




          date:     June 1, 1984
           
          to:       HGraph DECUS Users
           
          from:     Dennis V. Jensen
                    Ames Laboratory
                    310 Metallurgy
                    Ames, Iowa  50011     515/294-4823
           
          subject:  HGraf2 - The Second HGraph DECUS Release.


               The initial DECUS release of HGraph was at the Fall
          1983 Symposium.  It was released to the RT, RSX, and VAX
          SIG tapes.  The RSX release is known to not be  complete
          in  the  ASCII  text.  Release one was coded entirely in
          DEC Fortran 66 compatible code.

               This second release is  being  distributed  at  the
          Spring  1984  symposium.  Included in the second release
          is a new  WRTSTR  (extracted  as  WRTST2.*)  which  will
          generate  characters as vectors;  it is not dependent on
          the Visual 550 character generator.  Also,  there  is  a
          cubic   spline   interpolation   line   drawing  routine
          (extracted as SMOOTH.*) which  is  compatible  with  the
          DASHLN calling convention.

               Release two is coded  in  FLECS.   This  structured
          Fortran  code is contained in the .FLX files.  The FLECS
          generated Fortran 66 code is in  the  .FOR  files.   The
          HGraph  document  is  in  the  HGraph.DOC  file with the
          associated Runoff file as HGraph.RNO.   An  RT-11  FLECS
          translator  FLECS.*  (RE:   RT SIG Fall 81 Tape) is also
          included for reference.  Refer to the VAX  Fall  82  SIG
          Tape  [VAX82B.FORDAERO.UTIL.FORDUTIL]  (or  something to
          this effect) for a VMS FLECS translator.

               PLOT3D.FOR is included as a separate file.  A FLECS
          version is not included as it does not exist.  PLOT3D is
          known to have bugs, but will work for  many  of  the  3D
          plots   you  may  wish  to  do.   Although  considerable
          development is occuring at the Ames Laboratory on the 2D
          versions  of  HGraph,  no  additional  work is currently
          planned for the 3D code;  PLOT3D should  be  treated  as
          unsupported.

               Modifications included in this distribution correct
          a  problem  detected  in  calls to subroutine XAXIS when
          threaded   code   is   produced.    This   problem    is
          characterized  by  a  "?MON-F-Trap  to  4  NNNNNN" error
          message being produced in response to a call  subroutine
          AXIS.   The  solution  to  the  problem  is  to generate
          in-line EIS code for subroutine XAXIS.  Included in this

          HGraf2 - The Second HGraph DECUS Release.         PAGE 2



          distribution  is a version of HGRAPH.FLX with subroutine
          XAXIS removed, file  XAXIS.FLX.   The  indirect  command
          file HGRAPH.BLD will build an HGRAPH object library that
          includes the SMOOTH and PLOT3D features as well  as  the
          problem correction.

               When using HGRAPH it is  common  to  encounter  the
          message  "LINK-F-Library  list  overflow".  Increase the
          library list size with the /P switch when linking.   For
          example:
          		r link
          		prog/P:400=prog,sy:hgraph

               A  commonly  occuring  run-time  error  when  using
          HGRAPH is "?MON-F-Trap to 4 NNNNNN".  This message often
          indicates a lack of program stack space.   The  solution
          is  to  increase the amount of program stack space using
          the /B linker option.  For example:
          		r link
          		prog/B:1200=prog,sy:hgraph
          The default value of B is 1000 octal.  

               In fact, you  may  notice  that  this  problem  has
          basically  the  same  outward  appearance  as  the XAXIS
          problem mentioned above, the solution of  which  was  to
          use inline code.  Inline code requires less stack space,
          so users of inline code may not  need  to  increase  the
          stack.   Users of threaded code will typically need more
          stack.  It is quite likely  that  if  the  stack  is  of
          sufficient  size,  there  is  no  need  for  XAXIS to be
          inline.  I have not verified this, though.

               All code included in this distribution  is  in  the
          public  domain  and  may not be marketed for profit.  It
          may be altered without the explicit  permission  of  the
          authors.   Any  corrections or significant modifications
          to HGraph are of interest to  the  authors  and  may  be
          communicated  to  the  address  above.   The authors and
          their  employers  assume  no  responsibility   for   the
          correctness   or  the  appropriatness  of  the  software
          included in this distribution.

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