dsxt1()

double precision function dsxt1	(	integer	ijob,
		double precision, dimension( * )	d1,
		integer	n1,
		double precision, dimension( * )	d2,
		integer	n2,
		double precision	abstol,
		double precision	ulp,
		double precision	unfl )

DSXT1

Purpose:

!>
!> 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 ) }
!> 

Parameters

[in]	IJOB	!> IJOB is INTEGER !> Specifies the type of tests to be performed. (See above.) !>
[in]	D1	!> D1 is DOUBLE PRECISION array, dimension (N1) !> The first array. D1 should be in increasing order, i.e., !> D1(j) <= D1(j+1). !>
[in]	N1	!> N1 is INTEGER !> The length of D1. !>
[in]	D2	!> D2 is DOUBLE PRECISION array, dimension (N2) !> The second array. D2 should be in increasing order, i.e., !> D2(j) <= D2(j+1). !>
[in]	N2	!> N2 is INTEGER !> The length of D2. !>
[in]	ABSTOL	!> ABSTOL is DOUBLE PRECISION !> The absolute tolerance, used as a measure of the error. !>
[in]	ULP	!> ULP is DOUBLE PRECISION !> Machine precision. !>
[in]	UNFL	!> UNFL is DOUBLE PRECISION !> The smallest positive number whose reciprocal does not !> overflow. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 104 of file dsxt1.f.

*
*  -- LAPACK test routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. 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
*

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