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1.                 From The Free On-line Dictionary of Computing (19 January 2023):
                   
   
   
                   
                     
   P4
      A macro/subroutine package for parallel programming by Rusty
      Lusk <lusk@anta.mcs.anl.gov>.  P4 uses monitors on shared
      memory machines and message passing on distributed memory
      machines.  It is implemented as a subroutine library for C
      and Fortran.  An enhancement of the "Argonne macros",
      PARMACS.
      (ftp://info.mcs.anl.gov/pub/p4t1.2.tar.Z).  E-mail:
      <p4@mcs.anl.gov>.