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

SYNOPSIS
     SUBROUTINE DTRSL (DA, LDA, N, DB, JOB, INFO)

     SUBROUTINE STRSL (SA, LDA, N, SB, JOB, INFO)

     SUBROUTINE ZTRSL (ZA, LDA, N, ZB, JOB, INFO)

     SUBROUTINE CTRSL (CA, LDA, N, CB, JOB, INFO)



     #include <sunperf.h>

     void dtrsl(double *t, int ldt, int n, double *db,  int  job,
               int *info) ;

     void strsl(float *t, int ldt, int n, float *sb, int job, int
               *info) ;

     void ztrsl(doublecomplex *t, int ldt, int  n,  doublecomplex
               *zb, int job, int *info) ;

     void ctrsl(complex *t, int ldt, int n, complex *cb, int job,
               int *info) ;

ARGUMENTS
     xA        Matrix A.

     LDA       Leading dimension of the array A as specified in a
               dimension or type statement.  LDA >= max(1,N).

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

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

     JOB       Determines which  operation  the  subroutine  will
               perform:
                    00   Solve Ax = b, A lower triangular.
                    01   Solve Ax = b, A upper triangular.
                    10   Solve AHx = b, A lower triangular.
                    11   Solve AHx = b, A upper triangular.  Note
               that ATx = AHx for real matrices.

     INFO      On exit:
               INFO = 0  Subroutine completed normally.
               INFO * 0  Returns the  index  of  the  first  zero
               diagonal element of A.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER           LDA, LOTRAN, N
           PARAMETER        (LOTRAN = 10)
           PARAMETER        (N = 5)
           PARAMETER        (LDA = N)
     C
           DOUBLE PRECISION  A(LDA,N), B(N)
           INTEGER           ICOL, INFO, IROW, JOB
     C
           EXTERNAL          DTRSL
     C
     C     Initialize the array A to store the 5x5 triangular matrix A
     C     shown below.
     C
     C         1                    5
     C         1  1                 4
     C     A = 1  1  1          b = 3
     C         1  1  1  1           2
     C         1  1  1  1  1        1
     C
           DATA A / 5*1.0D0, 8D8, 4*1.0D0, 2*8D8, 3*1.0D0, 3*8D8,
          $         2*1.0D0, 4*8D8, 1.0D0 /
           DATA B / 5.0D0, 4.0D0, 3.0D0, 2.0D0, 1.0D0 /
     C
     C     Print the initial values of the arrays.
     C
           PRINT 1000
           DO 100, IROW = 1, N
             PRINT 1010, (A(IROW,ICOL), ICOL = 1, IROW)
       100 CONTINUE
           PRINT 1020
           PRINT 1010, ((A(IROW,ICOL), ICOL = 1, N), IROW = 1, LDA)
           PRINT 1030
           PRINT 1040, B
     C
     C     Solve the matrix in banded form.
     C
           JOB = LOTRAN
           CALL DTRSL (A, LDA, N, B, JOB, INFO)
           IF (INFO .EQ. 0) THEN
             PRINT 1050
             PRINT 1040, B
           ELSE
             PRINT 1060, INFO
           END IF
     C
      1000 FORMAT (1X, 'A in full form:')
      1010 FORMAT (5(3X, F4.1))
      1020 FORMAT (/1X, 'A in triangular form:  (* in unused elements)')
      1030 FORMAT (/1X, 'b:')
      1040 FORMAT (3X, F4.1)
      1050 FORMAT (/1X, 'A''**(-1) * b:')
      1060 FORMAT (1X, 'A appears singular at ', I2)
     C
           END

SAMPLE OUTPUT
      A in full form:
         1.0
         1.0    1.0
         1.0    1.0    1.0
         1.0    1.0    1.0    1.0
         1.0    1.0    1.0    1.0    1.0

      A in triangular form:  (* in unused elements)
         1.0   ****   ****   ****   ****
         1.0    1.0   ****   ****   ****
         1.0    1.0    1.0   ****   ****
         1.0    1.0    1.0    1.0   ****
         1.0    1.0    1.0    1.0    1.0

      b:
         5.0
         4.0
         3.0
         2.0
         1.0

      A'**(-1) * b:
         1.0
         1.0
         1.0
         1.0
         1.0

Партнёры:

Хостинг: