What is the main characteristics of separable and non-separable functions?












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I have read an article that says, from the optimization point of view, the separable functions are simpler then non-separable functions and optimization algorithms can find their optimal values more easily. What are the main characteristics of separable functions which cause such behavior?










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    $begingroup$


    I have read an article that says, from the optimization point of view, the separable functions are simpler then non-separable functions and optimization algorithms can find their optimal values more easily. What are the main characteristics of separable functions which cause such behavior?










    share|cite|improve this question









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      $begingroup$


      I have read an article that says, from the optimization point of view, the separable functions are simpler then non-separable functions and optimization algorithms can find their optimal values more easily. What are the main characteristics of separable functions which cause such behavior?










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      I have read an article that says, from the optimization point of view, the separable functions are simpler then non-separable functions and optimization algorithms can find their optimal values more easily. What are the main characteristics of separable functions which cause such behavior?







      optimization






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      asked May 18 '18 at 6:55









      Payam AbdyPayam Abdy

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          $begingroup$

          I have a partial knowledge on that subject but this may give you (very ?) few understandings.



          Let us say that you want to minimize the function $f : mathbb{R}^{2} rightarrow mathbb{R}$ which can be written:



          $$forall (x,y) in mathbb{R}^{2} ; f(x,y) = g(x) + h(y)$$ because it is separable.



          Then, $min_{(x,y)}f(x,y) = min_{x}g(x) + min_{y}h(y)$, which transforms your initial problem on $mathbb{R}^{2}$ into two problems on $mathbb{R}$. This can be easier to solve.



          You could also transform a complex problem of minimization along one variable into two simpler problems of minimization along two variables by simply adding an equality constraint:



          $$min_{x}g(x) + h(Ax) = min_{(x,y); s.t ;y = Ax}g(x) + h(y)$$






          share|cite|improve this answer









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            $begingroup$

            I have a partial knowledge on that subject but this may give you (very ?) few understandings.



            Let us say that you want to minimize the function $f : mathbb{R}^{2} rightarrow mathbb{R}$ which can be written:



            $$forall (x,y) in mathbb{R}^{2} ; f(x,y) = g(x) + h(y)$$ because it is separable.



            Then, $min_{(x,y)}f(x,y) = min_{x}g(x) + min_{y}h(y)$, which transforms your initial problem on $mathbb{R}^{2}$ into two problems on $mathbb{R}$. This can be easier to solve.



            You could also transform a complex problem of minimization along one variable into two simpler problems of minimization along two variables by simply adding an equality constraint:



            $$min_{x}g(x) + h(Ax) = min_{(x,y); s.t ;y = Ax}g(x) + h(y)$$






            share|cite|improve this answer









            $endgroup$


















              1












              $begingroup$

              I have a partial knowledge on that subject but this may give you (very ?) few understandings.



              Let us say that you want to minimize the function $f : mathbb{R}^{2} rightarrow mathbb{R}$ which can be written:



              $$forall (x,y) in mathbb{R}^{2} ; f(x,y) = g(x) + h(y)$$ because it is separable.



              Then, $min_{(x,y)}f(x,y) = min_{x}g(x) + min_{y}h(y)$, which transforms your initial problem on $mathbb{R}^{2}$ into two problems on $mathbb{R}$. This can be easier to solve.



              You could also transform a complex problem of minimization along one variable into two simpler problems of minimization along two variables by simply adding an equality constraint:



              $$min_{x}g(x) + h(Ax) = min_{(x,y); s.t ;y = Ax}g(x) + h(y)$$






              share|cite|improve this answer









              $endgroup$
















                1












                1








                1





                $begingroup$

                I have a partial knowledge on that subject but this may give you (very ?) few understandings.



                Let us say that you want to minimize the function $f : mathbb{R}^{2} rightarrow mathbb{R}$ which can be written:



                $$forall (x,y) in mathbb{R}^{2} ; f(x,y) = g(x) + h(y)$$ because it is separable.



                Then, $min_{(x,y)}f(x,y) = min_{x}g(x) + min_{y}h(y)$, which transforms your initial problem on $mathbb{R}^{2}$ into two problems on $mathbb{R}$. This can be easier to solve.



                You could also transform a complex problem of minimization along one variable into two simpler problems of minimization along two variables by simply adding an equality constraint:



                $$min_{x}g(x) + h(Ax) = min_{(x,y); s.t ;y = Ax}g(x) + h(y)$$






                share|cite|improve this answer









                $endgroup$



                I have a partial knowledge on that subject but this may give you (very ?) few understandings.



                Let us say that you want to minimize the function $f : mathbb{R}^{2} rightarrow mathbb{R}$ which can be written:



                $$forall (x,y) in mathbb{R}^{2} ; f(x,y) = g(x) + h(y)$$ because it is separable.



                Then, $min_{(x,y)}f(x,y) = min_{x}g(x) + min_{y}h(y)$, which transforms your initial problem on $mathbb{R}^{2}$ into two problems on $mathbb{R}$. This can be easier to solve.



                You could also transform a complex problem of minimization along one variable into two simpler problems of minimization along two variables by simply adding an equality constraint:



                $$min_{x}g(x) + h(Ax) = min_{(x,y); s.t ;y = Ax}g(x) + h(y)$$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 25 at 8:50









                AlbertoAlberto

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