Now that Silicon Graphics, Inc (SGI) has bought Cray Research Inc. (CRI), SGI has three separate MPI implementations for its three types of machines -- parallel vector (e.g. J90/C90/T90), Irix (including Origin 2000), and T3E. These implementations all have different roots and are therefore treated as separate implementations here. SGI is in the process of merging at least two of the implementations, In each case, MPI is part of a package called MPT (Message Passing Toolkit) that also includes SGI/Cray's shmem library and PVM.