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*DECK SAXPY
SUBROUTINE SAXPY(N,SA,SX,INCX,SY,INCY)
*
*-----------------------------------------------------------------------
*
*Purpose:
* constant times a vector plus a vector. Uses unrolled loop for
* increments equal to one.
*
*Copyright:
* Copyright (C) 2002 Ecole Polytechnique de Montreal
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version
*
*Author(s): Jack Dongarra, linpack, 3/11/78.
*
*Parameters: input
* N number of components in the vector.
* SA constant.
* SX RHS vector.
* INCX increment in RHS vector.
*
*Parameters: output
* SY LHS vector.
* INCY increment in LHS vector.
*
*-----------------------------------------------------------------------
*
*----
* SUBROUTINE ARGUMENTS
*----
REAL SX(N*INCX),SY(N*INCY),SA
INTEGER N,INCX,INCY
*----
* LOCAL VARIABLES
*----
INTEGER I,IX,IY,M,MP1
*
IF(N.LE.0)RETURN
IF (SA .EQ. 0.0) RETURN
IF(INCX.EQ.1.AND.INCY.EQ.1)GO TO 20
*----
* CODE FOR UNEQUAL INCREMENTS OR EQUAL INCREMENTS NOT EQUAL TO 1.
*----
IX = 1
IY = 1
IF(INCX.LT.0)IX = (-N+1)*INCX + 1
IF(INCY.LT.0)IY = (-N+1)*INCY + 1
DO 10 I = 1,N
SY(IY) = SY(IY) + SA*SX(IX)
IX = IX + INCX
IY = IY + INCY
10 CONTINUE
RETURN
*----
* CODE FOR BOTH INCREMENTS EQUAL TO 1. CLEAN-UP LOOP.
*----
20 M = MOD(N,4)
IF( M .EQ. 0 ) GO TO 40
DO 30 I = 1,M
SY(I) = SY(I) + SA*SX(I)
30 CONTINUE
IF( N .LT. 4 ) RETURN
40 MP1 = M + 1
DO 50 I = MP1,N,4
SY(I) = SY(I) + SA*SX(I)
SY(I + 1) = SY(I + 1) + SA*SX(I + 1)
SY(I + 2) = SY(I + 2) + SA*SX(I + 2)
SY(I + 3) = SY(I + 3) + SA*SX(I + 3)
50 CONTINUE
RETURN
END
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