Is there a non-deterministic version of the complexity class PP?

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From a quick skim of the literature (and complexity zoo), there doesn't seem to be a non-deterministic version of PP. Is there a reason for this (e.g. PP=non-deterministic PP?)










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  • How would such a complexity class be defined?
    – Sasho Nikolov
    8 hours ago














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From a quick skim of the literature (and complexity zoo), there doesn't seem to be a non-deterministic version of PP. Is there a reason for this (e.g. PP=non-deterministic PP?)










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  • How would such a complexity class be defined?
    – Sasho Nikolov
    8 hours ago












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down vote

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1









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From a quick skim of the literature (and complexity zoo), there doesn't seem to be a non-deterministic version of PP. Is there a reason for this (e.g. PP=non-deterministic PP?)










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From a quick skim of the literature (and complexity zoo), there doesn't seem to be a non-deterministic version of PP. Is there a reason for this (e.g. PP=non-deterministic PP?)







cc.complexity-theory complexity-classes time-complexity






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asked 10 hours ago









user138901

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  • How would such a complexity class be defined?
    – Sasho Nikolov
    8 hours ago
















  • How would such a complexity class be defined?
    – Sasho Nikolov
    8 hours ago















How would such a complexity class be defined?
– Sasho Nikolov
8 hours ago




How would such a complexity class be defined?
– Sasho Nikolov
8 hours ago










2 Answers
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PP is defined as a probabilistic class and we don't normally think of nondeterministic versions of any of these classes (as far as I'm aware). In a sense probabilistic classes and nondeterministic ones are already on the same spectrum -- let me illustrate. We can define a language to be in PP if there's a randomized poly-time TM ("RPTM") that on a yes instance accepts with $> 0.5$ probability and on a no instance accepts with $leq 0.5$ probability. Similarly we can define a language to be in NP if there's a RPTM accepting yes-instances w.prob $> 0$ and accepting no-instances w.prob $0$. (Convince yourself of this if you haven't before.) BPP corresponds to probability thresholds $geq 2/3$ and $leq 1/3$ while RP corresponds to $geq 1/2$ and $0$.



So you see, PP can already be viewed as a "nondeterministic" version of P, but with different requirements as compared to NP.






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    It does not really make sense to define an “X-version of class Y”, this is a misguided viewpoint. You define classes because they are useful or interesting in whatever context you are investigating, not to fill a slot in an imaginary table. So, what would count as a nondeterministic version of PP depends very much on what you intend to do with the class.



    Having said that, in view of $mathrmP^=PP$, one reasonable option is to define a nondeterministic version of PP as $mathrmNP^$. Actually, this should equal $existsmathrmPP$.






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      PP is defined as a probabilistic class and we don't normally think of nondeterministic versions of any of these classes (as far as I'm aware). In a sense probabilistic classes and nondeterministic ones are already on the same spectrum -- let me illustrate. We can define a language to be in PP if there's a randomized poly-time TM ("RPTM") that on a yes instance accepts with $> 0.5$ probability and on a no instance accepts with $leq 0.5$ probability. Similarly we can define a language to be in NP if there's a RPTM accepting yes-instances w.prob $> 0$ and accepting no-instances w.prob $0$. (Convince yourself of this if you haven't before.) BPP corresponds to probability thresholds $geq 2/3$ and $leq 1/3$ while RP corresponds to $geq 1/2$ and $0$.



      So you see, PP can already be viewed as a "nondeterministic" version of P, but with different requirements as compared to NP.






      share|cite|improve this answer
























        up vote
        4
        down vote













        PP is defined as a probabilistic class and we don't normally think of nondeterministic versions of any of these classes (as far as I'm aware). In a sense probabilistic classes and nondeterministic ones are already on the same spectrum -- let me illustrate. We can define a language to be in PP if there's a randomized poly-time TM ("RPTM") that on a yes instance accepts with $> 0.5$ probability and on a no instance accepts with $leq 0.5$ probability. Similarly we can define a language to be in NP if there's a RPTM accepting yes-instances w.prob $> 0$ and accepting no-instances w.prob $0$. (Convince yourself of this if you haven't before.) BPP corresponds to probability thresholds $geq 2/3$ and $leq 1/3$ while RP corresponds to $geq 1/2$ and $0$.



