afl-material: comparison slides/slides09.tex

equal deleted inserted replaced

-:55c9f30d0ed2
+:e03107e79d26
 \documentclass[dvipsnames,14pt,t]{beamer}
 \usepackage{../slides}
 \usepackage{../langs}
-\usepackage{../data}
 \usepackage{../graphics}
 \usepackage{../grammar}
 \usepackage{soul}
+\usepackage{mathpartir}
-\tikzset{onslide/.code args={<#1>#2}{%
-\only<#1>{\pgfkeysalso{#2}} % \pgfkeysalso doesn't change the path
+% beamer stuff
-}}
-\makeatletter
-\newenvironment<>{btHighlight}[1][]
-{\begin{onlyenv}#2\begingroup\tikzset{bt@Highlight@par/.style={#1}}\begin{lrbox}{\@tempboxa}}
-{\end{lrbox}\bt@HL@box[bt@Highlight@par]{\@tempboxa}\endgroup\end{onlyenv}}
-\newcommand<>\btHL[1][]{%
-\only#2{\begin{btHighlight}[#1]\bgroup\aftergroup\bt@HL@endenv}%
-}
-\def\bt@HL@endenv{%b jm
-\end{btHighlight}%
-\egroup
-}
-\newcommand{\bt@HL@box}[2][]{%
-\tikz[#1]{%
-\pgfpathrectangle{\pgfpoint{1pt}{0pt}}{\pgfpoint{\wd #2}{\ht #2}}%
-\pgfusepath{use as bounding box}%
-\node[anchor=base west, fill=orange!30,outer sep=0pt,inner xsep=1pt, inner ysep=0pt, rounded corners=3pt, minimum height=\ht\strutbox+1pt,#1]{\raisebox{1pt}{\strut}\strut\usebox{#2}};
-}%
-}
-\makeatother
-\lstset{morekeywords={def,if,then,else,write,read},keywordstyle=\color{codepurple}\bfseries}
-% beamer stuff
 \renewcommand{\slidecaption}{CFL 09, King's College London}
 \newcommand{\bl}[1]{\textcolor{blue}{#1}}
 \begin{document}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[t]
 \frametitle{%
 \begin{tabular}{@ {}c@ {}}
 \\[-3mm]
 \LARGE Compilers and \\[-2mm]
-\LARGE Formal Languages (8)\\[3mm]
+\LARGE Formal Languages (9)\\[3mm]
 \end{tabular}}
 \normalsize
 \begin{center}
 \begin{tabular}{ll}
 Email:  & christian.urban at kcl.ac.uk\\
 Office: & N7.07 (North Wing, Bush House)\\
 Slides: & KEATS (also home work is there)\\
 \end{tabular}
 \end{center}
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[t,fragile]
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\frametitle{Compiling AExps}
+\begin{frame}[c]
-For example \bl{$1 + ((2 * 3) + (4 - 3))$}:\medskip
+\begin{center}
+\includegraphics[scale=0.6]{../pics/bridge-limits.png}
-\begin{columns}[T]
+\end{center}
-\begin{column}{.3\textwidth}
-\begin{center}
+\end{frame}
-\bl{\begin{tikzpicture}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\tikzset{level distance=12mm,sibling distance=4mm}
-\tikzset{edge from parent/.style={draw,very thick}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\Tree [.$+$ [.$1$ ] [.$+$ [.$*$ $2$ $3$ ] [.$-$ $4$ $3$ ]]]
+\begin{frame}[c]
-\end{tikzpicture}}
+\frametitle{Old-Fashioned Eng.~vs.~CS}
-\end{center}
-\end{column}
+\begin{center}
-\begin{column}{.3\textwidth}
+\begin{tabular}{@{}cc@{}}
-\begin{lstlisting}[language=JVMIS,numbers=none]
+\begin{tabular}{@{}p{5.2cm}}
-ldc 1
+\includegraphics[scale=0.058]{../pics/towerbridge.jpg}\\
-ldc 2
+{\bf bridges}: \\
-ldc 3
+\raggedright\small
-imul
+engineers can ``look'' at a bridge and have a pretty good
-ldc 4
+intuition about whether it will hold up or not\\
-ldc 3
+(redundancy; predictive theory)
-isub
+\end{tabular} &
-iadd
+\begin{tabular}{p{5cm}}
-iadd
+\includegraphics[scale=0.265]{../pics/code.jpg}\\
-\end{lstlisting}
+\raggedright
-\end{column}
+{\bf code}: \\
-\end{columns}\bigskip
+\raggedright\small
+programmers have very little intuition about their code;
-\small
+often it is too expensive to have redundancy;
-Traverse tree in post-order \bl{$\Rightarrow$} code for
+not ``continuous''
-stack-machine
+\end{tabular}
+\end{tabular}
-\end{frame}
+\end{center}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c,fragile]
-\frametitle{Compiling AExps}
-\bl{
-\begin{center}
-\begin{tabular}{lcl}
-$\textit{compile}(n, E)$ & $\dn$ & $\pcode{ldc}\;n$\smallskip\\
-$\textit{compile}(a_1 + a_2, E)$ & $\dn$ \\
-\multicolumn{3}{c}{$\qquad\textit{compile}(a_1, E) \;@\;\textit{compile}(a_2, E)\;@\; \pcode{iadd}$}\smallskip\\
-$\textit{compile}(a_1 - a_2, E)$ & $\dn$ \\
-\multicolumn{3}{c}{$\qquad\textit{compile}(a_1, E) \;@\; \textit{compile}(a_2, E)\;@\; \pcode{isub}$}\smallskip\\
-$\textit{compile}(a_1 * a_2, E)$ & $\dn$ \\
-\multicolumn{3}{c}{$\qquad\textit{compile}(a_1, E) \;@\; \textit{compile}(a_2, E)\;@\; \pcode{imul}$}\smallskip\\
-$\textit{compile}(a_1 \backslash a_2, E)$ & $\dn$\\
-\multicolumn{3}{c}{$\qquad\textit{compile}(a_1, E) \;@\; \textit{compile}(a_2, E)\;@\; \pcode{idiv}$}\smallskip\\
-$\textit{compile}(x, E)$ & $\dn$ & $\pcode{iload}\;E(x)$\\
-\end{tabular}
-\end{center}}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c,fragile]
-\frametitle{Compiling Ifs}
-For example
-\begin{lstlisting}[mathescape,numbers=none,language=While]
-if 1 = 1 then x := 2 else y := 3
-\end{lstlisting}
-\begin{center}
-\begin{lstlisting}[mathescape,language=JVMIS,numbers=none]
-ldc 1
-ldc 1
-if_icmpne L_ifelse $\quad\tikz[remember picture] \node (C) {\mbox{}};$
-ldc 2
-istore 0
-goto L_ifend $\quad\tikz[remember picture] \node (A) {\mbox{}};$
-L_ifelse: $\quad\tikz[remember picture] \node[] (D) {\mbox{}};$
-ldc 3
-istore 1
-L_ifend: $\quad\tikz[remember picture] \node[] (B) {\mbox{}};$
-\end{lstlisting}
-\end{center}
-\begin{tikzpicture}[remember picture,overlay]
-\draw[->,very thick] (A) edge [->,to path={-- ++(10mm,0mm)
--- ++(0mm,-17.3mm) |- (\tikztotarget)},line width=1mm] (B.east);
-\draw[->,very thick] (C) edge [->,to path={-- ++(10mm,0mm)
