On Continuous Programming with Support Functions
Iqbal Husain1, Santosh K. Shrivastav1, Abdul Raoof Shah2 1
Department of Mathematics, Jaypee University of Engineering and Technology, Guna, India 2
Department of Statistics, University of Kashmir, Srinagar, India Email: [email protected]
Received June 12, 2013; revised July 12, 2013; accetped July 19, 2013
Copyright © 2013 Iqbal Husain etal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
A second-order Mond-Weir type dual problem is formulated for a class of continuous programming problems in which both objective and constraint functions contain support functions; hence it is nondifferentiable. Under second-order strict pseudoinvexity, second-order pseudoinvexity and second-order quasi-invexity assumptions on functionals, weak, strong, strict converse and converse duality theorems are established for this pair of dual continuous programming problems. Special cases are deduced and a pair of dual continuous problems with natural boundary values is constructed. A close relationship between the duality results of our problems and those of the corresponding (static) nonlinear pro-gramming problem with support functions is briefly outlined.
Keywords: Continuous Programming; Second-Order Generalized Invexity; Second-Order Duality; Nonlinear Programming; Support Functions; Natural Boundary Values
1. Introduction
Chen [1] was the first to identify second-order dual for-mulated for a constrained variational problem and estab-lished various duality results under an involved invexity- like assumptions. Husain etal. [2] have presented Mond- Weir type second-order duality for the problem of [1] and by introducing continuous-time version of second- order invexity and generalized second-order invexity, vali-dated various duality results. Subsequently, for a class of nondifferentiable continuous programming problems, Husain and Masoodi [3] studied Wolfe type second-order duality while Husain and Srivastava [4] investigated Mond- Weir type second-order duality. Recently, in the spirit of Mangasarian [5], Husain and Masoodi [6] studied Wolfe type second-order duality for a continuous programming problem having support functions appearing in the inte-grand of the functional as well as in the constraint func-tions under second-order invexity and second-order pseu-doinvexity conditions. They also incorporated a pair of second-order dual variational problems with natural bound-ary values rather than fixed end points and indicated their close relationship with those of corresponding (static) second-order duality results established for nonlinear pro-gramming problem with support functions, considered by Husain etal. [7]. The popularity of this type of nondif-ferentiable continuous programming problems seems to
originate from the fact that, even though the objective function and/or constraint functions are non-smooth, a simple representation of the dual problem may be written. The theory of non-smooth mathematical programming deals with more general type of functions by means of generalized subdifferentials. However, square root of posi-tive semi-definite quadratic form and support functions are amongst few cases of the nondifferentiable functions for which one can write down the subdifferentials explic-itly.
2. Pre-Requisites
Let I
a b, be a real interval :IRnRn Rand
:IRnRn Rm
be twice continuously
differenti-able functions. In order to consider
t x t,
,x t
, where x I: Rnis differentiable with derivative x
denoted by x and x the first order derivative of
with respect to x t
and x t
respectively, that is,T T
1, 2, , , 1, 2, ,
x n x n
x x x x x x
.
Denote by xx the n n Hessian matrix of and
x
the Jacobian matrix respectively, that is,
with respect to
mn
x t , that is,
2
, , 1, 2, ,
xx i j i j n
x x
x
the m n Jacobian
matrix.
1 1 1
1 2
2 2 2
1 2
1 2
n
n x
m m m
n m n
x x x
x x x
x x x
The symbols x, xx , xx andx
: n
have analogous rep-resentations. Designate by X the space of piecewise
smooth functions x IR , with the norm
x x Dx
dt
a
uDxx t
u s swhere the differentiation operator D
is given by , Thus d
dt D except at discontinuities.
We incorporate the following definitions which needed in the subsequent analysis:
Definition1. (Second-Order Invex):
If there exists a vector function
t x x, ,
Rnwhere : n n n
I R R R
and with 0
n n
at t = a
and t= b such that for a scalar function the
functional where
t x x, ,
, ,
dI
t x x t
:IR R R satisfies
T T
T T
1
, , d , , d
2
, , , , d .
I I
x x
I
t x x t t x x p t Gp t t
t x x D t x x Gp t t
Then
, ,
d is second-order invex with respectI
t x x t
to where Gxx2DxxD2xxD3xx,
, n
the space of -dimensional continuous
vector functions.
, nI R
pC
Definition 2. (Second-Order Pseudoinvex): If the func-
tional
, ,
dI
t x x t
satisfies
T
T T d 0
1
, , d , , d .
2
x x
I
T
I I
D Gp t p t t
t x x t t x x p t Gp t t
Then
, ,
dI
t x x t
is said to be second-order pseu-doinvex with respect to .
Definition 3. (Second-Order Strictly Pseudoinvex):
If the functional
, ,
dI
t x x t
satisfies
T
T T
T
d 0
1
, , d , , d ,
2
x x
I
I I
D Gp t t
t x x t t x x p t Gp t t
then
, ,
dI
t x x t
is said to be second-order strictlypseudoinvex with respect to .
Definition 4. (Second-Order Quasi-invex):
If the functional
, ,
dI
t x x t
satisfies
T T
T T
1
, , d , , d
2
d 0.
I I
x x
I
t x x t t x x p t Gp t t
D G t p t t
Then
, ,
dI
t x x t
is said to be second-order quasi-invex with respect to .
Consider the following nondifferentiable continuous programming problem with support functions treated by Husain and Jabeen [8]:
(CP): Minimize
, ,
dI
f t x x S x t K t
subject to
0
,x a x b (1)
, ,
0, 1, 2, , , ,j j
g t x x S x t C j m tI (2) where f and g are continuously differentiable and each
, 1, 2, ,
j
C j m is a compact convex set in Rn.
Husain and Jabeen [8] derived the following optimal-ity condition for (CP):
Lemma 1. (Fritz-John Necessary Optimality Con-ditions):
If the problem (CP) attains a minimum at x x X
then there exist rR and piecewise smooth functions
: m
y IR with
1
2
, , , m
: n
z IR and wj:IRn, j1, 2,, ,m such that
, ,
, , ,
j j
t g t x x
t x x t I
1 T
, ,
, ,
m
j
x x
j
x x
r f t x x z t y w t
D rf t x x y t g
T
1, , 0,
m
j j j
j
y t g t x x x t w t t I
T
,
x t z t S x t K tI
T
, 1, 2, , ,
j j
x t w t S x t C j m tI
, j
j, 1, 2, , ,z t K w t C j m tI
r y t,
0, tI
r y t,
0, tIThe minimum x t
of (CP) may be described asnormal if r 1, so that the Fritz John optimality tions reduce to Karush-Kuhn-Tucker optimality condi-tions. It suffices for r 1 that Slater’s [8] condition holds at x t
.Now we review some well known facts about a sup-port function for easy reference.
Let K be a compact set in , then the support
func-tion of is defined by
n
R K
T
max : , .
S x t K x t v t v t K tI
A support function, being convex everywhere finite, has a subdifferential in the sense of convex analysis i.e., there exist z t
R tn, I such that
T
.
S y t K S x t K y t x t z t
From [9], the subdifferential of S x t K
is given by
T
, such that .
S x t K z t K t I x t z t S x t K
For any set , the normal cone to at a point
is defined by
n
R
x t
n
0,
N x t y t R y t z t x t z t
It can be verified that for a compact convex set C,
if and only if
C
y t N x t
T, .
