*> \brief \b IZAMAX * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * * Definition: * =========== * * INTEGER FUNCTION IZAMAX(N,ZX,INCX) * * .. Scalar Arguments .. * INTEGER INCX,N * .. * .. Array Arguments .. * COMPLEX*16 ZX(*) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> IZAMAX finds the index of the first element having maximum |Re(.)| + |Im(.)| *> \endverbatim * * Arguments: * ========== * *> \param[in] N *> \verbatim *> N is INTEGER *> number of elements in input vector(s) *> \endverbatim *> *> \param[in] ZX *> \verbatim *> ZX is COMPLEX*16 array, dimension ( 1 + ( N - 1 )*abs( INCX ) ) *> \endverbatim *> *> \param[in] INCX *> \verbatim *> INCX is INTEGER *> storage spacing between elements of ZX *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \date November 2017 * *> \ingroup aux_blas * *> \par Further Details: * ===================== *> *> \verbatim *> *> jack dongarra, 1/15/85. *> modified 3/93 to return if incx .le. 0. *> modified 12/3/93, array(1) declarations changed to array(*) *> \endverbatim *> * ===================================================================== INTEGER FUNCTION IZAMAX(N,ZX,INCX) * * -- Reference BLAS level1 routine (version 3.8.0) -- * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * November 2017 * * .. Scalar Arguments .. INTEGER INCX,N * .. * .. Array Arguments .. COMPLEX*16 ZX(*) * .. * * ===================================================================== * * .. Local Scalars .. DOUBLE PRECISION DMAX INTEGER I,IX * .. * .. External Functions .. DOUBLE PRECISION DCABS1 EXTERNAL DCABS1 * .. IZAMAX = 0 IF (N.LT.1 .OR. INCX.LE.0) RETURN IZAMAX = 1 IF (N.EQ.1) RETURN IF (INCX.EQ.1) THEN * * code for increment equal to 1 * DMAX = DCABS1(ZX(1)) DO I = 2,N IF (DCABS1(ZX(I)).GT.DMAX) THEN IZAMAX = I DMAX = DCABS1(ZX(I)) END IF END DO ELSE * * code for increment not equal to 1 * IX = 1 DMAX = DCABS1(ZX(1)) IX = IX + INCX DO I = 2,N IF (DCABS1(ZX(IX)).GT.DMAX) THEN IZAMAX = I DMAX = DCABS1(ZX(IX)) END IF IX = IX + INCX END DO END IF RETURN END