137 lines
2.9 KiB
Fortran
137 lines
2.9 KiB
Fortran
*> \brief \b DSCAL
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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 DSCAL(N,DA,DX,INCX)
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*
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* .. Scalar Arguments ..
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* DOUBLE PRECISION DA
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* INTEGER INCX,N
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* ..
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* .. Array Arguments ..
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* DOUBLE PRECISION DX(*)
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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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*> DSCAL scales a vector by a constant.
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*> uses unrolled loops for increment equal to 1.
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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] DA
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*> \verbatim
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*> DA is DOUBLE PRECISION
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*> On entry, DA specifies the scalar alpha.
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*> \endverbatim
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*>
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*> \param[in,out] DX
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*> \verbatim
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*> DX is DOUBLE PRECISION 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 DX
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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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*
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*> \date November 2017
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*
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*> \ingroup double_blas_level1
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*
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*> \par Further Details:
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* =====================
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*>
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*> \verbatim
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*>
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*> jack dongarra, linpack, 3/11/78.
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*> modified 3/93 to return if incx .le. 0.
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*> modified 12/3/93, array(1) declarations changed to array(*)
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*> \endverbatim
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*>
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* =====================================================================
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SUBROUTINE DSCAL(N,DA,DX,INCX)
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*
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* -- Reference BLAS level1 routine (version 3.8.0) --
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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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* November 2017
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*
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* .. Scalar Arguments ..
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DOUBLE PRECISION DA
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INTEGER INCX,N
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* ..
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* .. Array Arguments ..
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DOUBLE PRECISION DX(*)
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I,M,MP1,NINCX
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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 .OR. INCX.LE.0) RETURN
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IF (INCX.EQ.1) THEN
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*
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* code for increment equal to 1
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*
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*
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* clean-up loop
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*
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M = MOD(N,5)
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IF (M.NE.0) THEN
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DO I = 1,M
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DX(I) = DA*DX(I)
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END DO
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IF (N.LT.5) RETURN
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END IF
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MP1 = M + 1
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DO I = MP1,N,5
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DX(I) = DA*DX(I)
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DX(I+1) = DA*DX(I+1)
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DX(I+2) = DA*DX(I+2)
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DX(I+3) = DA*DX(I+3)
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DX(I+4) = DA*DX(I+4)
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END DO
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ELSE
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*
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* code for increment not equal to 1
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*
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NINCX = N*INCX
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DO I = 1,NINCX,INCX
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DX(I) = DA*DX(I)
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END DO
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END IF
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RETURN
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END
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