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*AIX Version 4.3 Base Operating System and Extensions Technical Reference, Volume 2*

## SAXPY, DAXPY, CAXPY, or ZAXPY Subroutine

### Purpose

Computes a constant times a vector plus a vector.

### Library

BLAS Library (**libblas.a**)

### FORTRAN Syntax

**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***(*)**

### Description

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

`Y`
`=`
`A *`
`X`
`+`
`Y`

### Parameters

*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. |

### Error Codes

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

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