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NAME
     dgtsl - solve the linear system Ax =  b  for  a  tridiagonal
     matrix A and vectors b and x.

SYNOPSIS
     SUBROUTINE DGTSL (N, DSUBD, DDIAG, DSUPERD, DB, INFO)

     SUBROUTINE SGTSL (N, SSUBD, SDIAG, SSUPERD, SB, INFO)

     SUBROUTINE ZGTSL (N, ZSUBD, ZDIAG, ZSUPERD, ZB, INFO)

     SUBROUTINE CGTSL (N, CSUBD, CDIAG, CSUPERD, BB, INFO)



     #include <sunperf.h>

     void dgtsl(int n, double *dc, double *d, double  *e,  double
               *db, int *info) ;

     void sgtsl(int n, float *sc, float *d, float *e, float  *sb,
               int *info) ;

     void zgtsl(int n, doublecomplex *zc, doublecomplex *d, doub-
               lecomplex *e, doublecomplex *zb, int *info) ;

     void cgtsl(int n, complex *cc, complex *d, complex *e,  com-
               plex *cb, int *info) ;

ARGUMENTS
     N         Order of the matrix A.  N >= 0.

     xSUBD     Subdiagonal of A.  SUBD(2) through SUBD(N) contain
               the subdiagonal and SUBD(1) is not referenced.

     xDIAG     Diagonal of A.

     xSUPERD   Superdiagonal of A.  SUPERD(1) through SUPERD(N-1)
               contain  the  superdiagonal  and  SUPERD(N) is not
               referenced.

     xB        On entry, the right-hand side vector b.  On  exit,
               the solution vector x.

     INFO      On exit:
               INFO = 0  Subroutine completed normally.
               INFO * 0  Returns a value k when the  kth  element
               of the diagonal becomes exactly zero.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE

     C
           INTEGER           N
           PARAMETER        (N = 5)
     C
           DOUBLE PRECISION  B(N), SUBD(N), DIAG(N), SUPERD(N)
           INTEGER           INFO
     C
           EXTERNAL          DGTSL
     C
     C     Initialize the arrays SUBD, DIAG, and SUPERD to store
     C     the subdiagonal, diagonal, and superdiagonal of the
     C     tridiagonal matrix A shown below.  Initialize the array
     C     B to store the right hand side of Ax=b.
     C
     C         -3   1                     6
     C          1  -2   1                12
     C     A =      1  -2   1        b = 18
     C                  1  -2   1        12
     C                      1  -1         6
     C
           DATA SUBD / 8D8, 4*1.0D0 /
           DATA DIAG / -3.0D0, -2.0D0, -2.0D0, -2.0D0, -1.0D0 /
           DATA SUPERD / 4*1.0D0, 8D8 /
           DATA B / 6.0D0, 1.2D1, 1.8D1, 1.2D1, 6.0D0 /
     C
           PRINT 1000
           PRINT 1010, DIAG(1), SUPERD(1)
           PRINT 1020, SUBD(2), DIAG(2), SUPERD(2)
           PRINT 1030, SUBD(3), DIAG(3), SUPERD(3)
           PRINT 1040, SUBD(4), DIAG(4), SUPERD(4)
           PRINT 1050, SUBD(5), DIAG(5)
           PRINT 1060
           PRINT 1070, B
           CALL DGTSL (N, SUBD, DIAG, SUPERD, B, INFO)
           IF (INFO .EQ. 0) THEN
             PRINT 1080
             PRINT 1070, B
           ELSE
             PRINT 1090, INFO
           END IF
     C
      1000 FORMAT (1X, 'A:')
      1010 FORMAT (1X, 2(2X, F4.1))
      1020 FORMAT (1X, 3(2X, F4.1))
      1030 FORMAT (1X, 6X, 3(2X, F4.1))
      1040 FORMAT (1X, 12X, 3(2X, F4.1))
      1050 FORMAT (1X, 18X, 2(2X, F4.1))
      1060 FORMAT (/1X, 'b:')
      1070 FORMAT (3X, F6.1)
      1080 FORMAT (/1X, 'A**(-1) * b:')
      1090 FORMAT (/1X, 'A appears singular at ', I1)
     C
           END

SAMPLE OUTPUT
      A:
        -3.0   1.0
         1.0  -2.0   1.0
               1.0  -2.0   1.0
                     1.0  -2.0   1.0
                           1.0  -1.0

      b:
           6.0
          12.0
          18.0
          12.0
           6.0

      A**(-1) * b:
         -27.0
         -75.0
        -111.0
        -129.0
        -135.0

Партнёры:

Хостинг: