149 lines
3.1 KiB
FortranFixed
149 lines
3.1 KiB
FortranFixed
*> \brief \b SAXPBY
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE SAXPBY(N,SA,SX,INCX,SB,SY,INCY)
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*
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* .. Scalar Arguments ..
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* REAL SA,SB
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* INTEGER INCX,INCY,N
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* ..
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* .. Array Arguments ..
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* REAL SX(*),SY(*)
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> SAXPBY constant times a vector plus constant times a vector.
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*>
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*> Y = ALPHA * X + BETA * Y
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*>
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> number of elements in input vector(s)
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*> \endverbatim
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*>
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*> \param[in] SA
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*> \verbatim
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*> SA is REAL
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*> On entry, SA specifies the scalar alpha.
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*> \endverbatim
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*>
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*> \param[in] SX
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*> \verbatim
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*> SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
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*> \endverbatim
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*>
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*> \param[in] INCX
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*> \verbatim
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*> INCX is INTEGER
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*> storage spacing between elements of SX
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*> \endverbatim
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*>
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*> \param[in] SB
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*> \verbatim
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*> SB is REAL
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*> On entry, SB specifies the scalar beta.
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*> \endverbatim
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*>
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*> \param[in,out] SY
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*> \verbatim
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*> SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
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*> \endverbatim
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*>
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*> \param[in] INCY
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*> \verbatim
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*> INCY is INTEGER
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*> storage spacing between elements of SY
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*> \author Martin Koehler, MPI Magdeburg
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*
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*> \ingroup axpby
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*
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* =====================================================================
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SUBROUTINE SAXPBY(N,SA,SX,INCX,SB,SY,INCY)
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IMPLICIT NONE
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*
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* -- Reference BLAS level1 routine --
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* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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*
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* .. Scalar Arguments ..
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REAL SA,SB
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INTEGER INCX,INCY,N
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* ..
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* .. Array Arguments ..
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REAL SX(*),SY(*)
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* ..
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* .. External Subroutines ..
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EXTERNAL SSCAL
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I,IX,IY,M,MP1
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC MOD
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* ..
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IF (N.LE.0) RETURN
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* Scale if SA.EQ.0
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IF (SA.EQ.0.0E0 .AND. SB.NE.0.0E0) THEN
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CALL SSCAL(N, SB, SY, INCY)
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RETURN
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END IF
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IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
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*
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* code for both increments equal to 1
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*
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DO I = 1,N
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SY(I) = SB*SY(I) + SA*SX(I)
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END DO
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ELSE
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*
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* code for unequal increments or equal increments
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* not equal to 1
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*
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IX = 1
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IY = 1
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IF (INCX.LT.0) IX = (-N+1)*INCX + 1
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IF (INCY.LT.0) IY = (-N+1)*INCY + 1
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DO I = 1,N
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SY(IY) = SB*SY(IY) + SA*SX(IX)
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IX = IX + INCX
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IY = IY + INCY
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END DO
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END IF
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RETURN
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*
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* End of SAXPBY
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*
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END
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