NAG Library Routine Document

f06pmf  (dger)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06pmf (dger) computes the rank-1 update of a real general matrix.

2
Specification

Fortran Interface
Subroutine f06pmf ( m, n, alpha, x, incx, y, incy, a, lda)
Integer, Intent (In):: m, n, incx, incy, lda
Real (Kind=nag_wp), Intent (In):: alpha, x(*), y(*)
Real (Kind=nag_wp), Intent (Inout):: a(lda,*)
C Header Interface
#include nagmk26.h
void  f06pmf_ ( const Integer *m, const Integer *n, const double *alpha, const double x[], const Integer *incx, const double y[], const Integer *incy, double a[], const Integer *lda)
The routine may be called by its BLAS name dger.

3
Description

f06pmf (dger) performs the rank-1 update operation
AαxyT + A ,  
where A is an m by n real matrix, x is an m element real vector, y is an n-element real vector, and α is a real scalar.

4
References

None.

5
Arguments

1:     m – IntegerInput
On entry: m, the number of rows of the matrix A.
Constraint: m0.
2:     n – IntegerInput
On entry: n, the number of columns of the matrix A.
Constraint: n0.
3:     alpha – Real (Kind=nag_wp)Input
On entry: the scalar α.
4:     x* – Real (Kind=nag_wp) arrayInput
Note: the dimension of the array x must be at least max1, 1+m-1 ×incx .
On entry: the m element vector x.
If incx>0, xi must be stored in x1+i-1×incx, for i=1,2,,m.
If incx<0, xi must be stored in x1-m-i×incx, for i=1,2,,m.
Intermediate elements of x are not referenced.
5:     incx – IntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx0.
6:     y* – Real (Kind=nag_wp) arrayInput
Note: the dimension of the array y must be at least max1, 1+n-1 ×incy .
On entry: the n-element vector y.
If incy>0, yi must be stored in y1+i-1×incy, for i=1,2,,n.
If incy<0, yi must be stored in y1-n-i×incy, for i=1,2,,n.
Intermediate elements of y are not referenced.
7:     incy – IntegerInput
On entry: the increment in the subscripts of y between successive elements of y.
Constraint: incy0.
8:     alda* – Real (Kind=nag_wp) arrayInput/Output
Note: the second dimension of the array a must be at least n.
On entry: the m by n matrix A.
On exit: the updated matrix A.
9:     lda – IntegerInput
On entry: the first dimension of the array a as declared in the (sub)program from which f06pmf (dger) is called.
Constraint: lda max1,m .

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06pmf (dger) is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017