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NAME
     spofa - compute a  Cholesky  factorization  of  a  symmetric
     positive  definite matrix A.  It is typical to follow a call
     to xPOFA with a call to xPOSL to solve Ax = b or to xPODI to
     compute the determinant and inverse of A.

SYNOPSIS
     SUBROUTINE DPOFA (DA, LDA, N, INFO)

     SUBROUTINE SPOFA (SA, LDA, N, INFO)

     SUBROUTINE ZPOFA (ZA, LDA, N, INFO)

     SUBROUTINE CPOFA (CA, LDA, N, INFO)



     #include <sunperf.h>

     void dpofa(double *da, int lda, int n, int *info) ;

     void spofa(float *sa, int lda, int n, int *info) ;

     void cpofa(complex *ca, int lda, int n, int *info) ;

     void zpofa(doublecomplex *za, int lda, int n, int *info) ;

ARGUMENTS
     xA        On entry, the upper triangle of the matrix A.   On
               exit,  a  Cholesky  factorization of the matrix A.
               The strict lower triangle of A is not referenced.

     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.

     INFO      On exit:
               INFO = 0  Subroutine completed normally.
               INFO > 0  Returns a value k if the  leading  minor
               of order k is not positive definite.

SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER           LDA, N
           PARAMETER        (N = 5)
           PARAMETER        (LDA = N)
     C
           DOUBLE PRECISION  A(LDA,N), B(N)
           INTEGER           ICOL, INFO, IROW

     C
           EXTERNAL          DPOFA, DPOSL
     C
     C     Initialize the array A to store in symmetric storage mode the
     C     matrix A shown below.  Initialize the array B to store the vector
     C     B shown below.
     C
     C          5  4  3  2  1        120
     C          4  5  4  3  2         60
     C     A =  3  4  5  4  3    b =  40
     C          2  3  4  5  4         60
     C          1  2  3  4  5        120
     C
           DATA A / 5.0D0, 4*8D8, 4.0D0, 5.0D0, 3*8D8, 3.0D0, 4.0D0, 5.0D0,
          $         2*8D8, 2.0D0, 3.0D0, 4.0D0, 5.0D0, 1*8D8, 1.0D0, 2.0D0,
          $         3.0D0, 4.0D0, 5.0D0 /
           DATA B / 1.2D2, 6.0D1, 4.0D1, 6.0D1, 1.2D2 /
     C
           PRINT 1000
           DO 100, IROW = 1, N
             PRINT 1010, (A(ICOL,IROW), ICOL = 1, IROW),
          $              (A(IROW,ICOL), ICOL = IROW + 1, N)
       100 CONTINUE
           PRINT 1020
           PRINT 1010, ((A(IROW,ICOL), ICOL = 1, N), IROW = 1, N)
           PRINT 1030
           PRINT 1040, B
           CALL DPOFA (A, LDA, N, INFO)
           IF (INFO .EQ. 0) THEN
             CALL DPOSL (A, LDA, N, B)
             PRINT 1050
             PRINT 1040, B
           ELSE
             PRINT 1060
           END IF
     C
      1000 FORMAT (1X, 'A in full form:')
      1010 FORMAT (5(3X, F7.3))
      1020 FORMAT (/1X, 'A in symmetric form:  (* in unused entries)')
      1030 FORMAT (/1X, 'b:')
      1040 FORMAT (3X, F7.3)
      1050 FORMAT (/1X, 'A**(-1) * b:')
      1060 FORMAT (/1X, 'A is not positive definite.')
     C
           END

SAMPLE OUTPUT
      A in full form:
          5.000     4.000     3.000     2.000     1.000
          4.000     5.000     4.000     3.000     2.000
          3.000     4.000     5.000     4.000     3.000
          2.000     3.000     4.000     5.000     4.000
          1.000     2.000     3.000     4.000     5.000

      A in symmetric form:  (* in unused entries)
          5.000     4.000     3.000     2.000     1.000
        *******     5.000     4.000     3.000     2.000
        *******   *******     5.000     4.000     3.000
        *******   *******   *******     5.000     4.000
        *******   *******   *******   *******     5.000

      b:
        120.000
         60.000
         40.000
         60.000
        120.000

      A**(-1) * b:
         50.000
        -20.000
        -20.000
        -20.000
         50.000

Партнёры:

Хостинг: