X-Git-Url: https://git.martlubbers.net/?a=blobdiff_plain;f=results.mtask.tex;h=c6adefb744f7d71e9b2dd47c6591be82751bc3b3;hb=36d2564cca6ffab6506198f13545e5d02cf2b5cc;hp=1872019b9d20e007864d68481213f27f88427ec5;hpb=4a3a621122fc747cdf156468efd3c06f896f70dc;p=msc-thesis1617.git diff --git a/results.mtask.tex b/results.mtask.tex index 1872019..c6adefb 100644 --- a/results.mtask.tex +++ b/results.mtask.tex @@ -1,11 +1,11 @@ -The \glspl{Task} suitable for a client are called \glspl{mTask} and are written -in the aforementioned \gls{mTask}-\gls{EDSL}. Some functionality of the -original \gls{mTask}-\gls{EDSL} will not be used in this system. Conversely, -some functionality needed was not available in the existing \gls{EDSL}. Due to -the nature of class based shallow embedding this obstacle is easy to -solve. A type --- housing the \gls{EDSL} --- does not have to implement all the -available classes. Moreover, classes can be added at will without interfering -with the existing views. +The \glspl{Task} suitable for a client are called \gls{mTask}-\gls{Task} and +are written in the aforementioned \gls{mTask}-\gls{EDSL}. Some functionality of +the original \gls{mTask}-\gls{EDSL} will not be used in this system. +Conversely, some functionality needed was not available in the existing +\gls{EDSL}. Due to the nature of class based shallow embedding this obstacle is +easy to solve. A type --- housing the \gls{EDSL} --- does not have to implement +all the available classes. Moreover, classes can be added at will without +interfering with the existing views. \section{\gls{Task} Semantics} The current \gls{mTask} engine for devices does not support \glspl{Task} in the @@ -31,24 +31,25 @@ reflected in the \CI{MTTask} message type. \item\CI{OnInterrupt} The last scheduling method is running \glspl{Task} on a specific - interrupt. None of the current client implementations support this. - However, registering interrupts on, for example the \gls{Arduino} is - very straightforward. Interrupt scheduling is useful for \glspl{Task} - that have to react on a certain type of hardware event such as the - press of a button. + interrupt. Unfortunatly, due to time constraints and focus, none of the + current client implementations support this. Interrupt scheduling is + useful for \glspl{Task} that have to react on a certain type of + hardware event such as the press of a button. \end{itemize} \section{\gls{SDS} semantics} \Glspl{SDS} on a client are available on the server as well as regular -\gls{SDS}. However, the same freedom is not given on the \glspl{SDS} that -reside on the client. Not all types are suitable to be located on a client. -Moreover, \glspl{SDS} behave a little different on an \gls{mTask} device -compared to the \gls{iTasks} system. In an \gls{iTasks} system, when the +\glspl{SDS}. However, the same freedom is not given for \glspl{SDS} that +reside on the client. Not all types are suitable to be located on a client, +simply because it needs to be serializable and representable on clients. +Moreover, \glspl{SDS} behave a little different in an \gls{mTask} device +compared to in the \gls{iTasks} system. In an \gls{iTasks} system, when the \gls{SDS} is updated, a broadcast to all watching \glspl{Task} in the system is made to notify them of the update. \glspl{SDS} can update often and the -update might not be the final value it will get. This results in a lot of -expensive unneeded bandwidth usage. Therefore a device must publish the -\gls{SDS} explicitly to save bandwidth. +update might not be the final value it will get. Implementing the same +functionality on the \gls{mTask} client would result in a lot of expensive +unneeded bandwidth usage. Therefore a device must publish the \gls{SDS} +explicitly to save bandwidth. To add this functionality, the \CI{sds} class could be extended. However, this would result in having to update all existing views that use the \CI{sds} @@ -62,9 +63,9 @@ class sdspub v where \end{lstlisting} \section{Bytecode compilation view}\label{sec:compiler} -The \glspl{mTask} are sent to the device in bytecode and are saved in the -memory of the device. To compile the \gls{EDSL} code to bytecode, a view is -added to the \gls{mTask}-system encapsulated in the type \CI{ByteCode}. As +The \gls{mTask}-\glspl{Task} are sent to the device in bytecode and are saved +in the memory of the