core: fix Stokesian Dynamics MPI deadlock on missing per-type radius (bug-sweep #25)#5359
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…(bug-sweep #25) Bug: StokesianDynamics::propagate_vel_pos evaluated radii.at(p.type) inside the rank-0-only block, between the collective gather_buffer and the collective scatter_buffer. For a particle whose type has no registered radius, at() threw std::out_of_range on rank 0, which unwound out of the integration loop (no parallel_try_catch on that call path) before reaching MPI_Scatterv. The other ranks blocked forever in the matching MPI_Scatterv -> indefinite MPI deadlock (multi-rank) or an uncoordinated std::out_of_range abort (serial). Fix: replace radii.at() with radii.find() and, on a missing type, register a coordinated runtime error via runtimeErrorMsg() instead of throwing. The rank-0 branch still falls through to the collective scatter_buffer (shipping zeroed velocities), so every rank reaches MPI_Scatterv and no deadlock occurs. The integration loop's collective check_runtime_errors(comm_cart) then turns the registered message into a clean cross-rank ESPResSo runtime error ("Stokesian Dynamics: no radius defined for particle type N"). This mirrors the existing SD precondition checks in integrate.cpp. Test: testsuite/python/stokesian_missing_radius.py (NO_MPI) launches the offending scenario as a child mpiexec -n 2 job under a 45 s timeout; on the unfixed core it times out (deadlock), on the fixed core it exits cleanly with the coordinated error. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Bug: StokesianDynamics::propagate_vel_pos evaluated radii.at(p.type) inside
the rank-0-only block, between the collective gather_buffer and the collective
scatter_buffer. For a particle whose type has no registered radius, at() threw
std::out_of_range on rank 0, which unwound out of the integration loop (no
parallel_try_catch on that call path) before reaching MPI_Scatterv. The other
ranks blocked forever in the matching MPI_Scatterv -> indefinite MPI deadlock
(multi-rank) or an uncoordinated std::out_of_range abort (serial).
Fix: replace radii.at() with radii.find() and, on a missing type, register a
coordinated runtime error via runtimeErrorMsg() instead of throwing. The rank-0
branch still falls through to the collective scatter_buffer (shipping zeroed
velocities), so every rank reaches MPI_Scatterv and no deadlock occurs. The
integration loop's collective check_runtime_errors(comm_cart) then turns the
registered message into a clean cross-rank ESPResSo runtime error
("Stokesian Dynamics: no radius defined for particle type N"). This mirrors the
existing SD precondition checks in integrate.cpp.
Test: testsuite/python/stokesian_missing_radius.py (NO_MPI) launches the
offending scenario as a child mpiexec -n 2 job under a 45 s timeout; on the
unfixed core it times out (deadlock), on the fixed core it exits cleanly with
the coordinated error.
Co-Authored-By: Claude Opus 4.8 noreply@anthropic.com
🤖 Generated with Claude Code