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NAME
     sppdi - compute the determinant and inverse of  a  symmetric
     positive definite matrix A in packed storage, which has been
     Cholesky-factored by xPPCO or xPPFA.

SYNOPSIS
     SUBROUTINE DPPDI (DA, N, DDET, JOB)

     SUBROUTINE SPPDI (SA, N, SDET, JOB)

     SUBROUTINE ZPPDI (ZA, N, DDET, JOB)

     SUBROUTINE CPPDI (CA, N, SDET, JOB)



     #include <sunperf.h>

     void dppdi(double *dap, int n, double *det, int job);

     void sppdi(float *sap, int n, float *det, int job);

     void zppdi(doublecomplex *zap, int n, double *det, int job);

     void cppdi(complex *cap, int n, float *det, int job);

ARGUMENTS
     xA        On entry, the Cholesky factorization of the matrix
               A,  as  computed  by xPPCO or xPPFA.  On exit, the
               inverse of the original matrix A  if  the  inverse
               was  requested,  otherwise  A  is  unchanged.  The
               strict lower triangle of A is not referenced.

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

     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.

     JOB       Determines which  operation  the  subroutine  will
               perform:
                    11   both determinant and inverse
                    01   inverse only
                    10   determinant only

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER           INVDET, LENGTA, N
           PARAMETER        (INVDET = 11)
           PARAMETER        (N = 4)
           PARAMETER        (LENGTA = (N * N + N) / 2)
     C
           DOUBLE PRECISION  A(LENGTA), DET(2)
           INTEGER           INFO, JOB
     C
           EXTERNAL          DPPFA, DPPDI
     C
     C     Initialize the array A to store in packed symmetric storage
     C     mode the matrix A shown below.  Initialize the array B to store
     C     the vector B shown below.
     C
     C         4  3  2  1
     C     A = 3  4  3  2
     C         2  3  4  3
     C         1  2  3  4
     C
           DATA A / 4.0D0, 3.0D0, 4.0D0, 2.0D0, 3.0D0, 4.0D0,
          $         1.0D0, 2.0D0, 3.0D0, 4.0D0 /
     C
           PRINT 1000
           PRINT 1010, A(1), A(2), A(4), A(7)
           PRINT 1010, A(2), A(3), A(5), A(8)
           PRINT 1010, A(4), A(5), A(6), A(9)
           PRINT 1010, A(7), A(8), A(9), A(10)
           CALL DPPFA (A, N, INFO)
           IF (INFO .EQ. 0) THEN
             JOB = INVDET
             CALL DPPDI (A, N, DET, JOB)
             PRINT 1020, DET(1) * (1.0D1 ** DET(2))
             PRINT 1030
             PRINT 1010, A(1), A(2), A(4), A(7)
             PRINT 1010, A(2), A(3), A(5), A(8)
             PRINT 1010, A(4), A(5), A(6), A(9)
             PRINT 1010, A(7), A(8), A(9), A(10)
           ELSE
             PRINT 1040
           END IF
     C
      1000 FORMAT (1X, 'A in full form:')
      1010 FORMAT (4(3X, F5.1))
      1020 FORMAT (/1X, 'Determinant of A is ', F4.1)
      1030 FORMAT (/1X, 'A**(-1):')
      1040 FORMAT (/1X, 'A is too ill-conditioned.')
     C
           END

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

      Determinant of A is 20.0

      A**(-1):
          0.6    -0.5     0.0     0.1
         -0.5     1.0    -0.5     0.0
          0.0    -0.5     1.0    -0.5
          0.1     0.0    -0.5     0.6

Партнёры:

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