device. To compile the \gls{EDSL} code to bytecode, a view +is added to the \gls{mTask}-system encapsulated in the type \CI{ByteCode}. As shown in Listing~\ref{lst:bcview}, the \CI{ByteCode} view is a boxed \gls{RWST} that writes bytecode instructions (\CI{BC}, Subsection~\ref{sec:instruction}) while carrying around a \CI{BCState}. The state is kept between compilations @@ -117,8 +118,8 @@ instance serial ByteCode \subsection{Instruction Set}\label{sec:instruction} The instruction set is given in Listing~\ref{bc:instr}. The instruction set is -kept large, but under $255$, to get the highest expressivity while keeping all -instruction within one byte. +kept large, but under $255$, to get as much expressieve power as possible while +keeping all instruction within one byte. The interpreter running in the client is a stack machine. The virtual instruction \CI{BCLab} is added to allow for an easy implementation of jumping. @@ -152,20 +153,21 @@ and avoid label lookups at runtime. | BCReturn \end{lstlisting} -All single byte instructions are converted automatically using the generic -function \CI{consIndex} which returns the index of the constructor. The index -of the constructor is the byte value for all instructions. The last step of the +All single byte instructions are converted automatically using a generic +function which returns the index of the constructor. The index of the +constructor is the byte value for all instructions. Added to this single byte +value are the encoded parameters of the instruction. The last step of the compilation is transforming the list of bytecode instructions to actual bytes. \subsection{Helper functions} -The \CI{ByteCode} type is just a boxed \gls{RWST} and that gives access to -the whole range of \gls{RWST} functions. However, to apply a function the type -must be unboxed. After application the type must be boxed again. To achieve -this, several helper functions have been created. They are listed in +Since the \CI{ByteCode} type is just a boxed \gls{RWST}, access to the whole +range of \gls{RWST} functions is available. However, to use this, the type must +be unboxed. After application the type must be boxed again. To achieve this, +several helper functions have been created. They are given in Listing~\ref{lst:helpers}. The \CI{op} and \CI{op2} functions is hand-crafted to make operators that pop one or two values off the stack respectively. The -\CI{tell`} is a wrapper around the \gls{RWST} function \CI{tell} that appends -the argument to the \emph{Writer} value. +\CI{tell`} function is a wrapper around the \gls{RWST} function \CI{tell} that +appends the argument to the \emph{Writer} value. \begin{lstlisting}[label={lst:helpers},caption={Some helper functions}] op2 :: (ByteCode a p1) (ByteCode a p2) BC -> ByteCode b Expr @@ -183,9 +185,9 @@ unBC (BC x) = x \subsection{Arithmetics \& Peripherals} Almost all of the code from the simple classes exclusively use helper -functions. Listing~\ref{lst:arithview} shows some implementations. The classes -\CI{boolExpr} and the classes for the peripherals are implemented using the -same strategy. +functions. Listing~\ref{lst:arithview} shows some implementations. The +\CI{boolExpr} class and the classes for the peripherals are implemented using +the same strategy. \begin{lstlisting}[label={lst:arithview},caption={% Bytecode view implementation for arithmetic and peripheral classes}] @@ -201,13 +203,12 @@ instance userLed ByteCode where \subsection{Control Flow} Implementing the sequence operator is very straightforward in the bytecode -view. The function just sequences the two \glspl{RWST}. The \emph{If} statement -requires some detailed explanation since labels come into play. The -implementation speaks for itself in Listing~\ref{lst:controlflow}. First, all -the labels are gathered after which they are placed in the correct order in the -bytecode sequence. It can happen that multiple labels appear consecutively in -the code. This is not a problem since the labels are resolved to real addresses -later on anyway. +view. The function just sequences the two \glspl{RWST}. The +implementation for the \emph{If} statement speaks for itself in +Listing~\ref{lst:controlflow}. First, all the labels are gathered after which +they are placed in the correct order in the bytecode sequence. It can happen +that multiple labels appear