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*> \brief \b DSXT1
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition
* ==========
*
* DOUBLE PRECISION FUNCTION DSXT1( IJOB, D1, N1, D2, N2, ABSTOL,
* ULP, UNFL )
*
* .. Scalar Arguments ..
* INTEGER IJOB, N1, N2
* DOUBLE PRECISION ABSTOL, ULP, UNFL
* ..
* .. Array Arguments ..
* DOUBLE PRECISION D1( * ), D2( * )
* ..
*
* Purpose
* =======
*
*>\details \b Purpose:
*>\verbatim
*>
*> DSXT1 computes the difference between a set of eigenvalues.
*> The result is returned as the function value.
*>
*> IJOB = 1: Computes max { min | D1(i)-D2(j) | }
*> i j
*>
*> IJOB = 2: Computes max { min | D1(i)-D2(j) | /
*> i j
*> ( ABSTOL + |D1(i)|*ULP ) }
*>
*>\endverbatim
*
* Arguments
* =========
*
*> \param[in] ITYPE
*> \verbatim
*> ITYPE is INTEGER
*> Specifies the type of tests to be performed. (See above.)
*> \endverbatim
*>
*> \param[in] D1
*> \verbatim
*> D1 is DOUBLE PRECISION array, dimension (N1)
*> The first array. D1 should be in increasing order, i.e.,
*> D1(j) <= D1(j+1).
*> \endverbatim
*>
*> \param[in] N1
*> \verbatim
*> N1 is INTEGER
*> The length of D1.
*> \endverbatim
*>
*> \param[in] D2
*> \verbatim
*> D2 is DOUBLE PRECISION array, dimension (N2)
*> The second array. D2 should be in increasing order, i.e.,
*> D2(j) <= D2(j+1).
*> \endverbatim
*>
*> \param[in] N2
*> \verbatim
*> N2 is INTEGER
*> The length of D2.
*> \endverbatim
*>
*> \param[in] ABSTOL
*> \verbatim
*> ABSTOL is DOUBLE PRECISION
*> The absolute tolerance, used as a measure of the error.
*> \endverbatim
*>
*> \param[in] ULP
*> \verbatim
*> ULP is DOUBLE PRECISION
*> Machine precision.
*> \endverbatim
*>
*> \param[in] UNFL
*> \verbatim
*> UNFL is DOUBLE PRECISION
*> The smallest positive number whose reciprocal does not
*> overflow.
*> \endverbatim
*>
*
* Authors
* =======
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup double_eig
*
* =====================================================================
DOUBLE PRECISION FUNCTION DSXT1( IJOB, D1, N1, D2, N2, ABSTOL,
$ ULP, UNFL )
*
* -- LAPACK test routine (version 3.1) --
* -- LAPACK 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 IJOB, N1, N2
DOUBLE PRECISION ABSTOL, ULP, UNFL
* ..
* .. Array Arguments ..
DOUBLE PRECISION D1( * ), D2( * )
* ..
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ZERO
PARAMETER ( ZERO = 0.0D0 )
* ..
* .. Local Scalars ..
INTEGER I, J
DOUBLE PRECISION TEMP1, TEMP2
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, MAX, MIN
* ..
* .. Executable Statements ..
*
TEMP1 = ZERO
*
J = 1
DO 20 I = 1, N1
10 CONTINUE
IF( D2( J ).LT.D1( I ) .AND. J.LT.N2 ) THEN
J = J + 1
GO TO 10
END IF
IF( J.EQ.1 ) THEN
TEMP2 = ABS( D2( J )-D1( I ) )
IF( IJOB.EQ.2 )
$ TEMP2 = TEMP2 / MAX( UNFL, ABSTOL+ULP*ABS( D1( I ) ) )
ELSE
TEMP2 = MIN( ABS( D2( J )-D1( I ) ),
$ ABS( D1( I )-D2( J-1 ) ) )
IF( IJOB.EQ.2 )
$ TEMP2 = TEMP2 / MAX( UNFL, ABSTOL+ULP*ABS( D1( I ) ) )
END IF
TEMP1 = MAX( TEMP1, TEMP2 )
20 CONTINUE
*
DSXT1 = TEMP1
RETURN
*
* End of DSXT1
*
END
|
