Linear Program with finite optimal value has strictly complemenetary solution












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In my lecture, the following statement was given without any proof:



Given a primal-dual linear problem



(P) $${min~ c'x mid Ax=b, x geq 0}$$
(D) $${max~ b'y mid A'y+s=c, s geq 0},$$



it holds that:
If (P), (D) has a finite optimal value, then there exists a strictly complementary solution $(x^*,y^*,s^*)$, i.e., $x_i^* s_i^*=0 forall i$ and $x_i^* + s_i^* >0 forall i$.



Do I miss something here that this is actually obvious? I am grateful for any comments or hints!
Thank you!










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  • $begingroup$
    Intuitively, if $x_i=0$, the $i^{th}$ constraint in the dual is not binding (so $s_i>0$).
    $endgroup$
    – LinAlg
    Dec 5 '18 at 15:29


















0












$begingroup$


In my lecture, the following statement was given without any proof:



Given a primal-dual linear problem



(P) $${min~ c'x mid Ax=b, x geq 0}$$
(D) $${max~ b'y mid A'y+s=c, s geq 0},$$



it holds that:
If (P), (D) has a finite optimal value, then there exists a strictly complementary solution $(x^*,y^*,s^*)$, i.e., $x_i^* s_i^*=0 forall i$ and $x_i^* + s_i^* >0 forall i$.



Do I miss something here that this is actually obvious? I am grateful for any comments or hints!
Thank you!










share|cite|improve this question









$endgroup$












  • $begingroup$
    Intuitively, if $x_i=0$, the $i^{th}$ constraint in the dual is not binding (so $s_i>0$).
    $endgroup$
    – LinAlg
    Dec 5 '18 at 15:29
















0












0








0





$begingroup$


In my lecture, the following statement was given without any proof:



Given a primal-dual linear problem



(P) $${min~ c'x mid Ax=b, x geq 0}$$
(D) $${max~ b'y mid A'y+s=c, s geq 0},$$



it holds that:
If (P), (D) has a finite optimal value, then there exists a strictly complementary solution $(x^*,y^*,s^*)$, i.e., $x_i^* s_i^*=0 forall i$ and $x_i^* + s_i^* >0 forall i$.



Do I miss something here that this is actually obvious? I am grateful for any comments or hints!
Thank you!










share|cite|improve this question









$endgroup$




In my lecture, the following statement was given without any proof:



Given a primal-dual linear problem



(P) $${min~ c'x mid Ax=b, x geq 0}$$
(D) $${max~ b'y mid A'y+s=c, s geq 0},$$



it holds that:
If (P), (D) has a finite optimal value, then there exists a strictly complementary solution $(x^*,y^*,s^*)$, i.e., $x_i^* s_i^*=0 forall i$ and $x_i^* + s_i^* >0 forall i$.



Do I miss something here that this is actually obvious? I am grateful for any comments or hints!
Thank you!







linear-programming karush-kuhn-tucker






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asked Dec 5 '18 at 10:59









Andreas MuellerAndreas Mueller

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11












  • $begingroup$
    Intuitively, if $x_i=0$, the $i^{th}$ constraint in the dual is not binding (so $s_i>0$).
    $endgroup$
    – LinAlg
    Dec 5 '18 at 15:29




















  • $begingroup$
    Intuitively, if $x_i=0$, the $i^{th}$ constraint in the dual is not binding (so $s_i>0$).
    $endgroup$
    – LinAlg
    Dec 5 '18 at 15:29


















$begingroup$
Intuitively, if $x_i=0$, the $i^{th}$ constraint in the dual is not binding (so $s_i>0$).
$endgroup$
– LinAlg
Dec 5 '18 at 15:29






$begingroup$
Intuitively, if $x_i=0$, the $i^{th}$ constraint in the dual is not binding (so $s_i>0$).
$endgroup$
– LinAlg
Dec 5 '18 at 15:29












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