Each of the files here contain only a partial implementation of DDI.
Their use, therefore, is contraindicated.

            the first three have not changed since 2006:

ddio3k.src: this is for the SGI Origin 3000 series, using MIPS.
            It is the original version, and was a working port of
            the original DDI functionality.  Like other files here,
            no one ever included DDI version 2 or 3 functionality
            into this port.
ddit3e.src: this was used on the Cray T3E and Compaq superclusters,
            quite successfully.  Briefly, on XD1, using "GPSHMEM".
            Today it is still asked for during a Cray X1 (vector)
            compile, but I have my doubts about that working.
            Small machine differences are mediated by *T3E, *DEC,
            *XD1, and *CX1 lines.
ddixt3.src: intended for use on the Cray XT-3 line, where the lack
            of "atomic" operations always made DLB problematic.
            Hence it was never really successfully used.
            The more recent XT models all use MPI-1, not this file.

            early 2010:

ddishm.src: the most recent version.  Probably the one to go with!
            It is not currently used by any build in our scripting.
            This requires use of -DSHMEM64 when compiling zunix.c

            This is very likely for the SGI Altix/ICE products,
            although it came to me as "company number 3"'s port.