consecutively in the code. This is not a problem +since the labels are resolved to real addresses later on anyway. \begin{lstlisting}[label={lst:controlflow},% caption={Bytecode view for \texttt{arith} class}] @@ -231,13 +232,13 @@ instance noOp ByteCode where noOp = tell` [BCNop] \end{lstlisting} -The semantics for the \glspl{mTask} bytecode view are different from the -semantics for the \gls{C} view. \glspl{Task} in the \gls{C} view can start new -\gls{Task} or themselves to continue, while in the bytecode view, \gls{Task} -run idefinitly, one-shot or on interrupt. To allow interval and interrupt -\glspl{Task} to terminate, a return instruction is added. This class was not -available in the original system and is thus added. It just writes a single -instruction so that the interpreter knows to stop execution. +The semantics for the \gls{mTask}-\glspl{Task} bytecode view are different from +the semantics of the \gls{C} view. \glspl{Task} in the \gls{C} view can start +new \glspl{Task} or even start themselves to continue, while in the bytecode +view, \glspl{Task} run indefinitly, one-shot or on interrupt. To allow interval +and interrupt \glspl{Task} to terminate, a return instruction is added. This +class was not available in the original system and is thus added. It just +writes a single instruction so that the interpreter knows to stop execution. Listing~\ref{lst:return} shows the classes and implementation for the return expression. @@ -275,14 +276,14 @@ instance sdspub ByteCode where addSDS sds v s = {s & sdss=[{sds & sdsval=BCValue v}:s.sdss]} \end{lstlisting} -All assignable types compile to a \gls{RWST} that writes one fetch instruction. -For example, using a \gls{SDS} always results in an expression of the form -\CI{sds \x=4 In ...}. The actual \CI{x} is the \gls{RWST} that always writes -one \CI{BCSdsFetch} instruction with the correctly embedded \gls{SDS}. -Assigning to an analog pin will result in the \gls{RWST} containing the -\CI{BCAnalogRead} instruction. When the operation on the assignable is not a -read operation from but an assign operation, the instruction(s) will be -rewritten accordingly. This results in an \CI{BCSdsStore} or \CI{BCAnalogWrite} +All assignable types compile to a \gls{RWST} which writes the specific fetch +instruction(s). For example, using an \gls{SDS} always results in an expression +of the form \CI{sds \x=4 In ...}. The actual \CI{x} is the \gls{RWST} that +always writes one \CI{BCSdsFetch} instruction with the correctly embedded +\gls{SDS}. Assigning to an analog pin will result in the \gls{RWST} containing +the \CI{BCAnalogRead} instruction. When the operation on the assignable is not +a read operation from but an assign operation, the instruction(s) will be +rewritten accordingly. This results in a \CI{BCSdsStore} or \CI{BCAnalogWrite} instruction respectively. The implementation for this is given in Listing~\ref{lst:assignmentview}. @@ -298,15 +299,15 @@ makeStore [...] = [...] \subsection{Actual Compilation} All the previous functions are tied together with the \CI{toMessages} function. -This function compiles the bytecode and transforms the \gls{Task} in a message. +This function compiles the bytecode and transforms the \gls{Task} to a message. The \glspl{SDS} that were not already sent to the device are also added as -messages to be sent to the device. This functionality is listed in +messages to be sent to the device. This functionality is shown in Listing~\ref{lst:compilation}. The compilation process consists of two steps. First, the \gls{RWST} is executed. Then, the \emph{Jump} statements that jump to labels are transformed to jump to program memory addresses. The -translation of labels is possible in one sweep because no labels are reused. +translation of labels is possible in one sweep because fresh labels are reused. Reusing labels would not give a speed improvement since the labels are removed -anyway in the end. +in the end. \begin{lstlisting}[label={lst:compilation},% caption={Actual compilation.}] @@ -334,7 +335,7 @@ toMessages interval x oldstate \end{lstlisting} \section{Examples} -The heating example given previously in Listing~\ref{lst:exmtask} would be +The thermostat example given previously in Listing~\ref{lst:exmtask} would be compiled to the following code. The left column indicates the position in the program memory.