On Jul 28, 2011, at 11:55 AM, Jose E. Roman wrote:

We are getting an undefined reference `MPI_Exscan'. This function is used in src/mat/impls/nest/matnest.c. If I am not wrong, MPI_Exscan was introduced in MPI-2 but was not available in the previous standard. Apparently, the machine where we are compiling is very old and has MPI-1 only.

I guess there should be a PETSC_HAVE_MPI_EXSCAN test in configure.

Correct, whoever used that MPI 2 function in PETSc is obligated to protect it. Barry

Jose