# dtout.f

          SUBROUTINE DTOUT (N, NELT, IA, JA, A, ISYM, SOLN, RHS, IUNIT, JOB)
    C***BEGIN PROLOGUE  DTOUT
    C***PURPOSE  Write out SLAP Triad Format Linear System.
    C            Routine to write out a SLAP Triad format matrix and right
    C            hand side and solution to the system, if known.
    C***LIBRARY   SLATEC (SLAP)
    C***CATEGORY  N1
    C***TYPE      DOUBLE PRECISION (STOUT-S, DTOUT-D)
    C***KEYWORDS  DIAGNOSTICS, LINEAR SYSTEM, SLAP SPARSE
    C***AUTHOR  Seager, Mark K., (LLNL)
    C             Lawrence Livermore National Laboratory
    C             PO BOX 808, L-60
    C             Livermore, CA 94550 (510) 423-3141
    C             seager@llnl.gov
    C***DESCRIPTION
    C
    C *Usage:
    C     INTEGER N, NELT, IA(NELT), JA(NELT), ISYM, IUNIT, JOB
    C     DOUBLE PRECISION A(NELT), SOLN(N), RHS(N)
    C
    C     CALL DTOUT( N, NELT, IA, JA, A, ISYM, SOLN, RHS, IUNIT, JOB )
    C
    C *Arguments:
    C N      :IN       Integer
    C         Order of the Matrix.
    C NELT   :IN       Integer.
    C         Number of non-zeros stored in A.
    C IA     :IN       Integer IA(NELT).
    C JA     :IN       Integer JA(NELT).
    C A      :IN       Double Precision A(NELT).
    C         These arrays should hold the matrix A in the SLAP
    C         Triad format.  See "Description", below.
    C ISYM   :IN       Integer.
    C         Flag to indicate symmetric storage format.
    C         If ISYM=0, all non-zero entries of the matrix are stored.
    C         If ISYM=1, the matrix is symmetric, and only the lower
    C         triangle of the matrix is stored.
    C SOLN   :IN       Double Precision SOLN(N).
    C         The solution to the linear system, if known.  This array
    C         is accessed if and only if JOB is set to print it out,
    C         see below.
    C RHS    :IN       Double Precision RHS(N).
    C         The right hand side vector.  This array is accessed if and
    C         only if JOB is set to print it out, see below.
    C IUNIT  :IN       Integer.
    C         Fortran logical I/O device unit number to write the matrix
    C         to.  This unit must be connected in a system dependent fashion
    C         to a file or the console or you will get a nasty message
    C         from the Fortran I/O libraries.
    C JOB    :IN       Integer.
    C         Flag indicating what I/O operations to perform.
    C         JOB = 0 => Print only the matrix.
    C             = 1 => Print matrix and RHS.
    C             = 2 => Print matrix and SOLN.
    C             = 3 => Print matrix, RHS and SOLN.
    C
    C *Description:
    C       The format for the output is as follows.  On  the first line
    C       are counters and flags: N, NELT, ISYM, IRHS, ISOLN.  N, NELT
    C       and ISYM are described above.  IRHS is  a flag indicating if
    C       the RHS was  written out (1 is  yes, 0 is  no).  ISOLN  is a
    C       flag indicating if the SOLN was written out  (1 is yes, 0 is
    C       no).  The format for the fist line is: 5i10.  Then comes the
    C       NELT Triad's IA(I), JA(I) and A(I), I = 1, NELT.  The format
    C       for  these lines is   :  1X,I5,1X,I5,1X,D16.7.   Then  comes
    C       RHS(I), I = 1, N, if IRHS = 1.  Then  comes SOLN(I), I  = 1,
    C       N, if ISOLN = 1.  The format for these lines is: 1X,D16.7.
    C
    C       =================== S L A P Triad format ===================
    C       This routine requires that the  matrix A be   stored in  the
    C       SLAP  Triad format.  In  this format only the non-zeros  are
    C       stored.  They may appear in  *ANY* order.  The user supplies
    C       three arrays of  length NELT, where  NELT is  the number  of
    C       non-zeros in the matrix: (IA(NELT), JA(NELT), A(NELT)).  For
    C       each non-zero the user puts the row and column index of that
    C       matrix element  in the IA and  JA arrays.  The  value of the
    C       non-zero  matrix  element is  placed   in  the corresponding
    C       location of the A array.   This is  an  extremely  easy data
    C       structure to generate.  On  the  other hand it   is  not too
    C       efficient on vector computers for  the iterative solution of
    C       linear systems.  Hence,   SLAP changes   this  input    data
    C       structure to the SLAP Column format  for  the iteration (but
    C       does not change it back).
    C
    C       Here is an example of the  SLAP Triad   storage format for a
    C       5x5 Matrix.  Recall that the entries may appear in any order.
    C
    C           5x5 Matrix      SLAP Triad format for 5x5 matrix on left.
    C                              1  2  3  4  5  6  7  8  9 10 11
    C       |11 12  0  0 15|   A: 51 12 11 33 15 53 55 22 35 44 21
    C       |21 22  0  0  0|  IA:  5  1  1  3  1  5  5  2  3  4  2
    C       | 0  0 33  0 35|  JA:  1  2  1  3  5  3  5  2  5  4  1
    C       | 0  0  0 44  0|
    C       |51  0 53  0 55|
    C
    C *Cautions:
    C     This routine will attempt to write to the Fortran logical output
    C     unit IUNIT, if IUNIT .ne. 0.  Thus, the user must make sure that
    C     this logical unit is attached to a file or terminal before calling
    C     this routine with a non-zero value for IUNIT.  This routine does
    C     not check for the validity of a non-zero IUNIT unit number.
    C***REFERENCES  (NONE)
    C***ROUTINES CALLED  (NONE)
    C***REVISION HISTORY  (YYMMDD)
    C   871119  DATE WRITTEN
    C   881213  Previous REVISION DATE
    C   890915  Made changes requested at July 1989 CML Meeting.  (MKS)
    C   890922  Numerous changes to prologue to make closer to SLATEC
    C           standard.  (FNF)
    C   890929  Numerous changes to reduce SP/DP differences.  (FNF)
    C   910411  Prologue converted to Version 4.0 format.  (BAB)
    C   920511  Added complete declaration section.  (WRB)
    C   921007  Changed E's to D's in formats.  (FNF)
    C   930701  Updated CATEGORY section.  (FNF, WRB)
    C***END PROLOGUE  DTOUT