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NAME
     dgesl - solve the linear system Ax = b for a general  matrix
     A,  which  has been LU- factored by xGECO or xGEFA, and vec-
     tors b and x.

SYNOPSIS
     SUBROUTINE DGESL (DA, LDA, N, IPIVOT, DB, JOB)

     SUBROUTINE SGESL (SA, LDA, N, IPIVOT, SB, JOB)

     SUBROUTINE ZGESL (ZA, LDA, N, IPIVOT, ZB, JOB)

     SUBROUTINE CGESL (CA, LDA, N, IPIVOT, CB, JOB)



     #include <sunperf.h>

     void dgesl(double *da, int lda, int n, int  *ipivot,  double
               *db, int job);

     void sgesl(float *sa, int lda, int n, int *ipivot, float *b,
               int job);

     void zgesl(doublecomplex *za, int lda, int n,  int  *ipivot,
               doublecomplex *zb, int job);

     void cgesl(complex *ca, int lda, int n, int *ipivot, complex
               *cb, int job);

ARGUMENTS
     xA        LU factorization of the matrix A, as  computed  by
               xGECO or xGEFA.

     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.

     IPIVOT    Pivot vector as computed by xGECO or xGEFA.

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

     JOB       Determines which  operation  the  subroutine  will
               perform:
                    0    Solve the system Ax = b.
                    not 0     Solve the linear system  AHx  =  b.
               Note that ATx = AHx for real matrices.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER           IAXEQB, LDA, LDB, N
           PARAMETER        (IAXEQB = 0)
           PARAMETER        (N = 3)
           PARAMETER        (LDA = N)
           PARAMETER        (LDB = LDA)
     C
           DOUBLE PRECISION  A(LDA,N), B(LDB)
           INTEGER           ICOL, INFO, IPIVOT(N), IROW, JOB
     C
           EXTERNAL          DGEFA, DGESL
     C
     C     Initialize the array A to store the matrix A shown below.
     C     Initialize the array B to store the vector b shown below.
     C
     C         1  2  2        15
     C     A = 2  1  2    b = 15
     C         2  2  1        15
     C
           DATA A / 1.0D0, 3*2.0D0, 1.0D0, 3*2.0D0, 1.0D0 /
           DATA B / 3*1.5D1 /
     C
           PRINT 1000
           PRINT 1010, ((A(IROW,ICOL), ICOL = 1, N), IROW = 1, N)
           PRINT 1020
           PRINT 1030, B
           CALL DGEFA (A, LDA, N, IPIVOT, INFO)
           IF (INFO .EQ. 0) THEN
             JOB = IAXEQB
             CALL DGESL (A, LDA, N, IPIVOT, B, JOB)
             PRINT 1040
             PRINT 1030, B
           ELSE
             PRINT 1050, INFO
           END IF
     C
      1000 FORMAT (1X, 'A:')
      1010 FORMAT (3(3X, F4.1))
      1020 FORMAT (/1X, 'b:')
      1030 FORMAT (1X, 2X, F4.1)
      1040 FORMAT (/1X, 'A**(-1)*b')
      1050 FORMAT (1X, 'A appears singular at ', I2)
     C
           END

SAMPLE OUTPUT
      A:
         1.0    2.0    2.0
         2.0    1.0    2.0
         2.0    2.0    1.0

      b:
        15.0
        15.0
        15.0

      A**(-1)*b
         3.0
         3.0
         3.0

Партнёры:

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