        So you see, PP can already be viewed as a "nondeterministic" version of P, but with different requirements as compared to NP.






        share|cite|improve this answer






















          up vote
          4
          down vote










          up vote
          4
          down vote









          PP is defined as a probabilistic class and we don't normally think of nondeterministic versions of any of these classes (as far as I'm aware). In a sense probabilistic classes and nondeterministic ones are already on the same spectrum -- let me illustrate. We can define a language to be in PP if there's a randomized poly-time TM ("RPTM") that on a yes instance accepts with $> 0.5$ probability and on a no instance accepts with $leq 0.5$ probability. Similarly we can define a language to be in NP if there's a RPTM accepting yes-instances w.prob $> 0$ and accepting no-instances w.prob $0$. (Convince yourself of this if you haven't before.) BPP corresponds to probability thresholds $geq 2/3$ and $leq 1/3$ while RP corresponds to $geq 1/2$ and $0$.



          So you see, PP can already be viewed as a "nondeterministic" version of P, but with different requirements as compared to NP.






          share|cite|improve this answer












          PP is defined as a probabilistic class and we don't normally think of nondeterministic versions of any of these classes (as far as I'm aware). In a sense probabilistic classes and nondeterministic ones are already on the same spectrum -- let me illustrate. We can define a language to be in PP if there's a randomized poly-time TM ("RPTM") that on a yes instance accepts with $> 0.5$ probability and on a no instance accepts with $leq 0.5$ probability. Similarly we can define a language to be in NP if there's a RPTM accepting yes-instances w.prob $> 0$ and accepting no-instances w.prob $0$. (Convince yourself of this if you haven't before.) BPP corresponds to probability thresholds $geq 2/3$ and $leq 1/3$ while RP corresponds to $geq 1/2$ and $0$.



          So you see, PP can already be viewed as a "nondeterministic" version of P, but with different requirements as compared to NP.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 4 hours ago









          usul

          5,01911435




          5,01911435




















              up vote
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              It does not really make sense to define an “X-version of class Y”, this is a misguided viewpoint. You define classes because they are useful or interesting in whatever context you are investigating, not to fill a slot in an imaginary table. So, what would count as a nondeterministic version of PP depends very much on what you intend to do with the class.



              Having said that, in view of $mathrmP^=PP$, one reasonable option is to define a nondeterministic version of PP as $mathrmNP^$. Actually, this should equal $existsmathrmPP$.






              share|cite|improve this answer
























                up vote
                2
                down vote













                It does not really make sense to define an “X-version of class Y”, this is a misguided viewpoint. You define classes because they are useful or interesting in whatever context you are investigating, not to fill a slot in an imaginary table. So, what would count as a nondeterministic version of PP depends very much on what you intend to do with the class.



                Having said that, in view of $mathrmP^=PP$, one reasonable option is to define a nondeterministic version of PP as $mathrmNP^$. Actually, this should equal $existsmathrmPP$.






                share|cite|improve this answer






















                  up vote
                  2
                  down vote










                  up vote
                  2
                  down vote









                  It does not really make sense to define an “X-version of class Y”, this is a misguided viewpoint. You define classes because they are useful or interesting in whatever context you are investigating, not to fill a slot in an imaginary table. So, what would count as a nondeterministic version of PP depends very much on what you intend to do with the class.



                  Having said that, in view of $mathrmP^=PP$, one reasonable option is to define a nondeterministic version of PP as $mathrmNP^$. Actually, this should equal $existsmathrmPP$.






                  share|cite|improve this answer












                  It does not really make sense to define an “X-version of class Y”, this is a misguided viewpoint. You define classes because they are useful or interesting in whatever context you are investigating, not to fill a slot in an imaginary table. So, what would count as a nondeterministic version of PP depends very much on what you intend to do with the class.



                  Having said that, in view of $mathrmP^=PP$, one reasonable option is to define a nondeterministic version of PP as $mathrmNP^$. Actually, this should equal $existsmathrmPP$.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered 2 hours ago









                  Emil Jeřábek

                  10.3k33459




                  10.3k33459



























                       

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