NAG Library Function Document

nag_dge_load (f16qhc)

 Contents

    1  Purpose
    7  Accuracy

1
Purpose

nag_dge_load (f16qhc) initializes a real general matrix.

2
Specification

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

3
Description

nag_dge_load (f16qhc) forms the real m by n general matrix A given by
aij= d if i=j α if ij .  

4
References

Basic Linear Algebra Subprograms Technical (BLAST) Forum (2001) Basic Linear Algebra Subprograms Technical (BLAST) Forum Standard University of Tennessee, Knoxville, Tennessee http://www.netlib.org/blas/blast-forum/blas-report.pdf

5
Arguments

1:     order Nag_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 3.3.1.3 in How to Use the NAG Library and its Documentation for a more detailed explanation of the use of this argument.
Constraint: order=Nag_RowMajor or Nag_ColMajor.
2:     m IntegerInput
On entry: m, the number of rows of the matrix A.
Constraint: m0.
3:     n IntegerInput
On entry: n, the number of columns of the matrix A.
Constraint: n0.
4:     alpha doubleInput
On entry: the value, α, to be assigned to the off-diagonal elements of A.
5:     diag doubleInput
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 when order=Nag_ColMajor;
  • max1,m×pda when order=Nag_RowMajor.
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].
On exit: the m by n general matrix A.
7:     pda IntegerInput
On entry: the stride separating row or column elements (depending on the value of order) in the array a.
Constraints:
  • if order=Nag_ColMajor, pdamax1,m;
  • if order=Nag_RowMajor, pdamax1,n.
8:     fail NagError *Input/Output
The NAG error argument (see Section 3.7 in How to Use the NAG Library and its Documentation).

6
Error Indicators and Warnings

NE_ALLOC_FAIL
Dynamic memory allocation failed.
See Section 2.3.1.2 in How to Use the NAG Library and its Documentation for further information.
NE_BAD_PARAM
On entry, argument value had an illegal value.
NE_INT
On entry, m=value.
Constraint: m0.
On entry, n=value.
Constraint: n0.
NE_INT_2
On entry, pda=value, m=value.
Constraint: pdamax1,m.
On entry, pda=value and n=value.
Constraint: pdamax1,n.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
NE_NO_LICENCE
Your licence key may have expired or may not have been installed correctly.
See Section 2.7.5 in How to Use the NAG Library and its Documentation for further information.

7
Accuracy

The BLAS standard requires accurate implementations which avoid unnecessary over/underflow (see Section 2.7 of Basic Linear Algebra Subprograms Technical (BLAST) Forum (2001)).

8
Parallelism and Performance

nag_dge_load (f16qhc) is not threaded in any implementation.

9
Further Comments

None.

10
Example

This example initializes a real general matrix, A, with diagonal off-diagonal value, α=1.23 and diagonal value, d=3.45.

10.1
Program Text

Program Text (f16qhce.c)

10.2
Program Data

Program Data (f16qhce.d)

10.3
Program Results

Program Results (f16qhce.r)

© The Numerical Algorithms Group Ltd, Oxford, UK. 2017