Hello,

I am running a MPI application on a single host, with a dual quadcore with hyperthreading on. (16 OS-visible processors), but just in debug mode (msvc2010) 32bit, with 2 mpi processes only.

mpirun -mca btl_tcp_if_exclude lo -np 1 prog1.exe : -np 1 prog2.exe

. when progr1.exe has 1 thread (mpi never initialized), everything works fine.

. when progr2.exe has 2 threads (1 thread with no call to mpi functions, and a second thread where mpi is initialized, through a default ctor of boost::mpi::environment, I think thos means just a call to MPI_Initialize() ), ompi_info gives "Threading support: No"

1. I start prog1, create addition thread boost::thread that handles MPI calls.

2. proceed to a point where both thread1 and threadMPI, not concurrently, call a function f().

f() initializes a global const std::string* X=null, to a static, this X is visible from both threads.

In fact, it appears at a certain point during a boost::mpi::broadcast, within threadMPI, boost::mpi calls MPI_Isend (point_to_point.cpp: 53), during this Isend, a 3rd thread (not threadMPI) is created and causes a call to f() which doesn't see X as !=nullptr.

I can see this while debugging with msvc, and stepping into MPI_Isend (i don't have the sources for it). At that moment, suddenly a new thread is created, and a call to f() is made.

This all sounds quite nightmarish.

I understand I haven't presented any specific code to receive an accurate answer, but any help is appreciated.

Regards,

MM