S y t C x t y t tI
3. Mond-Weir Type Second-Order Duality
In this section, we present the following problem as the Mond-Weir type dual to (CP) and validate usual duality theorems:
(M-WCD):
T 1
T
Maximize , , d
2
I
f t u u u t z t p t FP t t
subject to
0
u a u b
(3)
1
T
0
m
j j j
u u
j
u u
f z t y t g w t
D f y t g F G p t
(4)
T
T
11
d 2
m
j j j
j I
y t g u t t p t Gp t t
0
(5)
, j
j, , 1, 2,z t K w t C tI j ,m (6)
0,y t tI (7) where
1) p t
R tn, I2) F fuu2DfuuD f2 uu D f3 uu,tI
3) T
T
T
T
2 3
2
uu u
u
uu uu
G y t g D y t g
D y t g D y t g
Theorem 1. (Weak Duality): Let x t
X be fea-sible solution of (CP) and
u t ,y t ,z t ,w t1 ,w2 t ,,wm t ,p t
be feasible for (M-WCD). Assume that for all feasible
1 2
, , , , , , , m
x t u t y t z t w t w t w t
and with respect to vector function
t x u, ,
,1)
,.,. .T
dI
f t z t
t is second-order pseudo-invex and
2)
T T
1
,.,. . d
m
j j j
j I
y t g t w t t
is second-or-der quasi-invex. Then,
inf CP sup M-WCD
.Proof: Since x t
is feasible for (CP) and
1 2
, , , , , , m ,
u t y t z t w t w t w t p t
is feasible of (M-WCD), we have
1
T
1
T
, , d
, ,
1
d 2
m
j j j
j I m
j j j
j I
y t g t x x S x C t
y t g t u u u t w t
p t Gp t t
Using x t
Twj
t S x t
/Cj
,tI j, 1, 2,,m,we have,
T 1T 1
T
, , d
, ,
1
d . 2
m
j j j
j I
m
j j j
j I
y t g t x x x t w t t
y t g t u u u t w t
p t Gp t t
By the second-order quasi-invexity of
T
1,.,. . d ,
m
j j j
j I
y t g t w t t
for wj
t Rn, j1, 2,,m with respect to , from this we have,
T1
T T T
d 0
m
j j j
u j
I
u
y t g w t
D y t g Gp t t
.
By integrating by parts, we have
T
1
T T
T T
d
0.
m
j j j
u j
I
u
u
y t g w t
D y t g Gp t t
t b
t y t g
t a
Using 0, at ta and tb, this yields,
T 1
T
d 0
m
j j j
u j
I
u
y t g w t
D y t g Gp t t
Using equality constraint (4), we have
TT
T T
0
d
0, by integrating by parts
u u
I
u u
T u
f z t Df Fp t
f z t D f Fp t t
t b
f
t a
As earlier, this becomes
T T T
d 0
u u
I
f z t D f Fp t t
This, because of second-order pseudoinvexity of
T
,.,. . d , n,
I
f t z t t z t R t
I with respect to,
gives
TT T
, , d
1
, , d .
2
I
I
f t x x x t z t t
f t u u u t z t p t Fp t t
Since x t
Tz t S x t
K
,tI, we have
T
T
, , d
1
, , d ,
2
I
I
f t x x S x t K t
f t u u u t z t p t Fp t t
implying,
inf CP sup M-WCD
.Theorem 2. (Strong Duality):
If x t
X be an optimal solution of (CP) and isnormal, then there exist piecewise smooth functions
: m,
y IR : n and
z IR j: n
w IR such that
1 t ,p t 0
, , , , m
x t y t z t w t w is a
feasi-ble solution of (CD) and the two objective values are equal. Furthermore, if the hypothesis of Theorem1 holds,
then
1 , , m
,
, , ,
x t y t z t w t w t p t is an
op-timal solution of (M-WCD).
Proof: From Lemma 1 there exist piecewise smooth
functions y I: Rm, : n
z IR and j: n
w IR
j1, 2,,m
such that
1
, , , ,
, , , , 0,
m
j j j
x x
j
T
x x
f t x x z t y t g t x x w t
D f t x x y t g t x x t I
T
1, , 0,
m
j j j
j
y t g t x x x t w t t I
T
/ ,x t z t S x t K tI
T
/ , 1, 2, , ,
j j
x t w t S x t C j m tI
, j
j, 1, 2, , ,z t K w t C j m tI
0,y t tI
The above relations imply that
1
, , , , , m , 0
x t y t z t w t w t p t is feasible
for (M-WCD). Also
T
, , d
1
, , d .
