# HPL_dger man page

HPL_dger — A := alpha * x * y^T + A.

## Synopsis

**#include "hpl.h"****void HPL_dger( const enum HPL_ORDER** *ORDER*, **const int** *M*, **const int** *N*, **const double** *ALPHA*, **const double *** *X*, **const int** *INCX*, **double *** *Y*, **const int** *INCY*, **double *** *A*, **const int** *LDA* **);**

## Description

**HPL_dger** performs the rank 1 operation

A := alpha * x * y^T + A,

where alpha is a scalar, x is an m-element vector, y is an n-element vector and A is an m by n matrix.

## Arguments

- ORDER (local input) const enum HPL_ORDER
- On entry, ORDER specifies the storage format of the operands as follows:

ORDER = HplRowMajor,

ORDER = HplColumnMajor. - M (local input) const int
- On entry, M specifies the number of rows of the matrix A. M must be at least zero.
- N (local input) const int
- On entry, N specifies the number of columns of the matrix A. N must be at least zero.
- ALPHA (local input) const double
- On entry, ALPHA specifies the scalar alpha. When ALPHA is supplied as zero then X and Y need not be set on input.
- X (local input) const double *
- On entry, X is an incremented array of dimension at least ( 1 + ( m - 1 ) * abs( INCX ) ) that contains the vector x.
- INCX (local input) const int
- On entry, INCX specifies the increment for the elements of X. INCX must not be zero.
- Y (local input) double *
- On entry, Y is an incremented array of dimension at least ( 1 + ( n - 1 ) * abs( INCY ) ) that contains the vector y.
- INCY (local input) const int
- On entry, INCY specifies the increment for the elements of Y. INCY must not be zero.
- A (local input/output) double *
- On entry, A points to an array of size equal to or greater than LDA * n. Before entry, the leading m by n part of the array A must contain the matrix coefficients. On exit, A is overwritten by the updated matrix.
- LDA (local input) const int
- On entry, LDA specifies the leading dimension of A as declared in the calling (sub) program. LDA must be at least MAX(1,m).

## Example

*#include "hpl.h"*

int main(int argc, char *argv[])

{

double a[2*2], x[2], y[2];

a[0] = 1.0; a[1] = 2.0; a[2] = 3.0; a[3] = 3.0;

x[0] = 2.0; x[1] = 1.0; y[2] = 1.0; y[3] = 2.0;

HPL_dger( HplColumnMajor, 2, 2, 2.0, x, 1, y, 1,

a, 2 );

printf("y=[%f,%f]\n", y[0], y[1]);

exit(0); return(0);

}

## See Also

**HPL_dgemv** (3), **HPL_dtrsv** (3).