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dtrco (3)
  • >> dtrco (3) ( Solaris man: Библиотечные вызовы )
  • 
    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
    
    
    
    


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