SCANMACS is a package of portable C Macros that instantiate high 
performance scan (parallel prefix) operations.  The interface to these
operations is similar to that of the HPF 1.1 scan library functions.

SCANMACS is documented in http://www.cs.cmu.edu/afs/cs.cmu.edu/project/iwarp/member/pdinda/PAPERS/ScanMacs/report.ps

