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NAME
     dtrco - estimate the condition number of a triangular matrix
     A.   It  is typical to follow a call to xTRCO with a call to
     xTRSL to solve Ax = b or to xTRDI to compute the determinant
     and inverse of A.

SYNOPSIS
     SUBROUTINE DTRCO (DA, LDA, N, DRCOND, DWORK, JOB)

     SUBROUTINE STRCO (SA, LDA, N, SRCOND, SWORK, JOB)

     SUBROUTINE ZTRCO (ZA, LDA, N, DRCOND, ZWORK, JOB)

     SUBROUTINE CTRCO (CA, LDA, N, SRCOND, CWORK, JOB)



     #include <sunperf.h>

     void dtrco(double *t, int ldt, int n,  double  *drcond,  int
               job);

     void strco(float *t, int ldt,  int  n,  float  *srcond,  int
               job);

     void ztrco(doublecomplex *t, int ldt, int n, double *drcond,
               int job);

     void ctrco(complex *t, int ldt, int n,  float  *srcond,  int
               job);

ARGUMENTS
     xA        Matrix A.

     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.

     xRCOND    On exit, an estimate of the  reciprocal  condition
               number  of  A.  0.0 <= RCOND <= 1.0.  As the value
               of RCOND gets smaller, operations with A  such  as
               solving  Ax  = b may become less stable.  If RCOND
               satisfies RCOND + 1.0 = 1.0 then A may be singular
               to working precision.

     xWORK     Scratch array with a dimension of N.

     JOB       If JOB = 0, then A is lower triangular;  otherwise
               A is upper triangular.


SAMPLE PROGRAM
           PROGRAM TEST
           IMPLICIT NONE
     C
           INTEGER           ILOWER, LDA, N
           PARAMETER        (ILOWER = 0)
           PARAMETER        (N = 5)
           PARAMETER        (LDA = N)
     C
           DOUBLE PRECISION  A(LDA,N), RCOND, WORK(N)
           INTEGER           ICOL, IROW, JOB
     C
           EXTERNAL          DTRCO
     C
     C     Initialize the array A to store the 5x5 triangular matrix A
     C     shown below.
     C
     C         1
     C         1  1
     C     A = 1  1  1
     C         1  1  1  1
     C         1  1  1  1  1
     C
           DATA A / 5*1.0D0, 8D8, 4*1.0D0, 2*8D8, 3*1.0D0, 3*8D8,
          $         2*1.0D0, 4*8D8, 1.0D0 /
     C
     C     Print the initial values of the arrays.
     C
           PRINT 1000
           DO 100, IROW = 1, N
             PRINT 1010, (A(IROW,ICOL), ICOL = 1, IROW)
       100 CONTINUE
           PRINT 1020
           PRINT 1010, ((A(IROW,ICOL), ICOL = 1, N), IROW = 1, LDA)
     C
     C     Estimate the condition number of the matrix.
     C
           JOB = ILOWER
           CALL DTRCO (A, LDA, N, RCOND, WORK, JOB)
           PRINT 1030, RCOND
     C
      1000 FORMAT (1X, 'A in full form:')
      1010 FORMAT (5(3X, F4.1))
      1020 FORMAT (/1X, 'A in triangular form:  (* in unused elements)')
      1030 FORMAT (/1X, 'Reciprocal of the condition number:', F4.1)
     C
           END

SAMPLE OUTPUT
      A in full form:
         1.0
         1.0    1.0
         1.0    1.0    1.0
         1.0    1.0    1.0    1.0
         1.0    1.0    1.0    1.0    1.0

      A in triangular form:  (* in unused elements)
         1.0   ****   ****   ****   ****
         1.0    1.0   ****   ****   ****
         1.0    1.0    1.0   ****   ****
         1.0    1.0    1.0    1.0   ****
         1.0    1.0    1.0    1.0    1.0

      Reciprocal of the condition number: 0.1

Партнёры:

Хостинг: