X-Git-Url: https://git.martlubbers.net/?a=blobdiff_plain;f=methods.mtask.tex;h=a0ec96b536f1590926f3f694bd096f00fad86d41;hb=c4c4901bb58dcf6450dd50010e27be66f80b7a00;hp=a35883a596e5944f5afa91da706fdfee1cd007b3;hpb=d118ff9d857683084065145df45135ef6fa06711;p=msc-thesis1617.git diff --git a/methods.mtask.tex b/methods.mtask.tex index a35883a..a0ec96b 100644 --- a/methods.mtask.tex +++ b/methods.mtask.tex @@ -35,22 +35,15 @@ instance isExpr Upd instance isExpr Expr \end{lstlisting} -\section{Semantics} -\gls{mTask} do not behave like functions but more like -\gls{iTasks}-\glspl{Task}. When an \gls{mTask} is created it returns immediatly -and the \gls{Task} will be executed sometime in the future. \glspl{Task} can -run at an interval and they can start other tasks. -\todo{Meer uitwijden over de mTask semantiek} - \section{Expressions} Expressions in the \gls{mTask}-\gls{EDSL} are divided into two types, namely boolean expressions and arithmetic expressions. The class of arithmetic language constructs also contains the function \CI{lit} that lifts a host-language value in to the \gls{EDSL} domain. All standard arithmetic -functions are included but are omitted for brevity. Moreover the class -restrictions are only shown in the first functions and are later omitted. Both -the boolean expression and arithmetic expression classes are shown in -Listing~\ref{lst:arithbool}. +functions are included in the \gls{EDSL} but are omitted in the example for +brevity. Moreover, the class restrictions are only shown in the first functions +and omitted in subsequent funcitons. Both the boolean expression and arithmetic +expression classes are shown in Listing~\ref{lst:arithbool}. \begin{lstlisting}[language=Clean,label={lst:arithbool}, caption={Basic classes for expressions}] @@ -67,12 +60,13 @@ class boolExpr v where \end{lstlisting} \section{Control flow} -Looping of \glspl{Task} happens because \glspl{Task} are launched at regular -intervals or relaunch themselves. Therefore there is no need for loop control -flow functionality such as \CI{While} or \CI{For} constructions. The main -control flow is the sequence operator and the \CI{If} statement. Both are shown -in Listing~\ref{lst:control}. The first class of \CI{If} statements describe -the regular if statement. The expressions given can have any role. The +Looping of \glspl{Task} happens because \glspl{Task} are executed after waiting +a specified amount of time or when they are launched by another task or even +themselves. Therefore there is no need for loop control flow functionality such +as \emph{while} or \emph{for} constructions. The main control flow is the +sequence operator and the \emph{if} statement. Both are shown in +Listing~\ref{lst:control}. The first class of \emph{If} statements describe the +regular \emph{if} statement. The expressions given can have any role. The functional dependency on \CI{s} determines the return type of the statement. The sequence operator is very straightforward and just ties the two expressions together in sequence. @@ -118,7 +112,7 @@ class assign v where \end{lstlisting} A way of storing data in \glspl{mTask} is using \glspl{SDS}. \glspl{SDS} serve -as variables in the \gls{mTask} and will keep their value across executions. +as variables in the \gls{mTask} and maintain their value across executions. The classes associated with \glspl{SDS} are listed in Listing~\ref{lst:sdsclass}. The \CI{Main} class is introduced to box an \gls{mTask} and make it recognizable by the type system. @@ -132,24 +126,79 @@ class sds v where sds :: ((v t Upd)->In t (Main (v c s))) -> (Main (v c s)) | ... \end{lstlisting} +\section{Semantics} +The \gls{C}-backend of the \gls{mTask}-system has an engine that is generated +alongside the code