CSFRG

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