--- ++(0mm,-17.3mm) |- (\tikztotarget)},line width=1mm] (D.east);
-\end{tikzpicture}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c,fragile]
-\frametitle{Compiling Whiles}
-For example
-\begin{lstlisting}[mathescape,numbers=none,language=While]
-while x <= 10 do x := x + 1
-\end{lstlisting}
-\begin{center}
-\begin{lstlisting}[mathescape,language=JVMIS,numbers=none]
-L_wbegin: $\quad\tikz[remember picture] \node[] (LB) {\mbox{}};$
-iload 0
-ldc 10
-if_icmpgt L_wend $\quad\tikz[remember picture] \node (LC) {\mbox{}};$
-iload 0
-ldc 1
-iadd
-istore 0
-goto L_wbegin $\quad\tikz[remember picture] \node (LA) {\mbox{}};$
-L_wend: $\quad\tikz[remember picture] \node[] (LD) {\mbox{}};$
-\end{lstlisting}
-\end{center}
-\begin{tikzpicture}[remember picture,overlay]
-\draw[->,very thick] (LA) edge [->,to path={-- ++(12mm,0mm)
--- ++(0mm,17.3mm) |- (\tikztotarget)},line width=1mm] (LB.east);
-\draw[->,very thick] (LC) edge [->,to path={-- ++(12mm,0mm)
--- ++(0mm,-17.3mm) |- (\tikztotarget)},line width=1mm] (LD.east);
-\end{tikzpicture}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c,fragile]
-\frametitle{Compiling Writes}
-\small
-\begin{lstlisting}[language=JVMIS,mathescape,
-numbers=none,xleftmargin=-6mm]
-.method public static write(I)V
-.limit locals 1
-.limit stack 2
-getstatic java/lang/System/out
-Ljava/io/PrintStream;
-iload 0
-invokevirtual java/io/PrintStream/println(I)V
-return
-.end method
-iload $E(x)$
-invokestatic XXX/XXX/write(I)V
-\end{lstlisting}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c,fragile]
-\frametitle{Compiling Main}
-\footnotesize
-\begin{lstlisting}[language=JVMIS,mathescape,
-numbers=none,xleftmargin=-6mm]
-.class public XXX.XXX
-.super java/lang/Object
-.method public <init>()V
-aload_0
-invokenonvirtual java/lang/Object/<init>()V
-return
-.end method
-.method public static main([Ljava/lang/String;)V
-.limit locals 200
-.limit stack 200
-$\textit{\ldots{}here comes the compiled code\ldots}$
-return
-.end method
-\end{lstlisting}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c,fragile]
-\frametitle{Functional Programming}
-\footnotesize
-\begin{textblock}{13}(0.9,3)
-\begin{lstlisting}[]numbers=none]
-def fib(n) = if n == 0 then 0
-else if n == 1 then 1
-else fib(n - 1) + fib(n - 2);
-def fact(n) = if n == 0 then 1 else n * fact(n - 1);
-def ack(m, n) = if m == 0 then n + 1
-else if n == 0 then ack(m - 1, 1)
-else ack(m - 1, ack(m, n - 1));
-def gcd(a, b) = if b == 0 then a else gcd(b, a % b);
-\end{lstlisting}
-\end{textblock}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c]
-\frametitle{Fun Grammar}
-\bl{
-\begin{plstx}[rhs style=]
-: \meta{Exp} ::= \meta{Var} | \meta{Num}{\hspace{3cm}}
-|   \meta{Exp} + \meta{Exp} | ... | (\meta{Exp})
-|   \code{if} \meta{BExp} \code{then} \meta{Exp} \code{else} \meta{Exp}
-|   \code{write} \meta{Exp} {\hspace{3cm}}
-|   \meta{Exp} ; \meta{Exp}
-|   \textit{FunName} (\meta{Exp}, ... , \meta{Exp})\\
-: \meta{BExp} ::= ...\\
-: \meta{Decl} ::= \meta{Def} ; \meta{Decl}
-| \meta{Exp}\\
-: \meta{Def} ::= \code{def} \textit{FunName} ($\hspace{0.4mm}x_1$, ... , $x_n$) = \meta{Exp}\\
-\end{plstx}}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c, fragile]
-\frametitle{Abstract Syntax Trees}
-\footnotesize
-\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-1mm]
-abstract class Exp
-abstract class BExp
-abstract class Decl
-case class Var(s: String) extends Exp
-case class Num(i: Int) extends Exp
-case class Aop(o: String, a1: Exp, a2: Exp) extends Exp
-case class If(a: BExp, e1: Exp, e2: Exp) extends Exp
-case class Write(e: Exp) extends Exp
-case class Sequ(e1: Exp, e2: Exp) extends Exp
-case class Call(name: String, args: List[Exp]) extends Exp
-case class Bop(o: String, a1: Exp, a2: Exp) extends BExp
-case class Def(name: String,
-args: List[String],
-body: Exp) extends Decl
-case class Main(e: Exp) extends Decl
-\end{lstlisting}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c, fragile]
-\frametitle{Sequences}
-Compiling \texttt{exp1 ; exp2}:\bigskip
-\begin{lstlisting}[mathescape,language=JVMIS, numbers=none]
-$\textit{compile}$(exp1)
-pop
-$\textit{compile}$(exp2)
-\end{lstlisting}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c, fragile]
-\frametitle{Write}
-Compiling call to \texttt{write(1+2)}:\bigskip
-\begin{lstlisting}[mathescape,language=JVMIS, numbers=none]
-$\textit{compile}$(1+2)
-dup
-invokestatic XXX/XXX/write(I)V
-\end{lstlisting}\bigskip
-\small
-needs the helper method
-\footnotesize
-\begin{lstlisting}[language=JVMIS,
-xleftmargin=2mm,
-numbers=none]
-.method public static write(I)V
-.limit locals 1
-.limit stack 2
-getstatic java/lang/System/out Ljava/io/PrintStream;
-iload 0
-invokevirtual java/io/PrintStream/println(I)V
-return
-.end method
-\end{lstlisting}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[t, fragile]
-\frametitle{Function Definitions}
-\footnotesize
-\begin{lstlisting}[language=JVMIS,
-xleftmargin=2mm,
-numbers=none]
-.method public static write(I)V
-.limit locals 1
-.limit stack 2
-getstatic java/lang/System/out Ljava/io/PrintStream;
-iload 0
-invokevirtual java/io/PrintStream/println(I)V
-return
-.end method
-\end{lstlisting}\bigskip
-\small We will need for definitions, like\footnotesize\medskip
-\begin{lstlisting}[language=JVMIS,
-xleftmargin=2mm,
-numbers=none]
-def fname (x1, ... , xn) = ...
