Extends a real symmetric matrix defined in its upper triangle to its lower triangle.

Required Arguments

A — N by N symmetric matrix of order N to be filled out.   (Input/Output)

Optional Arguments

N — Order of the matrix A.   (Input)
Default: N = size (A,2).

LDA — Leading dimension of A exactly as specified in the dimension statement of the calling program.   (Input)
Default: LDA = size (A,1).

FORTRAN 90 Interface

Generic:          CALL CSFRG (A [,…])

Specific:          The specific interface names are S_CSFRG and D_CSFRG.

FORTRAN 77 Interface

Single:            CALL CSFRG (N, A, LDA)

Double:          The double precision name is DCSFRG.

Description

The routine CSFRG converts an N ´ N matrix A in symmetric mode into a general matrix by filling in the lower triangular portion of A using the values defined in its upper triangular portion.

Example

The lower triangular portion of a real 3 ´ 3 symmetric matrix is filled with the values defined in its upper triangular portion.

 

      USE CSFRG_INT

      USE WRRRN_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    LDA, N

      PARAMETER  (LDA=3, N=3)

!

      REAL       A(LDA,N)

!                                 Set values for  A

!                                 A = (   0.0   3.0   4.0  )

!                                     (         1.0   5.0  )

!                                     (               2.0  )

!

      DATA A/3*0.0, 3.0, 1.0, 0.0, 4.0, 5.0, 2.0/

!                                 Fill the lower portion of A

      CALL CSFRG (A)

!                                 Print results

      CALL WRRRN ('A', A)

      END

Output

 

            A
        1       2       3
1   0.000   3.000   4.000
2   3.000   1.000   5.000
3   4.000   5.000   2.000

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