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LAPACK
3.4.1
LAPACK: Linear Algebra PACKage
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00001 *> \brief \b IZAMAX 00002 * 00003 * =========== DOCUMENTATION =========== 00004 * 00005 * Online html documentation available at 00006 * http://www.netlib.org/lapack/explore-html/ 00007 * 00008 * Definition: 00009 * =========== 00010 * 00011 * INTEGER FUNCTION IZAMAX(N,ZX,INCX) 00012 * 00013 * .. Scalar Arguments .. 00014 * INTEGER INCX,N 00015 * .. 00016 * .. Array Arguments .. 00017 * COMPLEX*16 ZX(*) 00018 * .. 00019 * 00020 * 00021 *> \par Purpose: 00022 * ============= 00023 *> 00024 *> \verbatim 00025 *> 00026 *> IZAMAX finds the index of element having max. absolute value. 00027 *> \endverbatim 00028 * 00029 * Authors: 00030 * ======== 00031 * 00032 *> \author Univ. of Tennessee 00033 *> \author Univ. of California Berkeley 00034 *> \author Univ. of Colorado Denver 00035 *> \author NAG Ltd. 00036 * 00037 *> \date November 2011 00038 * 00039 *> \ingroup aux_blas 00040 * 00041 *> \par Further Details: 00042 * ===================== 00043 *> 00044 *> \verbatim 00045 *> 00046 *> jack dongarra, 1/15/85. 00047 *> modified 3/93 to return if incx .le. 0. 00048 *> modified 12/3/93, array(1) declarations changed to array(*) 00049 *> \endverbatim 00050 *> 00051 * ===================================================================== 00052 INTEGER FUNCTION IZAMAX(N,ZX,INCX) 00053 * 00054 * -- Reference BLAS level1 routine (version 3.4.0) -- 00055 * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- 00056 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 00057 * November 2011 00058 * 00059 * .. Scalar Arguments .. 00060 INTEGER INCX,N 00061 * .. 00062 * .. Array Arguments .. 00063 COMPLEX*16 ZX(*) 00064 * .. 00065 * 00066 * ===================================================================== 00067 * 00068 * .. Local Scalars .. 00069 DOUBLE PRECISION DMAX 00070 INTEGER I,IX 00071 * .. 00072 * .. External Functions .. 00073 DOUBLE PRECISION DCABS1 00074 EXTERNAL DCABS1 00075 * .. 00076 IZAMAX = 0 00077 IF (N.LT.1 .OR. INCX.LE.0) RETURN 00078 IZAMAX = 1 00079 IF (N.EQ.1) RETURN 00080 IF (INCX.EQ.1) THEN 00081 * 00082 * code for increment equal to 1 00083 * 00084 DMAX = DCABS1(ZX(1)) 00085 DO I = 2,N 00086 IF (DCABS1(ZX(I)).GT.DMAX) THEN 00087 IZAMAX = I 00088 DMAX = DCABS1(ZX(I)) 00089 END IF 00090 END DO 00091 ELSE 00092 * 00093 * code for increment not equal to 1 00094 * 00095 IX = 1 00096 DMAX = DCABS1(ZX(1)) 00097 IX = IX + INCX 00098 DO I = 2,N 00099 IF (DCABS1(ZX(IX)).GT.DMAX) THEN 00100 IZAMAX = I 00101 DMAX = DCABS1(ZX(IX)) 00102 END IF 00103 IX = IX + INCX 00104 END DO 00105 END IF 00106 RETURN 00107 END