from README.MPP, MM5V2.12
-------------------------

C. Procedures for testing bit for bit agreement between MPP and non-MPP
   versions of the model.

The following is a brief description of how to check the parallel
version of the model for bit for bit agreement with the non-MPP version.

  1.  In configure.user, disable all optimization for the MPP and non-MPP
      versions on your platform of choice.  This will entail editing
      Section 3 in the non-MPP configure.user and Section 7 in the 
      MPP configure.user.  Also remove any specifications of fast
      math libraries (e.g. the mass or essl libraries on the IBM.

  2.  If you are testing with the Blackadar PBL scheme (HIRPBL), edit
      the file physics/pbl_sfc/hirpbl/hirpbl.F and insert this line
      into the beginning of the file:

	  #define BIT_FOR_BIT_KLUDGE

      Be certain to remove this again when you are done testing.

  3.  Compile both the MPP and non-MPP versions, and run them using
      the same namelist file and data sets.

  4.  Compare the files.

      4a.  First try comparing the output files using the Unix
	   cmp command, e.g.:  cmp fort.41.par fort.41.seq .  If the
	   command returns without any output, the files are identical
	   bit for bit and the test has succeeded.

      4b.  If cmp finds differences

	   If differences are reported by the cmp command, that does
	   not necessarily mean that the output is substantively 
	   different -- there is garbage data around some output 
	   fields (extra row and column not used for cross point
	   variables) and this can generate spurious differences
           between the parallel and non-MPP output files.

	   Download the file:

	     http://www.mmm.ucar.edu/mp/WRF/diffv2.f

	   and compile with your fortran compiler.  On the DEC
	   machines, use the -convert big_endian option.  Then
	   use the resulting program as follows:

	      diffv2 fort.41.seq fort.41.par

	   If the non-garbage data in the files differ, the program
	   will generate two files, fort.88 and fort.98, which 
	   contain ASCII dumps of the fields that differ.  If the
	   diffv2 program writes a lot of stuff to the screen but
	   doesn't generate these files, then the fields all agree
	   bit for bit, and the test succeeds.

      4c.  If you are unable to get bit-for-bit agreement between
	   the MPP and non-MPP versions of the model for your 
	   configuration, please send us a note: mesouser@ucar.edu.
	    
   5. When you are done testing, be sure to undo the changes to the
      code that you may have done in steps 1 and 2, especially the
      #define in hirpbl.F.