NAG Library Routine Document

f06rjf (dlantr)

1
Purpose

f06rjf returns, via the function name, the value of the 1-norm, the -norm, the Frobenius norm, or the maximum absolute value of the elements of a real m by n trapezoidal matrix (triangular if m=n).

2
Specification

Fortran Interface
Function f06rjf ( norm, uplo, diag, m, n, a, lda, work)
Real (Kind=nag_wp):: f06rjf
Integer, Intent (In):: m, n, lda
Real (Kind=nag_wp), Intent (In):: a(lda,*)
Real (Kind=nag_wp), Intent (Inout):: work(*)
Character (1), Intent (In):: norm, uplo, diag
C Header Interface
#include <nagmk26.h>
double  f06rjf_ (const char *norm, const char *uplo, const char *diag, const Integer *m, const Integer *n, const double a[], const Integer *lda, double work[], const Charlen length_norm, const Charlen length_uplo, const Charlen length_diag)

3
Description

None.

4
References

None.

5
Arguments

1:     norm – Character(1)Input
On entry: specifies the value to be returned.
norm='1' or 'O'
The 1-norm.
norm='I'
The -norm.
norm='F' or 'E'
The Frobenius (or Euclidean) norm.
norm='M'
The value maxi,jaij (not a norm).
Constraint: norm='1', 'O', 'I', 'F', 'E' or 'M'.
2:     uplo – Character(1)Input
On entry: specifies whether A is upper or lower trapezoidal.
uplo='U'
A is upper trapezoidal.
uplo='L'
A is lower trapezoidal.
Constraint: uplo='U' or 'L'.
3:     diag – Character(1)Input
On entry: specifies whether A has nonunit or unit diagonal elements.
diag='N'
The diagonal elements are stored explicitly.
diag='U'
The diagonal elements are assumed to be 1, and are not referenced.
Constraint: diag='N' or 'U'.
4:     m – IntegerInput
On entry: m, the number of rows of the matrix A.
When m=0, f06rjf is set to zero.
Constraint: m0.
5:     n – IntegerInput
On entry: n, the number of columns of the matrix A.
When n=0, f06rjf is set to zero.
Constraint: n0.
6:     alda* – Real (Kind=nag_wp) arrayInput
Note: the second dimension of the array a must be at least n.
On entry: the m by n trapezoidal matrix A.
  • If uplo='U', A is upper trapezoidal and the elements of the array below the diagonal are not referenced.
  • If uplo='L', A is lower trapezoidal and the elements of the array above the diagonal are not referenced.
  • If diag='U', the diagonal elements of A are assumed to be 1, and are not referenced.
7:     lda – IntegerInput
On entry: the first dimension of the array a as declared in the (sub)program from which f06rjf is called.
Constraint: lda max1,m .
8:     work* – Real (Kind=nag_wp) arrayWorkspace
Note: the dimension of the array work must be at least max1,m,n  if norm='I', and at least 1 otherwise.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06rjf is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.