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NAME
     zspfa - compute the UDU factorization of a symmetric  matrix
     A  in  packed  storage.   It  is typical to follow a call to
     xSPFA with a call to xSPSL to solve Ax = b or  to  xSPDI  to
     compute the determinant, inverse, and inertia of A.

SYNOPSIS
     SUBROUTINE DSPFA (DA, N, IPIVOT, INFO)

     SUBROUTINE SSPFA (SA, N, IPIVOT, INFO)

     SUBROUTINE ZSPFA (ZA, N, IPIVOT, INFO)

     SUBROUTINE CSPFA (CA, N, IPIVOT, INFO)



     #include <sunperf.h>

     void dspfa(double *dap, int n, int *kpvt, int *info);

     void sspfa(float *sap, int n, int *kpvt, int *info);

     void zspfa(doublecomplex *zap, int n, int *kpvt, int *info);

     void cspfa(complex *cap, int n, int *kpvt, int *info);

ARGUMENTS
     xA        On entry, the upper triangle of the matrix A.   On
               exit, a UDU factorization of the matrix A.

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

     IPIVOT    On exit, a vector of pivot indices.

     INFO      On exit:
               INFO = 0  Subroutine completed normally.
               INFO > 0  Returns a value k if the kth pivot block
               is  singular  to indicate that xSPSL or xSPDI will
               divide by zero if called.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER           IDODET, IDOINR, IDOINV, JOB, LENGTA, N
           PARAMETER        (IDODET = 10)
           PARAMETER        (IDOINR = 100)
           PARAMETER        (IDOINV = 1)
           PARAMETER        (JOB = 111)
           PARAMETER        (N = 3)
           PARAMETER        (LENGTA = (N * N + N) / 2)

     C
           DOUBLE PRECISION  A(LENGTA), DET(2), WORK(N)
           INTEGER           INERT(3), INFO, IPIVOT(N)
     C
           EXTERNAL          DSPDI, DSPFA
     C
     C     Initialize the array A to store in packed symmetric format
     C     the matrix A shown below.
     C
     C         3  2  1
     C     A = 2  2  1
     C         1  1  1
     C
           DATA A / 3.0D0, 2.0D0, 2.0D0, 1.0D0, 1.0D0, 1.0D0 /
     C
           PRINT 1000
           PRINT 1010, A(1), A(2), A(4)
           PRINT 1010, A(2), A(3), A(5)
           PRINT 1010, A(4), A(5), A(6)
           CALL DSPFA (A, N, IPIVOT, INFO)
           IF (INFO .EQ. 0) THEN
             CALL DSPDI (A, N, IPIVOT, DET, INERT, WORK, JOB)
             PRINT 1020, DET(1) * (10.0D0 ** DET(2))
             PRINT 1030, INERT
             PRINT 1040
             PRINT 1010, A(1), A(2), A(4)
             PRINT 1010, A(2), A(3), A(5)
             PRINT 1010, A(4), A(5), A(6)
           ELSE
             PRINT 1050
           END IF
     C
      1000 FORMAT (1X, 'A:')
      1010 FORMAT (3(3X, F5.2))
      1020 FORMAT (/1X, 'Determinant of A: ', F7.3)
      1030 FORMAT (1X, 'Inertia of A: <', I1, ',', I1, ',', I1, '>')
      1040 FORMAT (/1X, 'A**(-1):')
      1050 FORMAT (1X, 'A is too ill-conditioned.')
     C
           END

SAMPLE OUTPUT
      A:
         3.00    2.00    1.00
         2.00    2.00    1.00
         1.00    1.00    1.00

      Determinant of A:   1.000
      Inertia of A: <3,0,0>

      A**(-1):
         1.00   -1.00    0.00

        -1.00    2.00   -1.00
         0.00   -1.00    2.00

Партнёры:

Хостинг: