I wanted to bring up the ZeroByteTypeBug flag in ScaLAPACK as I do not see any mention of it in the documentation. Although this may technically be an issue with BLACS instead of ScaLAPACK...
I just set up (compiled) ScaLAPACK version 2.0.2 on a machine with OpenMPI. While trying to test the solver PSSYEVR to obtain all eigenvalues and eigenvectors, I discovered that some messages are packed with MPI_Pack in the method BI_Pack that are zero bytes. This caused a segmentation fault. Looking through the source code (for example, BI_GetMpiGeType.c), I found some comments about mpich having difficulty with zero byte messages. There is a work around already in place, but it requires setting the compile flag ZeroByteTypeBug. Setting this fixed the segmentation faults and the PSSYEVR solver seems to be working properly.
If anyone else has problems with this, I just changed in SLmake.inc the line
CDEFS = -DAdd_
CDEFS = -DAdd_ -D ZeroByteTypeBug
and ran "make clean" followed by "make all" for the ScaLAPACK code. You will probably want to recompile your program as well.
Anyway, I do not see anything in the ScaLAPACK documentation about this flag. Perhaps it is there and I just missed it. If it is not there, adding something about the ZeroByteTypeBug flag could really save time for some people