Annotation of rpl/lapack/blas/idamax.f, revision 1.8
1.8 ! bertrand 1: *> \brief \b IDAMAX
! 2: *
! 3: * =========== DOCUMENTATION ===========
! 4: *
! 5: * Online html documentation available at
! 6: * http://www.netlib.org/lapack/explore-html/
! 7: *
! 8: * Definition:
! 9: * ===========
! 10: *
! 11: * INTEGER FUNCTION IDAMAX(N,DX,INCX)
! 12: *
! 13: * .. Scalar Arguments ..
! 14: * INTEGER INCX,N
! 15: * ..
! 16: * .. Array Arguments ..
! 17: * DOUBLE PRECISION DX(*)
! 18: * ..
! 19: *
! 20: *
! 21: *> \par Purpose:
! 22: * =============
! 23: *>
! 24: *> \verbatim
! 25: *>
! 26: *> IDAMAX finds the index of element having max. absolute value.
! 27: *> \endverbatim
! 28: *
! 29: * Authors:
! 30: * ========
! 31: *
! 32: *> \author Univ. of Tennessee
! 33: *> \author Univ. of California Berkeley
! 34: *> \author Univ. of Colorado Denver
! 35: *> \author NAG Ltd.
! 36: *
! 37: *> \date November 2011
! 38: *
! 39: *> \ingroup aux_blas
! 40: *
! 41: *> \par Further Details:
! 42: * =====================
! 43: *>
! 44: *> \verbatim
! 45: *>
! 46: *> jack dongarra, linpack, 3/11/78.
! 47: *> modified 3/93 to return if incx .le. 0.
! 48: *> modified 12/3/93, array(1) declarations changed to array(*)
! 49: *> \endverbatim
! 50: *>
! 51: * =====================================================================
1.1 bertrand 52: INTEGER FUNCTION IDAMAX(N,DX,INCX)
1.8 ! bertrand 53: *
! 54: * -- Reference BLAS level1 routine (version 3.4.0) --
! 55: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
! 56: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 57: * November 2011
! 58: *
1.1 bertrand 59: * .. Scalar Arguments ..
60: INTEGER INCX,N
61: * ..
62: * .. Array Arguments ..
63: DOUBLE PRECISION DX(*)
64: * ..
65: *
66: * =====================================================================
67: *
68: * .. Local Scalars ..
69: DOUBLE PRECISION DMAX
70: INTEGER I,IX
71: * ..
72: * .. Intrinsic Functions ..
73: INTRINSIC DABS
74: * ..
75: IDAMAX = 0
76: IF (N.LT.1 .OR. INCX.LE.0) RETURN
77: IDAMAX = 1
78: IF (N.EQ.1) RETURN
1.7 bertrand 79: IF (INCX.EQ.1) THEN
1.1 bertrand 80: *
1.7 bertrand 81: * code for increment equal to 1
1.1 bertrand 82: *
1.7 bertrand 83: DMAX = DABS(DX(1))
84: DO I = 2,N
85: IF (DABS(DX(I)).GT.DMAX) THEN
86: IDAMAX = I
87: DMAX = DABS(DX(I))
88: END IF
89: END DO
90: ELSE
1.1 bertrand 91: *
1.7 bertrand 92: * code for increment not equal to 1
1.1 bertrand 93: *
1.7 bertrand 94: IX = 1
95: DMAX = DABS(DX(1))
96: IX = IX + INCX
97: DO I = 2,N
98: IF (DABS(DX(IX)).GT.DMAX) THEN
99: IDAMAX = I
100: DMAX = DABS(DX(IX))
101: END IF
102: IX = IX + INCX
103: END DO
104: END IF
1.1 bertrand 105: RETURN
106: END
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