-.method public static fname (I...I)I
-.limit locals ??
-.limit stack ??
-??
-.end method
-\end{lstlisting}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c, fragile]
-\frametitle{Stack Estimation}
-\small
-\mbox{}\\[-15mm]
-\bl{\begin{center}
-\begin{tabular}{@{\hspace{-4mm}}l@{\hspace{2mm}}c@{\hspace{2mm}}l@{}}
-$\textit{estimate}(n)$ & $\dn$ & $1$\\
-$\textit{estimate}(x)$ & $\dn$ & $1$\\
-$\textit{estimate}(a_1\;aop\;a_2)$ & $\dn$ &
-$\textit{estimate}(a_1) + \textit{estimate}(a_2)$\\
-$\textit{estimate}(\pcode{if}\;b\;\pcode{then}\;e_1\;\pcode{else}\;e_2)$ & $\dn$ &
-$\textit{estimate}(b) +$\\
-& & $\quad max(\textit{estimate}(e_1), \textit{estimate}(e_2))$\\
-$\textit{estimate}(\pcode{write}(e))$ & $\dn$ &
-$\textit{estimate}(e) + 1$\\
-$\textit{estimate}(e_1 ; e_2)$ & $\dn$ &
-$max(\textit{estimate}(e_1), \textit{estimate}(e_2))$\\
-$\textit{estimate}(f(e_1, ..., e_n))$ & $\dn$ &
-$\sum_{i = 1..n}\;estimate(e_i)$\medskip\\
-$\textit{estimate}(a_1\;bop\;a_2)$ & $\dn$ &
-$\textit{estimate}(a_1) + \textit{estimate}(a_2)$\\
-\end{tabular}
-\end{center}}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[fragile]
-\frametitle{Successor Function}
-\begin{textblock}{7}(1,2.5)\footnotesize
-\begin{minipage}{6cm}
-\begin{lstlisting}[language=JVMIS,basicstyle=\ttfamily, numbers=none]
-.method public static suc(I)I
-.limit locals 1
-.limit stack 2
-iload 0
-ldc 1
-iadd
-ireturn
-.end method
-\end{lstlisting}
-\end{minipage}
-\end{textblock}
-\begin{textblock}{7}(6,8)
-\begin{bubble}[5cm]\small
-\begin{lstlisting}[language=Lisp,
-basicstyle=\ttfamily,
-numbers=none,
-xleftmargin=1mm]
-def suc(x) = x + 1;
-\end{lstlisting}
-\end{bubble}
-\end{textblock}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[fragile]
-\frametitle{Addition Function}
-\begin{textblock}{7}(1,1.9)\footnotesize
-\begin{minipage}{6cm}
-\begin{lstlisting}[language=JVMIS,basicstyle=\ttfamily, numbers=none]
-.method public static add(II)I
-.limit locals 2
-.limit stack 5
-iload 0
-ldc 0
-if_icmpne If_else
-iload 1
-goto If_end
-If_else:
-iload 0
-ldc 1
-isub
-iload 1
-invokestatic XXX/XXX/add(II)I
-invokestatic XXX/XXX/suc(I)I
-If_end:
-ireturn
-.end method
-\end{lstlisting}
-\end{minipage}
-\end{textblock}
-\begin{textblock}{7}(6,6.6)
-\begin{bubble}[7cm]\small
-\begin{lstlisting}[language=Lisp,
-basicstyle=\ttfamily,
-numbers=none,
-xleftmargin=1mm]
-def add(x, y) =
-if x == 0 then y
-else suc(add(x - 1, y));
-\end{lstlisting}
-\end{bubble}
-\end{textblock}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[fragile]
-\frametitle{Factorial}
-\begin{textblock}{7}(1,1.5)\footnotesize
-\begin{minipage}{6cm}
-\begin{lstlisting}[language=JVMIS,basicstyle=\ttfamily, numbers=none]
-.method public static facT(II)I
-.limit locals 2
-.limit stack 6
-iload 0
-ldc 0
-if_icmpne If_else_2
-iload 1
-goto If_end_3
-If_else_2:
-iload 0
-ldc 1
-isub
-iload 0
-iload 1
-imul
-invokestatic fact/fact/facT(II)I
-If_end_3:
-ireturn
-.end method
-\end{lstlisting}
-\end{minipage}
-\end{textblock}
-\begin{textblock}{7}(6,7)
-\begin{bubble}[7cm]\small
-\begin{lstlisting}[language=Lisp,
-basicstyle=\ttfamily,
-numbers=none,
-xleftmargin=1mm]
-def facT(n, acc) =
-if n == 0 then acc
-else facT(n - 1, n * acc);
-\end{lstlisting}
-\end{bubble}
-\end{textblock}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[fragile]
-\begin{textblock}{7}(1,-0.2)\footnotesize
-\begin{minipage}{6cm}
-\begin{lstlisting}[language=JVMIS,basicstyle=\ttfamily, numbers=none, escapeinside={(*@}{@*)}]
-.method public static facT(II)I
-.limit locals 2
-.limit stack 6
-(*@\hl{facT\_Start:} @*)
-iload 0
-ldc 0
-if_icmpne If_else_2
-iload 1
-goto If_end_3
-If_else_2:
-iload 0
-ldc 1
-isub
-iload 0
-iload 1
-imul
-(*@\hl{istore 1} @*)
-(*@\hl{istore 0} @*)
-(*@\hl{goto facT\_Start} @*)
-If_end_3:
-ireturn
-.end method
-\end{lstlisting}
-\end{minipage}
-\end{textblock}
-\begin{textblock}{7}(6,7)
-\begin{bubble}[7cm]\small
-\begin{lstlisting}[language=Lisp,
-basicstyle=\ttfamily,
-numbers=none,
-xleftmargin=1mm]
-def facT(n, acc) =
-if n == 0 then acc
-else facT(n - 1, n * acc);
-\end{lstlisting}
-\end{bubble}
-\end{textblock}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c, fragile]
-\frametitle{Tail Recursion}
-A call to \texttt{f(args)} is usually compiled as\medskip
-{\small\begin{lstlisting}[basicstyle=\ttfamily, numbers=none]
