LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ 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.

Definition at line 104 of file ssxt1.f.

106 *
107 * -- LAPACK test routine --
108 * -- LAPACK is a software package provided by Univ. of Tennessee, --
109 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
110 *
111 * .. Scalar Arguments ..
112  INTEGER IJOB, N1, N2
113  REAL ABSTOL, ULP, UNFL
114 * ..
115 * .. Array Arguments ..
116  REAL D1( * ), D2( * )
117 * ..
118 *
119 * =====================================================================
120 *
121 * .. Parameters ..
122  REAL ZERO
123  parameter( zero = 0.0e0 )
124 * ..
125 * .. Local Scalars ..
126  INTEGER I, J
127  REAL TEMP1, TEMP2
128 * ..
129 * .. Intrinsic Functions ..
130  INTRINSIC abs, max, min
131 * ..
132 * .. Executable Statements ..
133 *
134  temp1 = zero
135 *
136  j = 1
137  DO 20 i = 1, n1
138  10 CONTINUE
139  IF( d2( j ).LT.d1( i ) .AND. j.LT.n2 ) THEN
140  j = j + 1
141  GO TO 10
142  END IF
143  IF( j.EQ.1 ) THEN
144  temp2 = abs( d2( j )-d1( i ) )
145  IF( ijob.EQ.2 )
146  $ temp2 = temp2 / max( unfl, abstol+ulp*abs( d1( i ) ) )
147  ELSE
148  temp2 = min( abs( d2( j )-d1( i ) ),
149  $ abs( d1( i )-d2( j-1 ) ) )
150  IF( ijob.EQ.2 )
151  $ temp2 = temp2 / max( unfl, abstol+ulp*abs( d1( i ) ) )
152  END IF
153  temp1 = max( temp1, temp2 )
154  20 CONTINUE
155 *
156  ssxt1 = temp1
157  RETURN
158 *
159 * End of SSXT1
160 *
real function ssxt1(IJOB, D1, N1, D2, N2, ABSTOL, ULP, UNFL)
SSXT1
Definition: ssxt1.f:106