NRIRR

Computes the infinity norm of a real matrix.

Required Arguments

A — Real NRA by NCA matrix whose infinity norm is to be computed. (Input)

ANORM — Real scalar containing the infinity norm of A. (Output)

NRA — Number of rows of A. (Input)
Default: NRA = SIZE (A,1).

NCA — Number of columns of A. (Input)
Default: NCA = 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).

Generic: CALL NRIRR (A, ANORM [, …])

Specific: The specific interface names are S_NRIRR and D_NRIRR.

Single: CALL NRIRR (NRA, NCA, A, LDA, ANORM)

Double: The double precision name is DNRIRR.

The routine NRIRR computes the infinity norm of a real rectangular matrix A. If m = NRA and n = NCA, then the ∞-norm of A is

This is the maximum of the sums of the absolute values of the row elements.

Compute the infinity norm of a 3 × 4 real rectangular matrix.

USE NRIRR_INT

USE UMACH_INT

IMPLICIT NONE

! Declare variables

INTEGER NCA, NRA

PARAMETER (NCA=4, NRA=3)

INTEGER NOUT

REAL A(NRA,NCA), ANORM

! Set values for A

! A = ( 1.0 0.0 2.0 0.0 )

! ( 3.0 4.0 -1.0 0.0 )

! ( 2.0 1.0 2.0 1.0 )

DATA A/1.0, 3.0, 2.0, 0.0, 4.0, 1.0, 2.0, -1.0, 2.0, 0.0, 0.0, &

1.0/

! Compute the infinity norm of A

CALL NRIRR (A, ANORM)

! Print results

CALL UMACH (2, NOUT)

WRITE (NOUT,*) ' The infinity norm of A is ', ANORM

END

Output

The infinity norm of A is 8.00000