-args onto stack
-invokestatic  .../f
-\end{lstlisting}}\pause
-A call is in tail position provided:\medskip
-{\small\begin{itemize}
-\item \texttt{if Bexp then \hl{Exp} else \hl{Exp}}
-\item \texttt{Exp ; \hl{Exp}}
-\item \texttt{Exp  op Exp}
-\end{itemize}}\medskip
-then a call \texttt{f(args)} can be compiled as\medskip\small
-\begin{lstlisting}[basicstyle=\ttfamily, numbers=none]
-prepare environment
-jump to start of function
-\end{lstlisting}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[c, fragile]
-\frametitle{Tail Recursive Call}
-\footnotesize
-\begin{textblock}{13}(-0.3,2)
-\begin{lstlisting}[language=Scala,basicstyle=\ttfamily, numbers=none]
-def compile_expT(a: Exp, env: Mem, name: String): Instrs =
-...
-case Call(n, args) => if (name == n)
-{
-val stores = args.zipWithIndex.map
-{ case (x, y) => "istore " + y.toString + "\n" }
-args.flatMap(a => compile_expT(a, env, "")) ++
-stores.reverse ++
-List ("goto " + n + "_Start\n")
-}
-else
-{
-val is = "I" * args.length
-args.flatMap(a => compile_expT(a, env, "")) ++
-List ("invokestatic XXX/XXX/" + n + "(" + is + ")I\n")
-}
-\end{lstlisting}
-\end{textblock}
-\end{frame}
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
 \frametitle{Dijkstra on Testing}
 \begin{bubble}[10cm]
 ``Program testing can be a very effective way to show the
 presence of bugs, but it is hopelessly inadequate for showing
 their absence.''
 \end{bubble}\bigskip
-\small
-What is good about compilers: the either seem to work,
-or go horribly wrong (most of the time).
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
 {\bf Long, long proof} \ldots\\
 \end{bubble}\bigskip\medskip
 \small This can be a gigantic proof. The only hope is to have
 help from the computer. `Program' is here to be understood to be
-quite general (compiler, OS, \ldots).
+quite general (protocols, OS, \ldots).
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{\Large{}Mars Pathfinder Mission 1997}
+\begin{center}
+\includegraphics[scale=0.15]{../pics/marspath1.png}
+\includegraphics[scale=0.16]{../pics/marspath3.png}
+\includegraphics[scale=0.3]{../pics/marsrover.png}
+\end{center}
+\begin{itemize}
+\item despite NASA's famous testing procedures, the lander crashed frequently on Mars
+\item a scheduling algorithm was not used in the OS
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\begin{textblock}{11}(1,3)
+\begin{tabular}{@{\hspace{-10mm}}l}
+\begin{tikzpicture}[scale=1.1]
+\node at (-2.5,-1.5) {\textcolor{white}{a}};
+\node at (8,4) {\textcolor{white}{a}};
+\only<1>{
+\draw[fill, blue!50] (1,0) rectangle (3,0.6);
+}
+\only<2>{
+\draw[fill, blue!50] (1,0) rectangle (2,0.6);
+\draw[fill, blue!50] (3,0) rectangle (5,0.6);
+\draw[fill, blue!100] (2,3) rectangle (3,3.6);
+}
+\only<3>{
+\draw[fill, blue!50] (1,0) rectangle (2,0.6);
+\draw[fill, blue!50] (3,0) rectangle (4.5,0.6);
+\draw[fill, blue!50] (5.5,0) rectangle (6,0.6);
+\draw[fill, blue!100] (2,3) rectangle (3,3.6);
+\draw[fill, blue!100] (4.5,3) rectangle (5.5,3.6);
+}
+\only<4>{
+\node at (2.5,0.9) {\small locked a resource};
+\draw[fill, blue!50] (1,0) rectangle (2,0.6);
+\draw[blue!50, very thick] (2,0) rectangle (4,0.6);
+\draw[blue!100, very thick] (2,3) rectangle (3, 3.6);
+\draw[red, <-, line width = 2mm] (2,-0.1) -- (2, -1);
+}
+\only<5>{
+\node at (2.5,0.9) {\small locked a resource};
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+\draw[very thick,->](0,0) -- (8,0);
+\node [anchor=base] at (8, -0.3) {\scriptsize time};
+\node [anchor=base] at (0, -0.3) {\scriptsize 0};
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+\only<2->{\node [anchor=base] at (-1.2, 3.2) {\small high priority};}
+\only<8->{\node [anchor=base] at (-1.5, 1.7) {\small medium pr.};}
+\end{tikzpicture}
+\end{tabular}
+\end{textblock}
+\begin{textblock}{0}(2.5,13)%
+\small
+\onslide<3->{
+\begin{bubble}[8cm]%
+Scheduling: You want to avoid that a high
+priority process is starved indefinitely.
+\end{bubble}}
+\end{textblock}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{\Large Priority Inheritance Scheduling}
+\begin{itemize}
+\item Let a low priority process $L$ temporarily inherit
+the high priority of $H$ until $L$ leaves the critical
+section unlocking the resource.\bigskip
+\item Once the resource is unlocked $L$ returns to its original
+priority level.
