SAXPY, DAXPY, CAXPY, or ZAXPY Subroutine

Base Operating System and Extensions Technical Reference, Volume 2

Computes a constant times a vector plus a vector.

BLAS Library (libblas.a)

SUBROUTINE SAXPY(N,A,X,INCX,Y,INCY)
INTEGER INCX,INCY,N
REAL A
REAL X(*),Y(*)

SUBROUTINE DAXPY(N,A,X,INCX,Y,INCY)
INTEGER INCX,INCY,N
DOUBLE PRECISION A
DOUBLE PRECISION X(*),Y(*)

SUBROUTINE CAXPY(N,A,X,INCX,Y,INCY)
INTEGER INCX,INCY,N
COMPLEX A
COMPLEX X(*),Y(*)

SUBROUTINE ZAXPY(N,A,X,INCX,Y,INCY)
INTEGER INCX,INCY,N
COMPLEX*16 A
COMPLEX*16 X(*),Y(*)

The SAXPY, DAXPY, CAXPY, or ZAXPY subroutine computes a constant times a vector plus a vector:

Y = A * X + Y

N	On entry, N specifies the number of elements in X and Y; unchanged on exit.
A	On entry, A contains a constant to be multiplied by the X vector; unchanged on exit.
X	Vector of dimension at least (1 + (N-1) * abs(INCX) ); unchanged on exit.
INCX	On entry, INCX specifies the increment for the elements of X; unchanged on exit.
Y	Vector of dimension at least (1 + (N-1) * abs(INCY) ); the result is returned in vector Y.
INCY	On entry, INCY specifies the increment for the elements of Y; unchanged on exit.

If SA = 0 or N <= 0, the subroutine returns immediately.