2
I
I
f t x x S x t K t
f t x x x t z t p t Fp t t
This shows the equality of objective functions of the problem. Hence the optimality of
1
, , , , , m ,
follows from weak duality theorem (Theo
me that
(C is second-or
pseu is
second-order quasi-invex with respect to the same rem1).
Theorem 3 (Strict Converse Duality): Assu
1):
T
,.,. . d der strictlyI
f t z t t
doinvex and
1 m j I y t
T
,.,. .
j j j
g t w t
.
(C2): x t
is an optimal solution for (CP), If
, , ,z ,wm,p t is optimal solution of (M-
1 2, ,
u y w w
WCD), then
, I.Proof: We
u t x t t
assume that u t
x t
and show that a contradiction follows. Since x t
is aThe
n optimal solution
of (CP), it follows from orem 2, there exist
: m,
y IR z I: Rn and
,m
suc: ,
j n
w IR j1, 2, h that
x t ,y t ,z t ,w t1 ,w2 t ,,wm t ,p t 0
is optimal solution of (M-WCD). Since
1 2
,y t ,z t ,w t ,w t ,,wm t ,p t
is an optimal solution of (M-WCD), it follows that
u t
T
T, , d
1
, , d
2
I
I
f t x x x t z t t
f t u u u t z t p t Fp t t
This, because of the second-order strict pseudoinvexity
of for all
(8)
From the constraint of (CP) and (M-WCD), we have
T
Rngives
,.,. . d
I
f t z t t z t
T T T
d 0u u
I
f z t D f Fp t t
1 T 1 T, , d
, ,
1
d 2
m
j j j
j I
m
j j j
j I
y t g t x x S x t C t
y t g t u u u t w t
p t Gp t t
Using
T
, , 1, 2, ,
j j
,
x t w t S x t C tI j m
from this, we have
T 1 T 1 T, , d
, , 1 d 2 m j j j j I m
j j j
j I
y t g t x x x t w t t
y t g t u u u t w t
p t Gp t t
This, because of (C1) we have
T 1
T T T
, ,
d 0
m
j j j
u j
I
u
y t g t u u w t
D y g Gp t t
(9)Combining (8) and (9), we have
T 0 m jf z t y t g
1
T T T
T T T T d . j j u u j I u u m
j j j
u u
u u
w t
D f y t g F G p
f z t y t g w t
D f y t g F G p t t
t b
f y t g
t a
Using 1 u u j I
d t tat ta andtb, this implies
, 0,
T
d 0
m
T j j j
u u
j I
u u
f z t y t g w t
D f y t g F G p t t
contradicting the equality constraint of (M-WCD), hence
,u t x t tI
(Converse Duality):
(H1):
.
Theorem 4. Assume that
1 2
, , , , , , m ,
x t y t z t w t w t w t p t
mal solution of (M-WCD). is an opti
(H2): The vectors
F G ii, i, 1, 2,,m
i
are linear
independent where F and Gi
are the ith row of F and G respectively, and
(H3):
T
j j j
x x
y t g w t D y t g G t p t 0,
t I
and
(H4): either
T
d 0
xx I
p t T Gy t g p t t
d p t
T
1
d 0
m
j j j
x j
I
y t g w t t
an
T
T
d 0
xx I
p t Gy t g p t t
orand
j I p t
T 1 d 0 mj j j
x
y t g w t t
x t
Then is feasible for (CP) and the two objective
ionals have the same value. Also, if Theorem1 holds feasible solution of (CP) and (M-WCD), then funct
for all
Since
Proof:
1
, , , , , m ,
j
j j
C
t y t x t N w t
(14)x t y t z t w t w t p t
solution of (M-WCD), by results of Sc
s R, R
is an optimal hester [10], there
T
1
T
0 2
j j j
i I I
y t g x t w t p t Gp t
(15)
exist and piecewise sm
: n
ooth function
I R
and :IRm such that following Fritz
John optimality conditions are satisfied:
T
t y t 0,tI (16)
....
T T
3 4
T T
2 2
1 1
2 2
x x
x
xx xx x
t
D t D p t Fp t
t f Df y t g D y
T 2 T
T
T T
T 2
2 3
x
x
x
x x
xx x xx x
x x
xx x x
x
x x
D p t Fp t D p t Fp
p t Fp
t g
D f y t g D D f y t g
D Df y t g F G p t
D F G p t D F G p t
D F G
T1 2
x x
f z t Df p t Fp t
, t ,
0,tI (17)1 1
, t , t ,
0,tI (18) Using the hypothesis (H2) in (12), we have
t p t
0,t I (19)
t p t
0,t I (20)
Using (4), (19) and (20) in (10), we have (see (21) below)
Let 0, then (20) gives (19)
im-plies
t 0,t , I
p t
0,tI.
Consequently from (21), we have
1 T
, ,
0,
m
j j j
x j
x
y t g t x x w t
D y t g Gp t t I
....
....
4 T 1
T T
T T
2 3
T 4
1 1
2 2
1 1
2 2
1
0, 2
x x
m
j j j
x x
j
x x
x x
x
p t D F G p t
y t g w D y t g
p t Gp t D p t Gp t
D p t Gp t D p t Gp t
D p t Gp t
(10)
By the hypothesis (H3), this implies 0.
The relation (11) implies
t 0,tI.Hence
,
t , t ,
0 contradicting the Fritz John condition, Hence 0, & 0.
Pre-multiplying (11) by and Using (16), we
have
j
y t
TT 1 T
2 0,
j j j
x xx
j j j
xx
j
t g w t g p t
g x t w t p t g p t
t t I
T T
1
T
1
T T
1
0. 2
m
j j j
xx j
m
j j j
j
xx
t y t g w t y t g p t
y t g x t w t
p t y t g p t
(11)I
(12)
t p t
F
t p t
G0,t
k
x t t N z t
(13)
Integrating and then using (15), we have
....
T2
....
T T 2 T
1
T T
3 4 2
T T
3 4 2
T 3
2
m
T
j j j
x x
x x
j
T
x x x
x x
x x x x x
y t g w t D y t g G p t Fp t D p t Fp t D p t Fp t
D p t Fp t D p t Fp t t p t D F G p t D F G p t
D F G p t D F G p t t D p t Gp t D p t Gp t
D p t
....T 4
0,
x x
Gp t D p t Gp t tI
(21)
p t
F G
p t Gp
T T
1
T T T
d
d 0 2
m
j j j
x xx
j I
xx I
t y t g w t y t g p t
p t Gp t p t y t g p t t
t
Putting
t p
t we have
T1
T T
d
d 0 2
m
j j j
x j
I
xx I
p t y t g w t t
p t G y t g p t t
ives
d
of the hyp yields,
g
T
1
T T
2
d 0
m
j j j
x j
I
xx I
p t y t g w t t
p t G y t g p t t
This, in view othesis (H4)
0,p t tI we have x t
Nk
z t
and
j
, 1, 2, ,j
C .
x t N w t j m
These respectively imply x t
Tz t S
t K
and
x
T
, 1, 2, ,
j j
x t w t S x t C j m.
Multiplying the relation (11) by yj
tand using (16) ith
along w p t
0,tI, we have
T
10,
m
j j j
j
y t g x t w t t I
and also j
, ,
j
0,g t x x S x t C tI im lying the
feasibility of
p
x t for (CP).
