*DECK STIN
SUBROUTINE STIN (N, NELT, IA, JA, A, ISYM, SOLN, RHS, IUNIT, JOB)
C***BEGIN PROLOGUE STIN
C***PURPOSE Read in SLAP Triad Format Linear System.
C Routine to read in 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 SINGLE PRECISION (STIN-S, DTIN-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 REAL A(NELT), SOLN(N), RHS(N)
C
C CALL STIN( N, NELT, IA, JA, A, ISYM, SOLN, RHS, IUNIT, JOB )
C
C *Arguments:
C N :OUT Integer
C Order of the Matrix.
C NELT :INOUT Integer.
C On input NELT is the maximum number of non-zeros that
C can be stored in the IA, JA, A arrays.
C On output NELT is the number of non-zeros stored in A.
C IA :OUT Integer IA(NELT).
C JA :OUT Integer JA(NELT).
C A :OUT Real A(NELT).
C On output these arrays hold the matrix A in the SLAP
C Triad format. See "Description", below.
C ISYM :OUT 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 :OUT Real SOLN(N).
C The solution to the linear system, if present. This array
C is accessed if and only if JOB to read it in, see below.
C If the user requests that SOLN be read in, but it is not in
C the file, then it is simply zeroed out.
C RHS :OUT Real RHS(N).
C The right hand side vector. This array is accessed if and
C only if JOB is set to read it in, see below.
C If the user requests that RHS be read in, but it is not in
C the file, then it is simply zeroed out.
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 :INOUT Integer.
C Flag indicating what I/O operations to perform.
C On input JOB indicates what Input operations to try to
C perform.
C JOB = 0 => Read only the matrix.
C JOB = 1 => Read matrix and RHS (if present).
C JOB = 2 => Read matrix and SOLN (if present).
C JOB = 3 => Read matrix, RHS and SOLN (if present).
C On output JOB indicates what operations were actually
C performed.
C JOB = 0 => Read in only the matrix.
C JOB = 1 => Read in the matrix and RHS.
C JOB = 2 => Read in the matrix and SOLN.
C JOB = 3 => Read in the matrix, RHS and SOLN.
C
C *Description:
C The format for the input 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,E16.7. 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,E16.7.
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 930701 Updated CATEGORY section. (FNF, WRB)
C***END PROLOGUE STIN
C .. Scalar Arguments ..
INTEGER ISYM, IUNIT, JOB, N, NELT
C .. Array Arguments ..
REAL A(NELT), RHS(N), SOLN(N)
INTEGER IA(NELT), JA(NELT)
C .. Local Scalars ..
INTEGER I, IRHS, ISOLN, JOBRET, NELTMX
C .. Intrinsic Functions ..
INTRINSIC MIN
C***FIRST EXECUTABLE STATEMENT STIN
C
C Read in the information heading.
C
NELTMX = NELT
READ(IUNIT,1000) N, NELT, ISYM, IRHS, ISOLN
NELT = MIN( NELT, NELTMX )
C
C Read in the matrix non-zeros in Triad format.
DO 10 I = 1, NELT
READ(IUNIT,1010) IA(I), JA(I), A(I)
10 CONTINUE
C
C If requested, read in the rhs.
JOBRET = 0
IF( JOB.EQ.1 .OR. JOB.EQ.3 ) THEN
C
C Check to see if rhs is in the file.
IF( IRHS.EQ.1 ) THEN
JOBRET = 1
READ(IUNIT,1020) (RHS(I),I=1,N)
ELSE
DO 20 I = 1, N
RHS(I) = 0
20 CONTINUE
ENDIF
ENDIF
C
C If requested, read in the solution.
IF( JOB.GT.1 ) THEN
C
C Check to see if solution is in the file.
IF( ISOLN.EQ.1 ) THEN
JOBRET = JOBRET + 2
READ(IUNIT,1020) (SOLN(I),I=1,N)
ELSE
DO 30 I = 1, N
SOLN(I) = 0
30 CONTINUE
ENDIF
ENDIF
C
JOB = JOBRET
RETURN
1000 FORMAT(5I10)
1010 FORMAT(1X,I5,1X,I5,1X,E16.7)
1020 FORMAT(1X,E16.7)
C------------- LAST LINE OF STIN FOLLOWS ----------------------------
END