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NAME
     sgbdi - compute the determinant of a  general  matrix  A  in
     banded  storage,  which  has  been  LU-factored  by xGBCO or
     xGBFA.

SYNOPSIS
     SUBROUTINE DGBDI (DA, LDA, N, NSUB, NSUPER, IPIVOT, DDET)

     SUBROUTINE SGBDI (SA, LDA, N, NSUB, NSUPER, IPIVOT, SDET)

     SUBROUTINE ZGBDI (ZA, LDA, N, NSUB, NSUPER, IPIVOT, ZDET)

     SUBROUTINE CGBDI (CA, LDA, N, NSUB, NSUPER, IPIVOT, CDET)



     #include <sunperf.h>

     void dgbdi(double *abd, int lda, int n, int ml, int mu,  int
               *ipivot, double *det) ;

     void sgbdi(float *abd, int lda, int n, int ml, int  mu,  int
               *ipivot, float *det) ;

     void zgbdi(doublecomplex *abd, int lda, int n, int  ml,  int
               mu, int *ipivot, doublecomplex *det) ;

     void cgbdi(complex *abd, int lda, int n, int ml, int mu, int
               *ipivot, complex *det) ;

ARGUMENTS
     xA        LU factorization of the matrix A, as  computed  by
               xGBCO or xGBFA.

     LDA       Leading dimension of the array A as specified in a
               dimension  or  type  statement.  LDA >= 2 * NSUB +
               NSUPER + 1.

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

     NSUB      Number of subdiagonals of A.  N-1 >= NSUB >= 0 but
               if N = 0 then NSUB = 0.

     NSUPER    Number of superdiagonals of A.  N-1 >= NSUPER >= 0
               but if N = 0 then NSUPER = 0.

     IPIVOT    Pivot vector as computed by xGBCO or xGBFA.

     xDET      On exit, the determinant of  the  matrix  A.   The
               determinant  is  stored as b * (10**expon) where b
               is stored in DET(1) and expon is stored in DET(2).
               1.0 <= |DET(1)| <= 10.0  or  DET(1) = 0.0.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER           LDA, N, NDIAG, NSUB, NSUPER
           PARAMETER        (N = 5)
           PARAMETER        (NSUB = 4)
           PARAMETER        (NSUPER = 0)
           PARAMETER        (NDIAG = NSUB + 1 + NSUPER)
           PARAMETER        (LDA = NSUB + NDIAG)
     C
           DOUBLE PRECISION  A(LDA,N), DET(2)
           INTEGER           ICOL, INFO, IPIVOT(N), IROW
     C
           EXTERNAL          DGBDI, DGBFA
     C
     C     Initialize the array A to store the 5x5 matrix A with four
     C     subdiagonals and no superdiagonals shown below.
     C
     C         1
     C         1  -1
     C     A = 1  -2  1
     C         1  -3  3  -1
     C         1  -4  6  -4  1
     C
           DATA A / 4*8D8, 5*1.0D0, 4*8D8, -1.0D0, -2.0D0, -3.0D0, -4.0D0,
          $         5*8D8,1.0D0, 3.0D0, 6.0D0, 6*8D8, -1.0D0, -4.0D0,
          $         7*8D8, 1.0D0, 4*8D8 /
     C
     C     Print the initial values of the arrays.
     C
           PRINT 1000
           PRINT 1010, A(5,1)
           PRINT 1010, A(6,1), A(5,2)
           PRINT 1010, A(7,1), A(6,2), A(5,3)
           PRINT 1010, A(8,1), A(7,2), A(6,3), A(5,4)
           PRINT 1010, A(9,1), A(8,2), A(7,3), A(6,4), A(5,5)
           PRINT 1020
           PRINT 1010, ((A(IROW,ICOL), ICOL = 1, N),
          $              IROW = 1, 2 * NSUB + 1 + NSUPER)
     C
     C     Factor the matrix in banded form.
     C
           CALL DGBFA (A, LDA, N, NSUB, NSUPER, IPIVOT, INFO)
           IF (INFO .EQ. 0) THEN
             CALL DGBDI (A, LDA, N, NSUB, NSUPER, IPIVOT, DET)
             PRINT 1030, DET(1) * (1.0D1 ** DET(2))
           ELSE
             PRINT 1040, INFO
           END IF
     C
      1000 FORMAT (1X, 'A in full form:')
      1010 FORMAT (5(3X, F4.1))
      1020 FORMAT (/1X, 'A in banded form:  (* in unused elements)')
      1030 FORMAT (/1X, 'det(A) = ', F4.1)
      1040 FORMAT (/1X, 'A appears singular at ', I2)
     C
           END

SAMPLE OUTPUT
      A in full form:
         1.0
         1.0   -1.0
         1.0   -2.0    1.0
         1.0   -3.0    3.0   -1.0
         1.0   -4.0    6.0   -4.0    1.0

      A in banded form:  (* in unused elements)
        ****   ****   ****   ****   ****
        ****   ****   ****   ****   ****
        ****   ****   ****   ****   ****
        ****   ****   ****   ****   ****
         1.0   -1.0    1.0   -1.0    1.0
         1.0   -2.0    3.0   -4.0   ****
         1.0   -3.0    6.0   ****   ****
         1.0   -4.0   ****   ****   ****
         1.0   ****   ****   ****   ****

      det(A) =  1.0

Партнёры:

Хостинг: