<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head><body><div>I'm trying to solve a system with a single, non-constant, null space vector, confirmed by passing the MatNullSpaceTest. Solving the system works fine with -pc_type ilu on one or multiple procs. It also works fine with -pc_type lu on multiple procs but fails on a single proc. Any idea what could be wrong?<br /><br />Chris<br /><br />[0]PETSC ERROR: *** unknown floating point error occurred ***<br />[0]PETSC ERROR: The specific exception can be determined by running in a debugger. When the<br />[0]PETSC ERROR: debugger traps the signal, the exception can be found with fetestexcept(0x3f)<br />[0]PETSC ERROR: where the result is a bitwise OR of the following flags:<br />[0]PETSC ERROR: FE_INVALID=0x1 FE_DIVBYZERO=0x4 FE_OVERFLOW=0x8 FE_UNDERFLOW=0x10 FE_INEXACT=0x20<br />[0]PETSC ERROR: Try option -start_in_debugger<br />[0]PETSC ERROR: likely location of problem given in stack below<br />[0]PETSC ERROR: --------------------- Stack Frames ------------------------------------<br />[0]PETSC ERROR: The line numbers in the error traceback are not always exact.<br />[0]PETSC ERROR: #1 PetscDefaultFPTrap() at /cm/shared/apps/petsc/oneapi/build/src/src/sys/error/fp.c:487<br />[0]PETSC ERROR: #2 VecMDot_Seq() at /cm/shared/apps/petsc/oneapi/build/src/src/vec/vec/impls/seq/dvec2.c:189<br />[0]PETSC ERROR: #3 VecMXDot_MPI_Default() at /cm/shared/apps/petsc/oneapi/build/src/include/../src/vec/vec/impls/mpi/pvecimpl.h:96<br />[0]PETSC ERROR: #4 VecMDot_MPI() at /cm/shared/apps/petsc/oneapi/build/src/src/vec/vec/impls/mpi/pvec2.c:25<br />[0]PETSC ERROR: #5 VecMXDot_Private() at /cm/shared/apps/petsc/oneapi/build/src/src/vec/vec/interface/rvector.c:1112<br />[0]PETSC ERROR: #6 VecMDot() at /cm/shared/apps/petsc/oneapi/build/src/src/vec/vec/interface/rvector.c:1184<br />[0]PETSC ERROR: #7 MatNullSpaceRemove() at /cm/shared/apps/petsc/oneapi/build/src/src/mat/interface/matnull.c:359<br />[0]PETSC ERROR: #8 KSP_RemoveNullSpace() at /cm/shared/apps/petsc/oneapi/build/src/include/petsc/private/kspimpl.h:322<br />[0]PETSC ERROR: #9 KSP_PCApply() at /cm/shared/apps/petsc/oneapi/build/src/include/petsc/private/kspimpl.h:382<br />[0]PETSC ERROR: #10 KSPInitialResidual() at /cm/shared/apps/petsc/oneapi/build/src/src/ksp/ksp/interface/itres.c:64<br />[0]PETSC ERROR: #11 KSPSolve_GMRES() at /cm/shared/apps/petsc/oneapi/build/src/src/ksp/ksp/impls/gmres/gmres.c:226<br />[0]PETSC ERROR: #12 KSPSolve_Private() at /cm/shared/apps/petsc/oneapi/build/src/src/ksp/ksp/interface/itfunc.c:898<br />[0]PETSC ERROR: #13 KSPSolve() at /cm/shared/apps/petsc/oneapi/build/src/src/ksp/ksp/interface/itfunc.c:1070<br />[0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------<br />[0]PETSC ERROR: Floating point exception<br />[0]PETSC ERROR: trapped floating point error<br />[0]PETSC ERROR: See <a href="https://urldefense.us/v3/__https://petsc.org/release/faq/__;!!G_uCfscf7eWS!dXxAqHgHbtticGbE-cswI2ylVIt4A7Fn68LPFMyFtpJByLQtJocy5JF-Vf5Vzr_FbcWB1l7ve_2l9CdBfaa2Fyw$">https://petsc.org/release/faq/</a> for trouble shooting.<br />[0]PETSC ERROR: Petsc Release Version 3.19.4, Jul 31, 2023 <br />[0]PETSC ERROR: ./refresco on a named marclus3login2 by cklaij Thu Nov 7 11:03:22 2024<br />[0]PETSC ERROR: Configure options --prefix=/cm/shared/apps/petsc/oneapi/3.19.4-dbg --with-mpi-dir=/cm/shared/apps/intel/oneapi/mpi/2021.4.0 --with-x=0 --with-mpe=0 --with-debugging=1 --download-superlu_dist=../superlu_dist-8.1.2.tar.gz --with-blaslapack-dir=/cm/shared/apps/intel/oneapi/mkl/2021.4.0 --download-parmetis=../parmetis-4.0.3-p9.tar.gz --download-metis=../metis-5.1.0-p11.tar.gz --with-packages-build-dir=/cm/shared/apps/petsc/oneapi/build --with-ssl=0 --with-shared-libraries=1 CFLAGS="-std=gnu11 -Wall -funroll-all-loops -O3 -DNDEBUG" CXXFLAGS="-std=gnu++14 -Wall -funroll-all-loops -O3 -DNDEBUG" COPTFLAGS="-std=gnu11 -Wall -funroll-all-loops -O3 -DNDEBUG" CXXOPTFLAGS="-std=gnu++14 -Wall -funroll-all-loops -O3 -DNDEBUG" FCFLAGS="-funroll-all-loops -O3 -DNDEBUG" F90FLAGS="-funroll-all-loops -O3 -DNDEBUG" FOPTFLAGS="-funroll-all-loops -O3 -DNDEBUG"<br />Abort(72) on node 0 (rank 0 in comm 0): application called MPI_Abort(MPI_COMM_WORLD, 72) - process 0</div><div dir="ltr" style="mso-line-height-rule:exactly;-webkit-text-size-adjust:100%;font-size:1px;direction:ltr;"><table dir="ltr" cellpadding="0" cellspacing="0" border="0" 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