024== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==9024== Command: ./a.out ==9024== ==9024== ==9024== HEAP SUMMARY: ==9024== in use at exit: 0 bytes in 0 blocks ==9024== total heap usage: 1,886 allocs, 1,886 frees, 4,884,751 bytes allocated ==9024== ==9024== All heap blocks were freed -- no leaks are possible ==9024== ==9024== For lists of detected and suppressed errors, rerun with: -s ==9024== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0) balay@sb /home/balay/tmp

On Mon, 22 Jul 2019, Patrick Sanan via petsc-dev wrote:

...

It was pointed out to me that valgrind memcheck reports inconsistent heap usage information when running PETSc examples. All blocks are reported freed, yet the number of allocations and frees are different. My guess as to what's going on is that this is an MPICH issue, as I can reproduce the behavior with a minimal MPI program.

...

From the PETSc perspective, is this a known issue? I'm wondering if this inconsistency was always there, whether it's worth looking into more, etc.

Here's a 1-liner to reproduce, using a PETSc master build with --download-mpich (though note that this doesn't use anything from PETSc except the MPICH it builds for you).

printf "#include<mpi.h>\nint main(int a,char **b){MPI_Init(&a,&b);MPI_Finalize();}" > t.c && $PETSC_DIR/$PETSC_ARCH/bin/mpicc t.c && valgrind ./a.out

==14242== Memcheck, a memory error detector ==14242== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==14242== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info ==14242== Command: ./a.out ==14242== ==14242== ==14242== HEAP SUMMARY: ==14242== in use at exit: 0 bytes in 0 blocks ==14242== total heap usage: *1,979 allocs, 1,974 frees*, 4,720,483 bytes allocated ==14242== ==14242== All heap blocks were freed -- no leaks are possible ==14242== ==14242== For counts of detected and suppressed errors, rerun with: -v ==14242== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)