*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