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Let CVal be the language of all $<C,s>$ where $s$ is an $n-$tuple of binary values ($\{0,1\}$), such that $C$ is a variable-free boolean circuit (gates $\wedge$, $\vee$, $\neg$, $0$, $1$), and it outputs $1$ for the entries of $s=(x_1,...,x_n)$.

Given two languages $A,B$, define $A \leq ^{rand} B$ iff there exists a random turing machine $M_f$ with $O(\log n)$ memory, such that for each $x$:

  • if $x\notin A$ so $f(x)\notin B$
  • else, if $x\in A$, then $P(f(x) \in B) \geq \frac{1}{2}$.

I'd like to show that for each $A\in RP$ exists such a random reduction: $A\leq^{rand} CVal$.

My thoughts were to prove this similarly to how it can be proven that for any $A\in P$ exists a log-space reduction $A\leq_l CVal$ . Meaning, I'd like to show that for every $n$ I can construct $C_n$ such that in probability $\geq \frac{1}{2}$ $\,:\,\,$ $C_n(x)=1$ for every $x$ in length $n$ which is in $A$, and for each $x$ not in $A$ $C_n(x)=0$ for sure, but I'm not sure if perhaps there is an easier way for showing a random reduction $A\leq_{rand} CVal$ for each $A\in RP$?

Thanks!

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  • $\begingroup$ The circuit value problem is actually P-complete, see e.g. cs.cornell.edu/Courses/cs6820/2012sp/Handouts/cvp.pdf. $\endgroup$ Commented Jan 27, 2015 at 18:23
  • $\begingroup$ I'm having trouble understanding what you mean by "it outputs $1$ under the values given by $s$ to it's variables $x_1,\dots,x_n$". Can you rephrase/elaborate? $\endgroup$
    – D.W.
    Commented Jan 27, 2015 at 21:28
  • $\begingroup$ @YuvalFilmus I know, but I'm trying to prove here that it is also $RP$-hard (or perhaps complete), through similar way, but not sure it can be done so. $\endgroup$ Commented Jan 28, 2015 at 8:03
  • $\begingroup$ @D.W. I mean that you have single bit inputs $x_1,...,x_n$, and $s$ is telling me for each $i$ whether $x_i =1$ or $x_i=0$, and in $CVAL$ Im checking whether the output of the entire circuit is $1$ or $0$. $\endgroup$ Commented Jan 28, 2015 at 8:05
  • $\begingroup$ Try extending the proof that $\mathsf{CVAL}$ is P-complete under deterministic reductions to a proof that $\mathsf{CVAL}$ is RP-complete under randomized reductions. $\endgroup$ Commented Jan 28, 2015 at 16:22

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