The Detailed Information can be found at Displaying MPI Debug Information

The I_MPI_DEBUG environment variable provides a convenient way to get detailed information about an MPI application at runtime. You can set the variable value from 0 (the default value) to 1000. The higher the value, the more debug information you get.

High values of I_MPI_DEBUG can output a lot of information and significantly reduce performance of your application. A value of I_MPI_DEBUG=5 is generally a good starting point, which provides sufficient information to find common errors.

Displaying MPI Debug Information

To redirect the debug information output from stdout to stderr or a text file, use the I_MPI_DEBUG_OUTPUT environment variable

$ mpirun -genv I_MPI_DEBUG=5 -genv I_MPI_DEBUG_OUTPUT=debug_output.txt -n 32 ./mpi_program

I_MPI_DEBUG Arguments

<level>	Indicate the level of debug information provided.
0	Output no debugging information. This is the default value.
1	Output libfabric* version and provider.
2	Output information about the tuning file used.
3	Output effective MPI rank, pid and node mapping table.
4	Output process pinning information.
5	Output environment variables specific to the Intel® MPI Library.
> 5	Add extra levels of debug information.

<flags>	Comma-separated list of debug flags
pid	Show process id for each debug message.
tid	Show thread id for each debug message for multithreaded library.
time	Show time for each debug message.
datetime	Show time and date for each debug message.
host	Show host name for each debug message.
level	Show level for each debug message.
scope	Show scope for each debug message.
line	Show source line number for each debug message.
file	Show source file name for each debug message.
nofunc	Do not show routine name.
norank	Do not show rank.
nousrwarn	Suppress warnings for improper use case (for example, incompatible combination of controls).
flock	Synchronize debug output from different process or threads.
nobuf	Do not use buffered I/O for debug output.

References:

1. Displaying MPI Debug Information
2. Developer Reference: I_MPI_DEBUG