\input{subfilepreamble}
-\setcounter{chapter}{5}
+\setcounter{chapter}{4}
\begin{document}
\input{subfileprefix}
-\chapter{Implementation}%
+\chapter{The implementation of \texorpdfstring{\gls{MTASK}}{mTask}}%
\label{chp:implementation}
\begin{chapterabstract}
- \noindent This chapter shows the implementation of the \gls{MTASK} system by:
+ This chapter shows the implementation of the \gls{MTASK} system by:
\begin{itemize}
- \item gives details of the implementation of \gls{MTASK}'s \gls{TOP} engine that executes the \gls{MTASK} tasks on the microcontroller;
- \item shows the implementation of the byte code compiler for \gls{MTASK}'s \gls{TOP} language;
- \item explains the machinery used to automatically serialise and deserialise data to-and-fro the device.
+ \item giving details of the implementation of \gls{MTASK}'s \gls{TOP} engine that executes the \gls{MTASK} tasks on the microcontroller;
+ \item showing the implementation of the byte code compiler for \gls{MTASK}'s \gls{TOP} language;
+ \item explaining the machinery used to automatically serialise and deserialise data to-and-fro the device.
\end{itemize}
\end{chapterabstract}
-Microcontrollers usually have flash-based program memory which wears out fairly quick.
-For example, the atmega328p in the \gls{ARDUINO} UNO is rated for 10000 write cycles.
+The \gls{MTASK} language targets resource-constrained edge devices that have little memory, processor speed and communication.
+Furthermore, microcontrollers usually have flash-based program memory which wears out fairly quick.
+For example, the flash memory of the popular atmega328p powering the \gls{ARDUINO} UNO is just rated for 10000 write cycles.
While this sounds like a lot, if new tasks are sent to the device every minute or so, a lifetime of only seven days is guaranteed.
-Hence, for dynamic applications, interpretation on the device is necessary, saving precious write cycles of the program memory.
+Hence, for dynamic applications, storing the program in the \gls{RAM} of the device and interpreting this code is necessary, saving precious write cycles of the program memory.
-In order to provide the device with the tools to interpret the byte code, it is programmed with a \gls{RTS}, a customisable domain-specific \gls{OS} that takes care of the execution of tasks but also low-level mechanisms such as the communication, multi tasking, and memory management.
-Once the device is programmed with the \gls{MTASK} \gls{RTS}, it can continuously receive new tasks without the need for reprogramming.
+In the \gls{MTASK} system, this is done by the \gls{MTASK} \gls{RTS}.
+The \gls{RTS} is a customisable domain-specific \gls{OS} that takes care of the execution of tasks, but also low-level mechanisms such as the communication, multitasking, and memory management.
+Once a device is programmed with the \gls{MTASK} \gls{RTS}, it can continuously receive new tasks without the need for reprogramming.
The \gls{OS} is written in portable \ccpp{} and only contains a small device-specific portion.
+In order to keep the abstraction level high and the hardware requirements low, much of the high-level functionality of the \gls{MTASK} language is implemented not in terms of lower-level constructs from \gls{MTASK} language but in terms of \ccpp{} code.
\section{\texorpdfstring{\Glsxtrlong{RTS}}{Run time system}}
The event loop of the \gls{RTS} is executed repeatedly and consists of three distinct phases.
The interface is deliberately kept simple and consists of a two layer interface: a link interface and a communication interface.
Besides opening, closing and cleaning up, the link interface has only three functions that are shown in \cref{lst:link_interface}.
Consequently, implementing this link interface is very simple but allows for many more advanced link settings such as buffering.
-There are implementations for this interface for serial or Wi-Fi connections using \gls{ARDUINO} and \gls{TCP} connections for Linux.
+There are implementations for this interface for serial or \gls{WIFI} connections using \gls{ARDUINO} and \gls{TCP} connections for Linux.
\begin{lstArduino}[caption={Link interface of the \gls{MTASK} \gls{RTS}.},label={lst:link_interface}]
bool link_input_available(void);
\section{Compiler}
\subsection{Instruction set}
-The instruction set is a fairly standard stack machine instruction set extended with special \gls{TOP} instructions.
