96 lines
2.1 KiB
FortranFixed
96 lines
2.1 KiB
FortranFixed
INTEGER FUNCTION IZMAX1( N, CX, INCX )
|
|
*
|
|
* -- LAPACK auxiliary routine (version 3.1) --
|
|
* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
|
|
* November 2006
|
|
*
|
|
* .. Scalar Arguments ..
|
|
INTEGER INCX, N
|
|
* ..
|
|
* .. Array Arguments ..
|
|
COMPLEX*16 CX( * )
|
|
* ..
|
|
*
|
|
* Purpose
|
|
* =======
|
|
*
|
|
* IZMAX1 finds the index of the element whose real part has maximum
|
|
* absolute value.
|
|
*
|
|
* Based on IZAMAX from Level 1 BLAS.
|
|
* The change is to use the 'genuine' absolute value.
|
|
*
|
|
* Contributed by Nick Higham for use with ZLACON.
|
|
*
|
|
* Arguments
|
|
* =========
|
|
*
|
|
* N (input) INTEGER
|
|
* The number of elements in the vector CX.
|
|
*
|
|
* CX (input) COMPLEX*16 array, dimension (N)
|
|
* The vector whose elements will be summed.
|
|
*
|
|
* INCX (input) INTEGER
|
|
* The spacing between successive values of CX. INCX >= 1.
|
|
*
|
|
* =====================================================================
|
|
*
|
|
* .. Local Scalars ..
|
|
INTEGER I, IX
|
|
DOUBLE PRECISION SMAX
|
|
COMPLEX*16 ZDUM
|
|
* ..
|
|
* .. Intrinsic Functions ..
|
|
INTRINSIC ABS
|
|
* ..
|
|
* .. Statement Functions ..
|
|
DOUBLE PRECISION CABS1
|
|
* ..
|
|
* .. Statement Function definitions ..
|
|
*
|
|
* NEXT LINE IS THE ONLY MODIFICATION.
|
|
CABS1( ZDUM ) = ABS( ZDUM )
|
|
* ..
|
|
* .. Executable Statements ..
|
|
*
|
|
IZMAX1 = 0
|
|
IF( N.LT.1 )
|
|
$ RETURN
|
|
IZMAX1 = 1
|
|
IF( N.EQ.1 )
|
|
$ RETURN
|
|
IF( INCX.EQ.1 )
|
|
$ GO TO 30
|
|
*
|
|
* CODE FOR INCREMENT NOT EQUAL TO 1
|
|
*
|
|
IX = 1
|
|
SMAX = CABS1( CX( 1 ) )
|
|
IX = IX + INCX
|
|
DO 20 I = 2, N
|
|
IF( CABS1( CX( IX ) ).LE.SMAX )
|
|
$ GO TO 10
|
|
IZMAX1 = I
|
|
SMAX = CABS1( CX( IX ) )
|
|
10 CONTINUE
|
|
IX = IX + INCX
|
|
20 CONTINUE
|
|
RETURN
|
|
*
|
|
* CODE FOR INCREMENT EQUAL TO 1
|
|
*
|
|
30 CONTINUE
|
|
SMAX = CABS1( CX( 1 ) )
|
|
DO 40 I = 2, N
|
|
IF( CABS1( CX( I ) ).LE.SMAX )
|
|
$ GO TO 40
|
|
IZMAX1 = I
|
|
SMAX = CABS1( CX( I ) )
|
|
40 CONTINUE
|
|
RETURN
|
|
*
|
|
* End of IZMAX1
|
|
*
|
|
END
|