107 lines
2.3 KiB
Fortran
107 lines
2.3 KiB
Fortran
*> \brief \b IDAMAX
|
|
*
|
|
* =========== DOCUMENTATION ===========
|
|
*
|
|
* Online html documentation available at
|
|
* http://www.netlib.org/lapack/explore-html/
|
|
*
|
|
* Definition:
|
|
* ===========
|
|
*
|
|
* INTEGER FUNCTION IDAMAX(N,DX,INCX)
|
|
*
|
|
* .. Scalar Arguments ..
|
|
* INTEGER INCX,N
|
|
* ..
|
|
* .. Array Arguments ..
|
|
* DOUBLE PRECISION DX(*)
|
|
* ..
|
|
*
|
|
*
|
|
*> \par Purpose:
|
|
* =============
|
|
*>
|
|
*> \verbatim
|
|
*>
|
|
*> IDAMAX finds the index of element having max. absolute value.
|
|
*> \endverbatim
|
|
*
|
|
* Authors:
|
|
* ========
|
|
*
|
|
*> \author Univ. of Tennessee
|
|
*> \author Univ. of California Berkeley
|
|
*> \author Univ. of Colorado Denver
|
|
*> \author NAG Ltd.
|
|
*
|
|
*> \date November 2011
|
|
*
|
|
*> \ingroup aux_blas
|
|
*
|
|
*> \par Further Details:
|
|
* =====================
|
|
*>
|
|
*> \verbatim
|
|
*>
|
|
*> jack dongarra, linpack, 3/11/78.
|
|
*> modified 3/93 to return if incx .le. 0.
|
|
*> modified 12/3/93, array(1) declarations changed to array(*)
|
|
*> \endverbatim
|
|
*>
|
|
* =====================================================================
|
|
INTEGER FUNCTION IDAMAX(N,DX,INCX)
|
|
*
|
|
* -- Reference BLAS level1 routine (version 3.4.0) --
|
|
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
|
|
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
|
|
* November 2011
|
|
*
|
|
* .. Scalar Arguments ..
|
|
INTEGER INCX,N
|
|
* ..
|
|
* .. Array Arguments ..
|
|
DOUBLE PRECISION DX(*)
|
|
* ..
|
|
*
|
|
* =====================================================================
|
|
*
|
|
* .. Local Scalars ..
|
|
DOUBLE PRECISION DMAX
|
|
INTEGER I,IX
|
|
* ..
|
|
* .. Intrinsic Functions ..
|
|
INTRINSIC DABS
|
|
* ..
|
|
IDAMAX = 0
|
|
IF (N.LT.1 .OR. INCX.LE.0) RETURN
|
|
IDAMAX = 1
|
|
IF (N.EQ.1) RETURN
|
|
IF (INCX.EQ.1) THEN
|
|
*
|
|
* code for increment equal to 1
|
|
*
|
|
DMAX = DABS(DX(1))
|
|
DO I = 2,N
|
|
IF (DABS(DX(I)).GT.DMAX) THEN
|
|
IDAMAX = I
|
|
DMAX = DABS(DX(I))
|
|
END IF
|
|
END DO
|
|
ELSE
|
|
*
|
|
* code for increment not equal to 1
|
|
*
|
|
IX = 1
|
|
DMAX = DABS(DX(1))
|
|
IX = IX + INCX
|
|
DO I = 2,N
|
|
IF (DABS(DX(IX)).GT.DMAX) THEN
|
|
IDAMAX = I
|
|
DMAX = DABS(DX(IX))
|
|
END IF
|
|
IX = IX + INCX
|
|
END DO
|
|
END IF
|
|
RETURN
|
|
END
|