Finally,
T
, d
1
d 2
I
f t x K t
T
, ,
,x S x t
I
f t x x t
x t z t p t Fp t
By Theorem 1, it implies that x t
i P).4. Special Cases
,
s an optimal so-lution of (C
Let for tI, A t
,Bj
t ,j1, 2,,mus on .
be positive
semidefinite matrices and continuo I
Then
1 2 T
, ,
x t A t x t S x t K tI where
T
1,
K A t z t z t A t z t tI
1 2
T
, 1, 2, , ,
j j .
x t B t x t S x t C j m tI
Replacing S x t
K
by
1 2 Tx t A t x t and
j
,S x t C
1 2T
, 1, 2, , ,
j
.
x t B t x t j m tI
We have the following problems:
d1 2 T
2
CP : Minimize , ,
I
f t x x x t A t x t
subject to
t
0
,x a x b
1 2 T, , 0,
, 1, 2, , .
j j
g t x x x t B t x t
t I j m
(M-WCD2):
T
T
Maximize , ,
1
d 2
f
I
t u u u t A t z
p t FP t t
subject to
t
0
,u a u b
m
j
j
1
T
, ,
, ,
, , , , 0,
u
j j
j
u u
f t u u A t z t
y t g t u u B t w t
D f t u u y t g t u u F G p t
u
by
t I
T
1
T
1
d 0 2
m
j j j j
j I
y t g u t B t t
p t Gp t t
T1,
z t A t z t tI
1, , 1, 2, ,j j j
w t B t w t tI j m
If
1 2 T j, 1, 2, ,
x t B t x t j m are suppressed
from the constraints of (CP2), we have the following
problem studied for duality by Husain and Srivastava [4].
1 2 T3
CP : Minimize , , d
I
f t x x x t A t x t t
subject to
0
x a x b
, ,
0, .g t x x tI
T
T
Maximize , ,
1
d 2
I
f t u u u t A t z t
p t FP t t
0
u a u b
T
T
, , , ,
, , , ,
0,
u u
u u
f t u u A t z t y t g t u u
D f t u u y t g t u u
F G p t t I
T
1
T
, , d 0,
2
I
y t g t u u p t Gp t t t I
T1,
z t A t z t tI
0, .y t tI
dual variational problems with natural boundary values rather than fixed end points.
5. Problems with Natural Boundary Values
In this section, we formulate a pair of nondifferentiable
CP : Minimize0
, ,
dI
f t x x S x t K t
subject to x a
0 x
b ,
, ,
0, , 1, 2 ,j j
g t x x S x t C tI j m
0T
T
- :
Maximize , ,
1
d 2
I
M WCD
f t u u u t z t
p t F t p t t
subject to
0
u a u b
T1 T
, , , ,
, , , ,
0,
m
j j j
u u
j
u u
f t u u z t y t g t u u w t
D f t u u y t g t u u
F G p t t I
T 1
T
, ,
1
d 0,
2
m
j j j
j I
y t g t u u u t w t
p t Gp t t t I
0,y t tI
, j
j, 1, 2, , ,z t K w t C j m tI
, ,
0 at and ,u
f t u u ta tb
T
, , at and .
u
g t u u 0, t a t b
y t
6. Nonlinear Programming Problems
If all functions in the problems (CP0) and (M-WCD0) are
independent of t, then these problems will reduce to the
following nonlinear programming problems ied by
Husain etal. [7]. (CP1):Minimize
stud
f x S x K
subject to
0, 1, 2, , .j j
g x S x C j m
T T1
1 CD : Maximize
2
f u u z p Fp
subject to
1
0
m
j j j
u u
j
f u z y g u w F G p
T
T1
1
0, 2
m
j j j
j
y g u w p Gp
, j j, 1, 2,
zK w C j , ,m
where F fuu
u andREFERENCES
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http://dx.doi.org/10.1016/S0022-247X(03)00481-5
.uu
Gy gT u
alit
[2] I. Husain, A. Ahmed and M. Masoodi, “Second Order Duality for Variational Problems,” European Journal of Pure and Applied Mathematics, Vol. 2, No. 2 009, pp. 278-295.
for a ming Pro-
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dx.doi.org/10.4236/ajor.2012.23035
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Class of Nondifferentiable Continuous Program
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2012, pp. 289-295.
http://
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dx.doi.org/10.1016/0022-247X(75)90111-0
er
http://
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http://dx.doi.org/10.4236/am.2010.16071
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ma matics, V , 2
ulletin of the Australian 1996, pp. 177-188.
So-
http://dx.doi.org/10.1017/S0004972700016890
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