ssxt1()

real function ssxt1	(	integer	IJOB,
		real, dimension( * )	D1,
		integer	N1,
		real, dimension( * )	D2,
		integer	N2,
		real	ABSTOL,
		real	ULP,
		real	UNFL
	)

SSXT1

Purpose:

 SSXT1  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 REAL 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 REAL 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 REAL The absolute tolerance, used as a measure of the error.
[in]	ULP	ULP is REAL Machine precision.
[in]	UNFL	UNFL is REAL The smallest positive number whose reciprocal does not overflow.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date

December 2016

Definition at line 108 of file ssxt1.f.

*
*  -- LAPACK test routine (version 3.7.0) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     December 2016
*
*     .. Scalar Arguments ..
      INTEGER            IJOB, N1, N2
      REAL               ABSTOL, ULP, UNFL
*     ..
*     .. Array Arguments ..
      REAL               D1( * ), D2( * )
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ZERO
      parameter( zero = 0.0e0 )
*     ..
*     .. Local Scalars ..
      INTEGER            I, J
      REAL               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
*
      ssxt1 = temp1
      RETURN
*
*     End of SSXT1
*