Questions for the Community

For convenience we summarize here those questions on which we would particularly welcome feedback:

• Should the alignment restrictions in the current implementation be removed, or do the PBLAS provide sufficient functionality the way they are ? (see Sect. 5.1)
• When a PBLAS routine is called by every process in the grid, it is required that the code operates successfully accordingly to the SPMD programming model. However, it is also necessary that the PBLAS routines recognize the scope of their operands for efficiency purposes. Is it reasonable to slightly depart from the SPMD programming model for efficiency purposes ? (see Sect. 6)
• Should the PBLAS be able to recognize and take advantage of replicated operands across process rows or columns ? For example, a column replicated vector is a vector distributed over the rows of a process column, and every other column owns an aligned copy of that vector. If such an operand is to be set on output, should all the distinct copies of the replicated array be updated ? (see Sect. 6)
• Should other vector increment values (e.g INCX) be supported beside and DESCX(1) ? (see Sect. 6)
• Is the current set of PBLAS routines sufficient or should we consider adding more routines and increase the PBLAS functionality and usefulness ? (see Sect. 6)