nag_dtr_load (f16qgc) (PDF version)
f16 Chapter Contents
f16 Chapter Introduction
NAG C Library Manual

NAG Library Function Document

nag_dtr_load (f16qgc)

+ Contents

    1  Purpose
    7  Accuracy

1  Purpose

nag_dtr_load (f16qgc) initializes a real triangular matrix.

2  Specification

#include <nag.h>
#include <nagf16.h>
void  nag_dtr_load (Nag_OrderType order, Nag_UploType uplo, Integer n, double alpha, double diag, double a[], Integer pda, NagError *fail)

3  Description

nag_dtr_load (f16qgc) forms the real n by n triangular matrix A given by
aij= d if i=j α if ij .

4  References

The BLAS Technical Forum Standard (2001) http://www.netlib.org/blas/blast-forum

5  Arguments

1:     orderNag_OrderTypeInput
On entry: the order argument specifies the two-dimensional storage scheme being used, i.e., row-major ordering or column-major ordering. C language defined storage is specified by order=Nag_RowMajor. See Section 3.2.1.3 in the Essential Introduction for a more detailed explanation of the use of this argument.
Constraint: order=Nag_RowMajor or Nag_ColMajor.
2:     uploNag_UploTypeInput
On entry: specifies whether the upper or lower triangular part of A is stored.
uplo=Nag_Upper
The upper triangular part of A is stored.
uplo=Nag_Lower
The lower triangular part of A is stored.
Constraint: uplo=Nag_Upper or Nag_Lower.
3:     nIntegerInput
On entry: n, the order of the matrix A.
Constraint: n0.
4:     alphadoubleInput
On entry: the value, α, to be assigned to the off-diagonal elements of A.
5:     diagdoubleInput
On entry: the value, d, to be assigned to the diagonal elements of A.
6:     a[dim]doubleOutput
Note: the dimension, dim, of the array a must be at least max1,pda×n.
On exit: the n by n triangular matrix A.
If order=Nag_ColMajor, Aij is stored in a[j-1×pda+i-1].
If order=Nag_RowMajor, Aij is stored in a[i-1×pda+j-1].
  • If uplo=Nag_Upper, A is upper triangular and the elements of the array corresponding to the lower triangular part of A are not referenced.
  • If uplo=Nag_Lower, A is lower triangular and the elements of the array corresponding to the upper triangular part of A are not referenced.
7:     pdaIntegerInput
On entry: the stride separating row or column elements (depending on the value of order) of the matrix A in the array a.
Constraint: pdamax1,n.
8:     failNagError *Input/Output
The NAG error argument (see Section 3.6 in the Essential Introduction).

6  Error Indicators and Warnings

NE_ALLOC_FAIL
Dynamic memory allocation failed.
NE_BAD_PARAM
On entry, argument value had an illegal value.
NE_INT
On entry, n=value.
Constraint: n0.
NE_INT_2
On entry, pda=value, n=value.
Constraint: pdamax1,n.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

This example initializes the lower triangular matrix A with diagonal elements given by d=3.45 and off-diagonal elements given by α=1.23.

9.1  Program Text

Program Text (f16qgce.c)

9.2  Program Data

Program Data (f16qgce.d)

9.3  Program Results

Program Results (f16qgce.r)


nag_dtr_load (f16qgc) (PDF version)
f16 Chapter Contents
f16 Chapter Introduction
NAG C Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012