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\begin{textblock}{11}(1,3)
+\begin{tabular}{@{\hspace{-10mm}}l}
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+\draw[very thick,blue!100] (2.0,0) -- (2.0,0.6);
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+\draw[very thick,blue!100] (7,3) rectangle (8,3.6);
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+\draw[red, fill] (5,1.5) rectangle (6,2.1);
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+\draw[blue!50, ->, line width = 2mm] (7.1,0.4) -- (8, 0.4);
+\draw[blue!50, ->, line width = 2mm] (7.1,4) -- (8,4);
+}
+\draw[very thick,->](0,0) -- (8,0);
+\node [anchor=base] at (8, -0.3) {\scriptsize time};
+\node [anchor=base] at (0, -0.3) {\scriptsize 0};
+\node [anchor=base] at (-1.2, 0.2) {\small low priority};
+\only<2->{\node [anchor=base] at (-1.2, 3.2) {\small high priority};}
+\only<10->{\node [anchor=base] at (-1.5, 1.7) {\small medium pr.};}
+\end{tikzpicture}
+\end{tabular}
+\end{textblock}
+\begin{textblock}{0}(2.5,13)%
+\small
+\onslide<11>{
+\begin{bubble}[8cm]%
+Scheduling: You want to avoid that a high
+priority process is staved indefinitely.
+\end{bubble}}
+\end{textblock}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{\Large Priority Inheritance Scheduling}
+\begin{itemize}
+\item Let a low priority process $L$ temporarily inherit
+the high priority of $H$ until $L$ leaves the critical
+section unlocking the resource.\bigskip
+\item Once the resource is unlocked $L$ returns to its original
+priority level. \alert{\bf BOGUS}\pause\bigskip
+\item \ldots $L$ needs to switch to the highest
+\alert{remaining} priority of the threads that it blocks.
+\end{itemize}\bigskip
+\small this error is already known since around 1999
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\begin{center}
+\includegraphics[scale=0.25]{../pics/p3.jpg}
+\end{center}
+\begin{itemize}
+\item by Rajkumar, 1991
+\item \it ``it resumes the priority it had at the point of entry into the critical
+section''
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\begin{center}
+\includegraphics[scale=0.25]{../pics/p2.jpg}
+\end{center}
+\begin{itemize}
+\item by Jane Liu, 2000
+\item {\it ``The job $J_l$ executes at its inherited
+priority until it releases $R$; at that time, the
+priority of $J_l$ returns to its priority
+at the time when it acquires the resource $R$.''}\medskip
+\item \small gives pseudo code and totally bogus data structures
+\item \small interesting part ``{\it left as an exercise}''
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\begin{center}
+\includegraphics[scale=0.15]{../pics/p1.pdf}
+\end{center}
+\begin{itemize}
+\item by Laplante and Ovaska, 2011 (\$113.76)
+\item \it ``when $[$the task$]$ exits the critical section that
+caused the block, it reverts to the priority it had
+when it entered that section''
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\begin{center}
+\includegraphics[scale=0.25]{../pics/p4.jpg}
+\end{center}
+\begin{itemize}
+\item by Silberschatz, Galvin, and Gagne, 2013 (OS-bible)
+\item \it ``Upon releasing the lock, the
+$[$low-priority$]$ thread will revert to
+its original priority.''
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{Priority Scheduling}
+\begin{itemize}
+\item a scheduling algorithm that is widely used in real-time operating systems
+\item has been ``proved'' correct by hand in a paper in 1983
+\item but this algorithm turned out to be incorrect, despite its ``proof''\bigskip\pause
+\item we used the corrected algorithm and then {\bf really} proved
+that it is correct
+\item we implemented this algorithm in a small OS called PINTOS
+(used for teaching at Stanford)
+\item our implementation was much more efficient than their
+reference implementation
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
-\frametitle{Can This Be Done?}
+\frametitle{Big Proofs in CS (1)}
+Formal proofs in CS sound like science fiction?
 \begin{itemize}
-\item in 2008, verification of a small C-compiler
+\item in 2008, verification of a C-compiler
 \begin{itemize}
 \item ``if my input program has a certain behaviour, then the compiled machine code has the same behaviour''
-\item is as good as \texttt{gcc -O1}, but much, much less buggy
+\item is as good as \texttt{gcc -O1}, but much less buggy
 \end{itemize}
 \end{itemize}
 \begin{center}
 \includegraphics[scale=0.12]{../pics/compcert.png}
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% \begin{frame}[c]
+% \frametitle{Fuzzy Testing C-Compilers}
+% \begin{itemize}
+% \item tested GCC, LLVM and others by randomly generating
+% C-programs
+% \item found more than 300 bugs in GCC and also
+% many in LLVM (some of them highest-level critical)\bigskip
+% \item about CompCert:
+% \begin{bubble}[10cm]\small ``The striking thing about our CompCert
+% results is that the middle-end bugs we found in all other
+% compilers are absent. As of early 2011, the under-development
+% version of CompCert is the only compiler we have tested for
+% which Csmith cannot find wrong-code errors. This is not for
+% lack of trying: we have devoted about six CPU-years to the
+% task.''
+% \end{bubble}
+% \end{itemize}
+% \end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
-\frametitle{Fuzzy Testing C-Compilers}
+\frametitle{Big Proofs in CS (2)}
 \begin{itemize}
-\item tested GCC, LLVM and others by randomly generating
+\item in 2010, verification of a micro-kernel operating system (approximately 8700 loc)
-C-programs
+\begin{itemize}
-\item found more than 300 bugs in GCC and also
+\item used in helicopters and mobile phones
-many in LLVM (some of them highest-level critical)\bigskip
+\item 200k loc of proof
-\item about CompCert:
+\item 25 - 30 person years
+\item found 160 bugs in the C code (144 by the proof)
-\begin{bubble}[10cm]\small ``The striking thing about our CompCert
+\end{itemize}
-results is that the middle-end bugs we found in all other
-compilers are absent. As of early 2011, the under-development
-version of CompCert is the only compiler we have tested for
-which Csmith cannot find wrong-code errors. This is not for
-lack of trying: we have devoted about six CPU-years to the
-task.''
