approximation--♯P-complete
There are probabilistic algorithms that return good approximations to some #P-complete problems with high probability. This is one of the demonstrations of the power of probabilistic algorithms.
Many #P-complete problems have a fully polynomial-time randomized approximation scheme完全多項式時間乱択近似スキーム?!, or "FPRAS, " which, informally, will produce with high probability an approximation to an arbitrary degree of accuracy, in time that is polynomial with respect to both the size of the problem and the degree of accuracy required. Jerrum, Valiant, and Vazirani showed that every #P-complete problem either has an FPRAS, or is essentially impossible to approximate; if there is any polynomial-time algorithm which consistently produces an approximation of a #P-complete problem which is within a polynomial ratio in the size of the input of the exact answer, then that algorithm can be used to construct an FPRAS.
< https://en.wikipedia.org/wiki/Sharp-P-complete > ←< https://en.wikipedia.org/wiki/Hafnian >
↑↓
https://shinichiwanko2000.livedoor.blog/archives/29555317.html
2025年10月23日 computation, definition---Hafnianハフニアン
Many #P-complete problems have a fully polynomial-time randomized approximation scheme完全多項式時間乱択近似スキーム?!, or "FPRAS, " which, informally, will produce with high probability an approximation to an arbitrary degree of accuracy, in time that is polynomial with respect to both the size of the problem and the degree of accuracy required. Jerrum, Valiant, and Vazirani showed that every #P-complete problem either has an FPRAS, or is essentially impossible to approximate; if there is any polynomial-time algorithm which consistently produces an approximation of a #P-complete problem which is within a polynomial ratio in the size of the input of the exact answer, then that algorithm can be used to construct an FPRAS.
< https://en.wikipedia.org/wiki/Sharp-P-complete > ←< https://en.wikipedia.org/wiki/Hafnian >
↑↓
https://shinichiwanko2000.livedoor.blog/archives/29555317.html
2025年10月23日 computation, definition---Hafnianハフニアン
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