NAG FL Interface
f06rjf (dlantr)

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FL Specification Language:


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×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 <nag.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)
The routine may be called by the names f06rjf or nagf_blas_dlantr.

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,j|aij| (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 Integer Input
On entry: m, the number of rows of the matrix A.
When m=0, f06rjf is set to zero.
Constraint: m0.
5: n Integer Input
On entry: n, the number of columns of the matrix A.
When n=0, f06rjf is set to zero.
Constraint: n0.
6: a(lda,*) Real (Kind=nag_wp) array Input
Note: the second dimension of the array a must be at least n.
On entry: the m×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 Integer Input
On entry: the first dimension of the array a as declared in the (sub)program from which f06rjf is called.
Constraint: lda max(1,m) .
8: work(*) Real (Kind=nag_wp) array Workspace
Note: the dimension of the array work must be at least max(1,m,n) if norm='I', and at least 1 otherwise.

6 Error Indicators and Warnings

None.

7 Accuracy

Not applicable.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
f06rjf is not threaded in any implementation.

9 Further Comments

None.

10 Example

None.