-\end{bubble}
 \end{itemize}
-\end{frame}
+\begin{bubble}[10cm]\small
+``Real-world operating-system kernel with an end-to-end proof
+of implementation correctness and security enforcement''
+\end{bubble}\bigskip\pause
+unhackable kernel (New Scientists, September 2015)
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{Big Proofs in CS (3)}
+\begin{itemize}
+\item verified TLS implementation\medskip
+\item verified compilers (CompCert, CakeML)\medskip
+\item verified distributed systems (Verdi)\medskip
+\item verified OSes or OS components\\
+(seL4, CertiKOS, \ldots)\bigskip\pause
+\item Infer static analyser developed by Facebook
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{How Did This Happen?}
+Lots of ways!
+\begin{itemize}
+\item better programming languages
+\begin{itemize}
+\item basic safety guarantees built in
+\item powerful mechanisms for abstraction and modularity
+\end{itemize}
+\item better software development methodology
+\item stable platforms and frameworks
+\item better use of specifications\medskip\\
+\small If you want to build software that works or is secure,
+it is helpful to know what you mean by ``works'' and by ``is secure''!
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{Goal}
+Remember the Bridges example?
+\begin{itemize}
+\item Can we look at our programs and somehow ensure
+they are bug free/correct?\pause\bigskip
+\item Very hard: Anything interesting about programs is equivalent
+to the Halting Problem, which is undecidable.\pause\bigskip
+\item \alert{Solution:} We avoid this ``minor'' obstacle by
+being as close as possible of deciding the halting
+problem, without actually deciding the halting problem.
+\small$\quad\Rightarrow$ yes, no, don't know (static analysis)
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{What is Static Analysis?}
+\begin{center}
+\includegraphics[scale=0.4]{../pics/state.png}
+\end{center}
+\begin{itemize}
+\item depending on some initial input, a program
+(behaviour) will ``develop'' over time.
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{What is Static Analysis?}
+\begin{center}
+\includegraphics[scale=0.4]{../pics/state2.png}
+\end{center}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{What is Static Analysis?}
+\begin{center}
+\includegraphics[scale=0.4]{../pics/state3.jpg}
+\end{center}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{What is Static Analysis?}
+\begin{center}
+\includegraphics[scale=0.4]{../pics/state4.jpg}
+\end{center}
+\begin{itemize}
+\item to be avoided
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{What is Static Analysis?}
+\begin{center}
+\includegraphics[scale=0.4]{../pics/state5.png}
+\end{center}
+\begin{itemize}
+\item this needs more work
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{What is Static Analysis?}
+\begin{center}
+\includegraphics[scale=0.4]{../pics/state6.png}
+\end{center}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{\Large\begin{tabular}{c}Concrete Example:\\[-1mm]
+Are Vars Definitely Initialised?\end{tabular}}
+Assuming \texttt{x} is initialised, what about \texttt{y}?\bigskip
+Prog.~1:\\
+\begin{lstlisting}[numbers=none,
+basicstyle=\ttfamily,
+language=While,xleftmargin=3mm]
+if x < 1 then y := x else y := x + 1;
+y := y + 1
+\end{lstlisting}\medskip
+Prog.~2:\\
+\begin{lstlisting}[numbers=none,
+basicstyle=\ttfamily,
+language=While,xleftmargin=3mm]
+if x < x then y := y + 1 else y := x;
+y := y + 1
+\end{lstlisting}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{\Large\begin{tabular}{c}Concrete Example:\\[-1mm]
+Are Vars Definitely Initialised?\end{tabular}}
+What should the rules be for deciding when a
+variable is initialised?\bigskip\pause
+\begin{itemize}
+\item variable \texttt{x} is definitely initialized after
+\texttt{skip}\\
+iff \texttt{x} is definitely initialized before \texttt{skip}.
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+%    \frametitle{\Large\begin{tabular}{c}Concrete Example:\\[-1mm]
+%                  Are Vars Definitely Initialised?\end{tabular}}
+$\bl{A}$ is the set of definitely defined variables:
+\begin{center}
+\begin{tabular}{c}
+\bl{\infer{\mbox{}}{A\;\texttt{skip}\;A}}\qquad
+\bl{\infer{vars(a) \subseteq A}{A\;\;(\texttt{x\,:=\,a})\;\;\{x\}\cup A}}
+\medskip\\\pause
+\bl{\infer{A_1\;s_1\;A_2\quad A_2\;s_2\;A_3}{A_1\;(s_1 ; s_2)\;A_3}}
+\medskip\\\pause
+\bl{\infer{vars(b)\subseteq A\quad A\;s_1\;A_1\quad A\;s_2\;A_2}
+{A\;(\texttt{if}\;b\;\texttt{then}\;s_1\;\texttt{else}\;s_2)\;A_1\cap A_2}}
+\medskip\\\pause
+\bl{\infer{vars(b)\subseteq A\quad A\;s\;A'}
+{A\;(\texttt{while}\;b\;\texttt{do}\;s)\;A}}\pause
+\end{tabular}
+\end{center}
+\hfill we start with $\bl{A = \{\}}$
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{\large Concrete Example: Sign-Analysis}
+\mbox{}\\[-20mm]\mbox{}
+\bl{\begin{plstx}[rhs style=,one per line]
+: \meta{Exp} ::= \meta{Exp} + \meta{Exp}
+| \meta{Exp} * \meta{Exp}
+| \meta{Exp} = \meta{Exp}
+| \meta{num}
+| \meta{var}\\
+: \meta{Stmt} ::= \meta{label} :
+| \meta{var} := \meta{Exp}
+| \pcode{jmp?} \meta{Exp} \meta{label}
+| \pcode{goto} \meta{label}\\
+: \meta{Prog} ::= \meta{Stmt} \ldots{} \meta{Stmt}\\
+\end{plstx}}
+\begin{textblock}{0}(7.8,2.5)
+\small
+\begin{bubble}[5.6cm]
+\begin{lstlisting}[numbers=none,
+basicstyle=\ttfamily,
+language={},xleftmargin=3mm]
+a := 1
+n := 5
+top:  jmp? n = 0 done
+a := a * n
+n := n + -1
+goto top
+done:
+\end{lstlisting}
+\end{bubble}
+\end{textblock}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{\large Concrete Example: Sign-Analysis}
