[n,nelt,ia,ja,a,isym,soln,rhs,iunit,job]=dtin(n,nelt,ia,ja,a,isym,soln,rhs,iunit,job);

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

if isempty(i), i=0; end;
if isempty(irhs), irhs=0; end;
if isempty(isoln), isoln=0; end;
if isempty(jobret), jobret=0; end;
if isempty(neltmx), neltmx=0; end;
%     .. Intrinsic Functions ..
%***FIRST EXECUTABLE STATEMENT  DTIN
%
%         Read in the information heading.
%
neltmx = fix(nelt);
[ n , nelt , isym , irhs , isoln]=readf(iunit,[repmat('%10u',1,5)],1);
%format(5i10);
nelt = fix(min(nelt,neltmx));
%
%         Read in the matrix non-zeros in Triad format.
for i = 1 : nelt;
[ ia(i) , ja(i) , a(i)]=readf(iunit,[repmat(' ',1,1),'%5u',repmat(' ',1,1),'%5u',repmat(' ',1,1),'%16.7f'],3);
%format(1x,i5,1x,i5,1x,d16.7);
end; i = fix(nelt+1);
%
%         If requested, read in the rhs.
jobret = 0;
if( job==1 || job==3 )
%
%         Check to see if rhs is in the file.
if( irhs==1 )
jobret = 1;
[rhs([1:n])]=readf(iunit,[repmat(' ',1,1),'%16.7f'],1);
else;
for i = 1 : n;
rhs(i) = 0;
end; i = fix(n+1);
end;
end;
%
%         If requested, read in the solution.
if( job>1 )
%
%         Check to see if solution is in the file.
if( isoln==1 )
jobret = fix(jobret + 2);
[soln([1:n])]=readf(iunit,[repmat(' ',1,1),'%16.7f'],1);
else;
for i = 1 : n;
soln(i) = 0;
end; i = fix(n+1);
end;
end;
%
job = fix(jobret);
return;
%format(1x,d16.7);
%------------- LAST LINE OF DTIN FOLLOWS ----------------------------
end
%DECK DTOUT