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*DECK SDOT
REAL FUNCTION SDOT(N,SX,INCX,SY,INCY)
*
*-----------------------------------------------------------------------
*
*Purpose:
* forms the dot product of two vectors. Uses unrolled loops 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 vectors.
* SX first vector.
* INCX increment in first vector.
* SY second vector.
* INCY increment in second vector.
*
*Parameters: output
* SDOT dot product.
*
*-----------------------------------------------------------------------
*
*----
* SUBROUTINE ARGUMENTS
*----
INTEGER N,INCX,INCY
REAL SX(N*INCX),SY(N*INCY)
*----
* LOCAL VARIABLES
*----
INTEGER I,IX,IY,M,MP1
REAL STEMP
*
STEMP = 0.0E0
SDOT = 0.0E0
IF(N.LE.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
STEMP = STEMP + SX(IX)*SY(IY)
IX = IX + INCX
IY = IY + INCY
10 CONTINUE
SDOT = STEMP
RETURN
*----
* CODE FOR BOTH INCREMENTS EQUAL TO 1. CLEAN-UP LOOP.
*----
20 M = MOD(N,5)
IF( M .EQ. 0 ) GO TO 40
DO 30 I = 1,M
STEMP = STEMP + SX(I)*SY(I)
30 CONTINUE
IF( N .LT. 5 ) GO TO 60
40 MP1 = M + 1
DO 50 I = MP1,N,5
STEMP = STEMP + SX(I)*SY(I) + SX(I + 1)*SY(I + 1) +
* SX(I + 2)*SY(I + 2) + SX(I + 3)*SY(I + 3) + SX(I + 4)*SY(I + 4)
50 CONTINUE
60 SDOT = STEMP
RETURN
END
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