diff --git a/semester3/ti-compact/parts/04_computability.tex b/semester3/ti-compact/parts/04_computability.tex index 9d8e458..1512d14 100644 --- a/semester3/ti-compact/parts/04_computability.tex +++ b/semester3/ti-compact/parts/04_computability.tex @@ -152,3 +152,6 @@ For the third condition, intuitively, we only need to check if in the definition or the condition can be restated such that only $L(M)$ is described by it. For a more formal proof of that condition, simply show that the implication holds + + +As of HS2025, chapters 5.5 and 5.6 are not relevant for the Endterm or Session exam, so they are omitted here diff --git a/semester3/ti-compact/parts/05_complexity.tex b/semester3/ti-compact/parts/05_complexity.tex index 8df6e7a..1ff627b 100644 --- a/semester3/ti-compact/parts/05_complexity.tex +++ b/semester3/ti-compact/parts/05_complexity.tex @@ -1,3 +1,54 @@ \newsection \section{Complexity} \label{sec:complexity} +\stepcounter{subsection} +\subsection{Measurements of Complexity} +\compactdef{Time complexity} For a computation $D = C_1, \ldots, C_k$ of $M$ on $x$ is defined by $\text{Time}_M(x) = k - 1$. +For the TM $M$ itself, we have $\text{Time}_M(n) = \max\{ \text{Time}_M(x) \divides x \in \Sigma^n \}$ + +\begin{definition}[]{Space complexity} + Let $C = (q, x, i, \alpha_1, i_1, \ldots, \alpha_k, i_k)$, + with $0 \leq i \leq |x| + 1$ and $0 \leq i_j \leq |\alpha_j|$ for $j = 1, \ldots, k$ be a configuration. + + The space complexity of configuration $C$ is $\text{Space}_M(C) = \max\{ |\alpha_i| \divides i = 1, \ldots, k \}$. + + The space complexity of a calculation $D = C_1, \ldots, C_l$ on $x$ is $\text{Space}_M(x) = \max\{ \text{Space}_M(C_i) \divides i = 1, \ldots, l \}$ + + The space complexity of a TM $M$ is $\text{Space}_M(n) = \max\{ \text{Space}_M(x) \divides x \in \Sigma^n \}$ +\end{definition} + +\inlinelemma For every $k$-tape-TM $A$, there exists an equivalent $1$-tape-TM $B$ such that $\text{Space}_B(n) \leq \text{Space}_A(n)$ + +\inlinelemma For every $k$-tape-TM $A$, $\exists$ a $k$-tape-TM such that $L(A) = L(B)$ and $\text{Space}_B(n) \leq \frac{\text{Space}_A(n)}{2} + 2$ + +\inlinedef The big-O-notation is defined as in A\&D, we however write $\text{Time}_A(n) \in \tco{g(n)}$, etc + +\inlinedef An MTM $C$ is \bi{optimal} for $L$, if $\text{Time}_C(n) \in \tco{f(n)}$ and $\tcl(f(n))$ is a lower bound for the time complexity of $L$ + + +\subsection{Complexity classes} +Below is a list of complexity classes +\begin{definition}[]{Complexity classes} + \begin{align*} + \text{TIME}(f) & = \{ L(B) \divides B \text{ is an MTM with } \tc_B(n) \in \tco{f(n)} \} \\ + \text{SPACE}(g) & = \{ L(A) \divides A \text{ is an MTM with } \spc_A(n) \in \tco{g(n)} \} \\ + \text{DLOG} & = \text{SPACE}(\log_2(n)) \\ + \text{P} & = \bigcup_{c \in \N} \text{TIME}(n^c) \\ + \text{PSPACE} & = \bigcup_{c \in \N} \text{SPACE}(n^c) \\ + \text{EXPTIME} & = \bigcup_{d \in \N} \text{TIME}(2^{n^d}) + \end{align*} +\end{definition} + +For any function $t : \N \rightarrow \R^+$, we have $\text{TIME}(t(n)) \subseteq \text{SPACE}(t(n))$. +A list of relationships for these classes: +\rmvspace +\begin{multicols}{2} + \begin{itemize} + \item $P \subseteq \text{PSPACE}$ + \item $\text{DLOG} \subseteq P$ + \item $\text{PSPACE} \subseteq \text{EXPTIME}$ + \item $\text{DLOG} \subseteq P \subseteq \text{PSPACE} \subseteq \text{EXPTIME} + \end{itemize} +\end{multicols} + +\inlinedef diff --git a/semester3/ti-compact/ti-compact.pdf b/semester3/ti-compact/ti-compact.pdf index 2b8e146..5e83028 100644 Binary files a/semester3/ti-compact/ti-compact.pdf and b/semester3/ti-compact/ti-compact.pdf differ