Promote the Orthogonality between Rows of Matrix $ S $












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Suppose we want to solve the following optimization problem in $S in mathbb{R}^{N times T}$, where $T gg S$,



$$min_{S} f(S) mbox{ subject to } SS^T mbox{is diagonal}$$



which means rows of the matrix $S$ are mutually orthogonal.



I am suggested to solve this alternative problem by the following method:



$$min_{S} f(S) + |mathcal{P}(SS^T)|_1$$



in which $mathcal{P}$ is a projection onto the off-diagonal indexes.



But I don't this $ell_1$ penalty will promote the orthogonality between each rows by simply promote the sparsity of the off-diagonal elements, since we are not doing any actions like block coordinate descent to promote the orthogonality.



Any suggestions?










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  • $begingroup$
    What do you know about $f$? Why not introduce $n (n-1)$ quadratic equality constraints?
    $endgroup$
    – Rodrigo de Azevedo
    Jan 19 at 16:58












  • $begingroup$
    I think you should just rephrase the question into something like "Orthogonal Projection onto Semi Orthogonal Matrix Space". This way you'll get answers.
    $endgroup$
    – Royi
    Feb 3 at 4:09
















0












$begingroup$


Suppose we want to solve the following optimization problem in $S in mathbb{R}^{N times T}$, where $T gg S$,



$$min_{S} f(S) mbox{ subject to } SS^T mbox{is diagonal}$$



which means rows of the matrix $S$ are mutually orthogonal.



I am suggested to solve this alternative problem by the following method:



$$min_{S} f(S) + |mathcal{P}(SS^T)|_1$$



in which $mathcal{P}$ is a projection onto the off-diagonal indexes.



But I don't this $ell_1$ penalty will promote the orthogonality between each rows by simply promote the sparsity of the off-diagonal elements, since we are not doing any actions like block coordinate descent to promote the orthogonality.



Any suggestions?










share|cite|improve this question











$endgroup$












  • $begingroup$
    What do you know about $f$? Why not introduce $n (n-1)$ quadratic equality constraints?
    $endgroup$
    – Rodrigo de Azevedo
    Jan 19 at 16:58












  • $begingroup$
    I think you should just rephrase the question into something like "Orthogonal Projection onto Semi Orthogonal Matrix Space". This way you'll get answers.
    $endgroup$
    – Royi
    Feb 3 at 4:09














0












0








0





$begingroup$


Suppose we want to solve the following optimization problem in $S in mathbb{R}^{N times T}$, where $T gg S$,



$$min_{S} f(S) mbox{ subject to } SS^T mbox{is diagonal}$$



which means rows of the matrix $S$ are mutually orthogonal.



I am suggested to solve this alternative problem by the following method:



$$min_{S} f(S) + |mathcal{P}(SS^T)|_1$$



in which $mathcal{P}$ is a projection onto the off-diagonal indexes.



But I don't this $ell_1$ penalty will promote the orthogonality between each rows by simply promote the sparsity of the off-diagonal elements, since we are not doing any actions like block coordinate descent to promote the orthogonality.



Any suggestions?










share|cite|improve this question











$endgroup$




Suppose we want to solve the following optimization problem in $S in mathbb{R}^{N times T}$, where $T gg S$,



$$min_{S} f(S) mbox{ subject to } SS^T mbox{is diagonal}$$



which means rows of the matrix $S$ are mutually orthogonal.



I am suggested to solve this alternative problem by the following method:



$$min_{S} f(S) + |mathcal{P}(SS^T)|_1$$



in which $mathcal{P}$ is a projection onto the off-diagonal indexes.



But I don't this $ell_1$ penalty will promote the orthogonality between each rows by simply promote the sparsity of the off-diagonal elements, since we are not doing any actions like block coordinate descent to promote the orthogonality.



Any suggestions?







optimization convex-optimization






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Feb 3 at 4:07









Royi

3,52012352




3,52012352










asked Dec 21 '18 at 4:25









Z-HarlpetZ-Harlpet

327




327












  • $begingroup$
    What do you know about $f$? Why not introduce $n (n-1)$ quadratic equality constraints?
    $endgroup$
    – Rodrigo de Azevedo
    Jan 19 at 16:58












  • $begingroup$
    I think you should just rephrase the question into something like "Orthogonal Projection onto Semi Orthogonal Matrix Space". This way you'll get answers.
    $endgroup$
    – Royi
    Feb 3 at 4:09


















  • $begingroup$
    What do you know about $f$? Why not introduce $n (n-1)$ quadratic equality constraints?
    $endgroup$
    – Rodrigo de Azevedo
    Jan 19 at 16:58












  • $begingroup$
    I think you should just rephrase the question into something like "Orthogonal Projection onto Semi Orthogonal Matrix Space". This way you'll get answers.
    $endgroup$
    – Royi
    Feb 3 at 4:09
















$begingroup$
What do you know about $f$? Why not introduce $n (n-1)$ quadratic equality constraints?
$endgroup$
– Rodrigo de Azevedo
Jan 19 at 16:58






$begingroup$
What do you know about $f$? Why not introduce $n (n-1)$ quadratic equality constraints?
$endgroup$
– Rodrigo de Azevedo
Jan 19 at 16:58














$begingroup$
I think you should just rephrase the question into something like "Orthogonal Projection onto Semi Orthogonal Matrix Space". This way you'll get answers.
$endgroup$
– Royi
Feb 3 at 4:09




$begingroup$
I think you should just rephrase the question into something like "Orthogonal Projection onto Semi Orthogonal Matrix Space". This way you'll get answers.
$endgroup$
– Royi
Feb 3 at 4:09










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