DEGTRIDL.SIF

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* SET UP THE INITIAL DATA *
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NAME          DEGTRIDL

*   Problem :
*   *********

*   A degenerate bound constrained convex quadratic program
*   with a tri-diagonal Hessian

*   SIF input: Nick Gould, August 2011

*   classification QLR2-AN-V-1

*   The number of variables - 1

*IE N                   10
*IE N                   50
*IE N                   100
*IE N                   1000
*IE N                   10000
 IE N                   100000

*  Other useful values.

 IE 0                   0
 IE 1                   1
 IE 2                   2
 IA N-1       N         -1
 IA N+1       N         1

 RI RN        N
 RI RN+1      N+1


VARIABLES

 DO I         0                        N
 X  X(I)
 ND

GROUPS

 XN OBJ       X(0)      0.5
 XN OBJ       X(1)      -0.5
 DO I         2                        N-1
 XN OBJ       X(I)      -1.0
 ND
 XN OBJ       X(N)      -0.5

 DO I         0                        N
 XE CON       X(I)      1.0
 ND

RHS

 Z  DEGTRIDL  CON                      RN

BOUNDS

*LO DEGTRID2  'DEFAULT' 0.0
*UP DEGTRID2  'DEFAULT' 2.0

START POINT

 XV DEGTRID   'DEFAULT' 2.0

QUADRATIC

 X  X(0)      X(0)      1.0
 DO I         1                        N
 IA I-1       I         -1
 X  X(I)      X(I)      1.0
 X  X(I)      X(I-1)    0.5
 ND

OBJECT BOUND

*   Solution

ENDATA