for the \glspl{Task}. This engine will execute the +\glspl{mTask} according to certain rules and semantics. +\glspl{mTask} do not behave like functions but more like +\gls{iTasks}-\glspl{Task}. An \gls{mTask} is queued when either his timer runs +out or when it is started by another \gls{mTask}. When an \gls{mTask} is +queued it does not block the execution but it will return immediately while +the actual \gls{Task} will be executed some time in the future. + +The \gls{iTasks}-backend simulates the \gls{C}-backend and thus uses the same +semantics. This engine expressed in pseudocode is listed as +Algorithm~\ref{lst:engine}. All the \glspl{Task} are inspected on their waiting +time. When the waiting time has not passed the delta is subtracted and they are +pushed to the end of the queue. When the waiting has has surpassed they are +executed. When a \gls{mTask} wants to queue another \gls{mTask} it can just +append it to the queue. + +\begin{algorithm}[H] + \KwData{\textbf{queue} queue, \textbf{time} $t, t_p$} + + $t\leftarrow\text{now}()$\; + \Begin{ + \While{true}{ + $t_p\leftarrow t$\; + $t\leftarrow\text{now}()$\; + \If{notEmpty$($queue$)$}{ + $task\leftarrow \text{queue.pop}()$\; + $task$.wait $\leftarrow task$.wait $-(t-t_p)$\; + \eIf{$task.wait>t_0$}{ + queue.append$(task)$\; + }{ + run\_task$(task)$\; + } + } + } + } + \caption{Engine pseudocode for the \gls{C}- and + \gls{iTasks}-backend}\label{lst:engine} +\end{algorithm} + +To achieve this in the \gls{EDSL} a \gls{Task} clas are added that work in a +similar fashion as the \texttt{sds} class. This class is listed in +Listing~\ref{lst:taskclass}. \glspl{Task} can have an argument and always have +to specify a delay or waiting time. The type signature of the \CI{mtask} is +rather arcane and therefore an example is given. The aforementioned Listing +shows a simple specification containing one task that increments a value +indefinitely every one seconds. + +\begin{lstlisting}[language=Clean,label={lst:taskclass},% + caption={The classes for defining tasks}] +class mtask v a where + task :: (((v delay r) a->v MTask Expr)->In (a->v u p) (Main (v t q))) -> Main (v t q) | ... + +count = task \count = (\n.count (lit 1000) (n +. One)) In {main = count (lit 1000) Zero} +\end{lstlisting} + \section{Example mTask} -\todo{Also explain semantics about running tasks} -Some example \glspl{mTask} using almost all of the functionality are show in +Some example \glspl{mTask} using almost all of the functionality are shown in Listing~\ref{lst:exmtask}. The \glspl{mTask} shown in the example do not belong to a particular view and therefore are of the type \CI{View t r}. The -\CI{blink} \gls{mTask} show the classic \emph{Arduino} \emph{Hello World!} -application that blinks a certain LED every interval. The \CI{thermostat} -\gls{mTask} will enable a digital pin powering a cooling fan when the analog +\CI{blink} \gls{mTask} show the classic \gls{Arduino} \emph{Hello World!} +application that blinks a certain LED every second. The \CI{thermostat} +expression will enable a digital pin powering a cooling fan when the analog pin representing a temperature sensor is too high. \CI{thermostat`} shows the -same program but now using the assignment style \gls{GPIO}. +same expression but now using the assignment style \gls{GPIO} technique. \begin{lstlisting}[% language=Clean,label={lst:exmtask},caption={Some example \glspl{mTask}}] -blink :: Main (View Int Stmt) -blink = sds \x=1 In sds \led=LED1 In {main = - IF (x ==. lit 1) (ledOn led) (ledOff led) :. - x =. lit 1 -. x - } +blink = task \blink=(\x. + IF (x ==. lit True) (ledOn led) (ledOff led) :. + blink (lit 1000) (Not x) + In {main=blink (lit 1000) True} thermostat :: Main (View () Stmt) thermostat = {main =