+\mbox{}\\[-20mm]\mbox{}
+\bl{\begin{plstx}[rhs style=,one per line]
+: \meta{Exp} ::= \meta{Exp} + \meta{Exp}
+| \meta{Exp} * \meta{Exp}
+| \meta{Exp} = \meta{Exp}
+| \meta{num}
+| \meta{var}\\
+: \meta{Stmt} ::= \meta{label} :
+| \meta{var} := \meta{Exp}
+| \pcode{jmp?} \meta{Exp} \meta{label}
+| \pcode{goto} \meta{label}\\
+: \meta{Prog} ::= \meta{Stmt} \ldots{} \meta{Stmt}\\
+\end{plstx}}
+\begin{textblock}{0}(7.8,3.5)
+\small
+\begin{bubble}[5.6cm]
+\begin{lstlisting}[numbers=none,
+basicstyle=\ttfamily,
+language={},xleftmargin=3mm]
+n := 6
+m1 := 0
+m2 := 1
+top:  jmp? n = 0 done
+tmp := m2
+m2 := m1 + m2
+m1 := tmp
+n := n + -1
+goto top
+done:
+\end{lstlisting}
+\end{bubble}
+\end{textblock}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{\large Concrete Example: Sign-Analysis}
+\mbox{}\\[-20mm]\mbox{}
+\bl{\begin{plstx}[rhs style=,one per line]
+: \meta{Exp} ::= \meta{Exp} + \meta{Exp}
+| \meta{Exp} * \meta{Exp}
+| \meta{Exp} = \meta{Exp}
+| \meta{num}
+| \meta{var}\\
+: \meta{Stmt} ::= \meta{label} :
+| \meta{var} := \meta{Exp}
+| \pcode{jmp?} \meta{Exp} \meta{label}
+| \pcode{goto} \meta{label}\\
+: \meta{Prog} ::= \meta{Stmt} \ldots{} \meta{Stmt}\\
+\end{plstx}}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{Eval: An Interpreter}
+\mbox{}\\[-14mm]\mbox{}
+\small
+\begin{center}
+\bl{\begin{tabular}{lcl}
+$[n]_{env}$ & $\dn$ & $n$\\
+$[x]_{env}$ & $\dn$ & $env(x)$\\
+$[e_1 + e_2]_{env}$ & $\dn$ & $[e_1]_{env} + [e_2]_{env}$\\
+$[e_1 * e_2]_{env}$ & $\dn$ & $[e_1]_{env} * [e_2]_{env}$\\
+$[e_1 = e_2]_{env}$ & $\dn$ &
+$\begin{cases}
+1 & \text{if}\quad[e_1]_{env} = [e_2]_{env}\\
+0 & \text{otherwise}
+\end{cases}$\\
+\end{tabular}}
+\end{center}
+\footnotesize
+\begin{lstlisting}[numbers=none,xleftmargin=-5mm]
+def eval_exp(e: Exp, env: Env) : Int = e match {
+case Num(n) => n
+case Var(x) => env(x)
+case Plus(e1, e2) => eval_exp(e1, env) + eval_exp(e2, env)
+case Times(e1, e2) => eval_exp(e1, env) * eval_exp(e2, env)
+case Equ(e1, e2) =>
+if (eval_exp(e1, env) == eval_exp(e2, env)) 1 else 0
+}
+\end{lstlisting}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\small
+A program
+\begin{bubble}[6cm]\footnotesize
+\begin{lstlisting}[numbers=none,
+language={},
+basicstyle=\ttfamily,
+xleftmargin=1mm]
+a := 1
+n := 5
+top:  jmp? n = 0 done
+a := a * n
+n := n + -1
+goto top
+done:
+\end{lstlisting}
+\end{bubble}
+The \emph{snippets} of the program:
+\footnotesize
+\begin{columns}
+\begin{column}[t]{5cm}
+\begin{bubble}[4.5cm]
+\begin{lstlisting}[numbers=none,
+basicstyle=\ttfamily,
+language={},xleftmargin=1mm]
+""    a := 1
+n := 5
+top:  jmp? n = 0 done
+a := a * n
+n := n + -1
+goto top
+done:
+\end{lstlisting}
+\end{bubble}
+\end{column}
+\begin{column}[t]{5cm}
+\begin{bubble}[4.5cm]
+\begin{lstlisting}[numbers=none,
+basicstyle=\ttfamily,
+language={},xleftmargin=1mm]
+top:  jmp? n = 0 done
+a := a * n
+n := n + -1
+goto top
+done:
+\end{lstlisting}
+\end{bubble}
+\end{column}
+\begin{column}[t]{2cm}
+\begin{bubble}[1.1cm]
+\begin{lstlisting}[numbers=none,
+basicstyle=\ttfamily,
+language={},xleftmargin=1mm]
+done:
+\end{lstlisting}
+\end{bubble}
+\end{column}
+\end{columns}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{Eval for Stmts}
+\mbox{}\\[-12mm]\mbox{}
+Let \bl{$sn$} be the snippets of a program
+\small
+\begin{center}
+\bl{\begin{tabular}{lcl}
+$[\texttt{nil}]_{env}$ & $\dn$ & $env$\medskip\\
+$[\texttt{Label}(l:)::rest]_{env}$ & $\dn$ & $[rest]_{env}$\medskip\\
+$[x \,\texttt{:=}\, a::rest]_{env}$ & $\dn$ &
+$[rest]_{(env[x:= [a]_{env}])}$\medskip\\
+$[\texttt{jmp?}\;b\;l::rest]_{env}$ & $\dn$ &
+$\begin{cases}
+[sn(l)]_{env} & \text{if}\quad[b]_{env} = true\\
+[rest]_{env}  & \text{otherwise}
+\end{cases}$\medskip\\
+$[\texttt{goto}\;l::rest]_{env}$ & $\dn$ & $[sn(l)]_{env}$\\
+\end{tabular}}
+\end{center}\bigskip
+Start with \bl{$[sn(\mbox{\code{""}})]_{\varnothing}$}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{Eval in Code}
+\footnotesize
+\begin{lstlisting}[language=Scala,numbers=none,xleftmargin=-5mm]
+def eval(sn: Snips) : Env = {
+def eval_stmts(sts: Stmts, env: Env) : Env = sts match {
+case Nil => env
+case Label(l)::rest => eval_stmts(rest, env)
+case Assign(x, e)::rest =>
+eval_stmts(rest, env + (x -> eval_exp(e, env)))
+case Jmp(b, l)::rest =>
+if (eval_exp(b, env) == 1) eval_stmts(sn(l), env)
+else eval_stmts(rest, env)
+case Goto(l)::rest => eval_stmts(sn(l), env)
+}
+eval_stmts(sn(""), Map())
+}
+\end{lstlisting}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{The Idea of Static Analysis}
+\small
+\mbox{}\bigskip\\
+\begin{columns}
+\begin{column}{5cm}
+\begin{bubble}[4.5cm]\footnotesize
+\begin{lstlisting}[numbers=none,
+language={},
+basicstyle=\ttfamily,
+xleftmargin=1mm]
+a := 1
+n := 5
+top:  jmp? n = 0 done
+a := a * n
+n := n + -1
+goto top
+done:
+\end{lstlisting}
+\end{bubble}
+\end{column}
+\begin{column}{1cm}
+\raisebox{-20mm}{\LARGE\bf$\Rightarrow$}
+\end{column}
+\begin{column}{6cm}
+\begin{bubble}[4.7cm]\footnotesize
+\begin{lstlisting}[numbers=none,
+language={},
+basicstyle=\ttfamily,
+xleftmargin=1mm,
+escapeinside={(*}{*)}]
+a := (*\hl{'+'}*)
+n := (*\hl{'+'}*)
+top:  jmp? n = (*\hl{'0'}*) done
+a := a * n
+n := n + (*\hl{'-'}*)
+goto top
+done:
+\end{lstlisting}
+\end{bubble}
+\end{column}
+\end{columns}\bigskip\bigskip
+Replace all constants and variables by either
+\pcode{+}, \pcode{-} or \pcode{0}. What we want to find out
+is what the sign of \texttt{a} and \texttt{n} is (they should
+always positive).
