112 lines
2.5 KiB
Fortran
112 lines
2.5 KiB
Fortran
*> \brief \b DASUM
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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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* DOUBLE PRECISION FUNCTION DASUM(N,DX,INCX)
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*
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* .. Scalar Arguments ..
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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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*> DASUM takes the sum of the absolute values.
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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 2011
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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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DOUBLE PRECISION FUNCTION DASUM(N,DX,INCX)
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*
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* -- Reference BLAS level1 routine (version 3.4.0) --
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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 2011
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*
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* .. Scalar Arguments ..
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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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DOUBLE PRECISION DTEMP
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INTEGER I,M,MP1,NINCX
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC DABS,MOD
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* ..
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DASUM = 0.0d0
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DTEMP = 0.0d0
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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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* 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,6)
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IF (M.NE.0) THEN
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DO I = 1,M
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DTEMP = DTEMP + DABS(DX(I))
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END DO
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IF (N.LT.6) THEN
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DASUM = DTEMP
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RETURN
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END IF
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END IF
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MP1 = M + 1
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DO I = MP1,N,6
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DTEMP = DTEMP + DABS(DX(I)) + DABS(DX(I+1)) +
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$ DABS(DX(I+2)) + DABS(DX(I+3)) +
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$ DABS(DX(I+4)) + DABS(DX(I+5))
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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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DTEMP = DTEMP + DABS(DX(I))
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END DO
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END IF
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DASUM = DTEMP
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RETURN
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END
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