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# Technical Reference: Base Operating System and Extensions , Volume 2

## SGER or DGER Subroutine

### Purpose

Performs the rank 1 operation.

### Library

BLAS Library (libblas.a)

### FORTRAN Syntax

SUBROUTINE SGER(M, N, ALPHA, X,
INCX, Y, INCY, A, LDA)
REAL ALPHA
INTEGER INCX, INCY, LDA, M, N
REAL A(LDA,*), X(*), Y(*)

```SUBROUTINE DGER(M, N, ALPHA, X,
INCX, Y, INCY, A, LDA)
DOUBLE PRECISION ALPHA
INTEGER INCX,INCY,LDA,M,N
DOUBLE PRECISION A(LDA,*), X(*), Y(*)
```

### Description

The SGER or DGER subroutine performs the rank 1 operation:

A := alpha * x * y' + 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.

### Parameters

 M On entry, M specifies the number of rows of the matrix A; M must be at least 0; unchanged on exit. N On entry, N specifies the number of columns of the matrix A; N must be at least 0; unchanged on exit. ALPHA On entry, ALPHA specifies the scalar alpha; unchanged on exit. X A vector of dimension at least (1 + (M-1) * abs(INCX) ); on entry, the incremented array X must contain the M element vector x; unchanged on exit. INCX On entry, INCX specifies the increment for the elements of X; INCX must not be 0; unchanged on exit. Y A vector of dimension at least (1 + (N-1) * abs(INCY) ); on entry, the incremented array Y must contain the N element vector y; unchanged on exit. INCY On entry, INCY specifies the increment for the elements of Y; INCY must not be 0; unchanged on exit. A An array of dimension ( LDA, N ); on entry, the leading M by N part of the array A must contain the matrix of coefficients; on exit, A is overwritten by the updated matrix. LDA On entry, LDA specifies the first dimension of A as declared in the calling (sub) program; LDA must be at least max( 1, M ); unchanged on exit.

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