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{Sign Analysis?}
+\begin{columns}
+\begin{column}{3cm}
+\begin{tabular}{cc|l}
+$e_1$ & $e_2$ & $e_1 + e_2$\\\hline{}
+- & - & -\\
+- & 0 & -\\
+- & + & -, 0, +\\
+0 & $x$ & $x$\\
++ & - & -, 0, +\\
++ & 0 & +\\
++ & + & +\\
+\end{tabular}
+\end{column}
+\begin{column}{3cm}
+\begin{tabular}{cc|l}
+$e_1$ & $e_2$ & $e_1 * e_2$\\\hline{}
+- & - & +\\
+- & 0 & 0\\
+- & + & -\\
+0 & $x$ & 0\\
++ & - & -\\
++ & 0 & 0\\
++ & + & +\\
+\end{tabular}
+\end{column}
+\end{columns}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\mbox{}\\[-13mm]\mbox{}
+\small
+\begin{center}
+\bl{\begin{tabular}{lcl}
+$[n]_{aenv}$ & $\dn$ &
+$\begin{cases}
+\{+\} & \text{if}\; n > 0\\
+\{-\} & \text{if}\; n < 0\\
+\{0\} & \text{if}\; n = 0
+\end{cases}$\\
+$[x]_{aenv}$ & $\dn$ & $aenv(x)$\\
+$[e_1 + e_2]_{aenv}$ & $\dn$ & $[e_1]_{aenv} \oplus [e_2]_{aenv}$\\
+$[e_1 * e_2]_{aenv}$ & $\dn$ & $[e_1]_{aenv} \otimes [e_2]_{aenv}$\\
+$[e_1 = e_2]_{aenv}$ & $\dn$ & $\{0, +\}$\\
+\end{tabular}}
+\end{center}
+\scriptsize
+\begin{lstlisting}[language=Scala,numbers=none,xleftmargin=-5mm]
+def aeval_exp(e: Exp, aenv: AEnv) : Set[Abst] = e match {
+case Num(0) => Set(Zero)
+case Num(n) if (n < 0) => Set(Neg)
+case Num(n) if (n > 0) => Set(Pos)
+case Var(x) => aenv(x)
+case Plus(e1, e2) =>
+aplus(aeval_exp(e1, aenv), aeval_exp(e2, aenv))
+case Times(e1, e2) =>
+atimes(aeval_exp(e1, aenv), aeval_exp(e2, aenv))
+case Equ(e1, e2) => Set(Zero, Pos)
+}
+\end{lstlisting}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[fragile]
+\frametitle{AEval for Stmts}
+\mbox{}\\[-12mm]\mbox{}
+Let \bl{$sn$} be the snippets of a program
+\small
+\begin{center}
+\bl{\begin{tabular}{lcl}
+$[\texttt{nil}]_{aenv}$ & $\to$ & $(\texttt{nil},aenv)$\medskip\\
+$[\texttt{Label}(l:)::rest]_{aenv}$ & $\to$ & $(rest, aenv)$\medskip\\
+$[x \,\texttt{:=}\, e::rest]_{aenv}$ & $\to$ &
+$(rest, aenv[x:= [e]_{aenv}])$\medskip\\
+$[\texttt{jmp?}\;e\;l::rest]_{aenv}$ & $\to$ &
+$(sn(l),aenv)$ \textcolor{black}{and} $(rest, aenv)$\medskip\\
+$[\texttt{goto}\;l::rest]_{aenv}$ & $\to$ & $(sn(l), aenv)$\\
+\end{tabular}}
+\end{center}\bigskip
+Start with \bl{$[sn(\mbox{\code{""}})]_{\varnothing}$}, try to
+reach all \emph{states} you can find (until a fix point is reached).
+Check whether there are only $aenv$ in the final states that have
+your property.
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{Sign Analysis}
+\begin{itemize}
+\item We want to find out whether \texttt{a} and \texttt{n}
+are always positive?\medskip
+\item After a few optimisations, we can indeed find this out.
+\begin{itemize}
+\item equal signs return only \texttt{+} or \texttt{0}
+\item branch into only one direction if you know
+\item if $x$ is \texttt{+}, then $x + \texttt{-1}$
+cannot be negative
+\end{itemize}\bigskip
+\item What is this good for? Well, you do not need
+underflow checks (in order to prevent buffer-overflow
+attacks). In general this technique is used to make sure
+keys stay secret.
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{Take Home Points}
+\begin{itemize}
+\item While testing is important, it does not show the
+absence of bugs/vulnerabilities.\medskip
+\item More and more we need (formal) proofs that show
+a program is bug free.\medskip
+\item Static analysis is more and more employed nowadays
+in order to automatically hunt for bugs.
+\end{itemize}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \end{document}
 %%% Local Variables:
 %%% mode: latex
 %%% TeX-master: t
 %%% End:

changeset 538	e03107e79d26
parent 537	55c9f30d0ed2
child 609	ff17a6f694dd