+The instruction set is a fairly standard stack machine instruction set extended with special \gls{TOP} instructions for creating task tree nodes.
+All instructions are housed in a \gls{CLEAN} \gls{ADT} and serialised to the byte representation using a generic function.
+Type synonyms (\cref{lst:type_synonyms}) are used to provide insight on the arguments of the instructions.
+Labels are always two bytes long, all other arguments are one byte long.
-\Cref{lst:instruction_type} shows the \gls{CLEAN} type representing the instruction set of which \cref{tbl:instr_task} gives detailed semantics.
-Type synonyms are used to provide insight on the arguments of the instructions.
-One notable instruction is the \cleaninline{MkTask} instruction, it allocates and initialises a task tree node and pushes a pointer to it on the stack.
-
-\begin{lstClean}[caption={The type housing the instruction set.},label={lst:instruction_type}]
+\begin{lstClean}[caption={Type synonyms for instructions arguments.},label={lst:type_synonyms}]
:: ArgWidth :== UInt8 :: ReturnWidth :== UInt8
:: Depth :== UInt8 :: Num :== UInt8
:: SdsId :== UInt8 :: JumpLabel =: JL UInt16
+\end{lstClean}
-//** Datatype housing all instructions
+\Cref{lst:instruction_type} shows an excerpt of the \gls{CLEAN} type that represents the instruction set.
+For example, shorthand instructions are omitted for brevity.
+Detailed semantics for the instructions are given in \cref{chp:bytecode_instruction_set}.
+One notable instruction is the \cleaninline{MkTask} instruction, it allocates and initialises a task tree node and pushes a pointer to it on the stack.
+
+\begin{lstClean}[caption={The type housing the instruction set.},label={lst:instruction_type}]
:: BCInstr
- //Return instructions
//Jumps
= BCJumpF JumpLabel | BCJump JumpLabel | BCLabel JumpLabel | BCJumpSR ArgWidth JumpLabel
| BCReturn ReturnWidth ArgWidth | BCTailcall ArgWidth ArgWidth JumpLabel
| BCArgs ArgWidth ArgWidth
//Task node creation and refinement
| BCMkTask BCTaskType | BCTuneRateMs | BCTuneRateSec
- //Task value ops
- | BCIsStable | BCIsUnstable | BCIsNoValue | BCIsValue
//Stack ops
| BCPush String255 | BCPop Num | BCRot Depth Num | BCDup | BCPushPtrs
//Casting
| BCAddI | BCSubI | ...
...
-//** Datatype housing all task types
:: BCTaskType
- = BCStableNode ArgWidth | ArgWidth
+ = BCStableNode ArgWidth | BCUnstableNode ArgWidth
// Pin io
| BCReadD | BCWriteD | BCReadA | BCWriteA | BCPinMode
// Interrupts
// Repeat
| BCRepeat
// Delay
- | BCDelay | BCDelayUntil //* Only for internal use
+ | BCDelay | BCDelayUntil
// Parallel
| BCTAnd | BCTOr
//Step
...
\end{lstClean}
-\subsection{Compiler}
+\subsection{Compiler infrastructure}
The bytecode compiler interpretation for the \gls{MTASK} language is implemented as a monad stack containing a writer monad and a state monad.
The writer monad is used to generate code snippets locally without having to store them in the monadic values.
The state monad accumulates the code, and stores the stateful data the compiler requires.
\Cref{lst:compiler_state} shows the data type for the state, storing:
function the compiler currently is in;
code of the main expression;
-context (see \todo{insert ref to compilation rules step here});
+context (see \cref{ssec:step});
code for the functions;
next fresh label;
a list of all the used \glspl{SDS}, either local \glspl{SDS} containing the initial value (\cleaninline{Left}) or lifted \glspl{SDS} (see \cref{sec:liftsds}) containing a reference to the associated \gls{ITASK} \gls{SDS};
and finally there is a list of peripherals used.
-\begin{lstClean}[label={lst:compiler_state},caption={\Gls{MTASK}'s byte code compiler type}]
+\begin{lstClean}[label={lst:compiler_state},caption={The type for the \gls{MTASK} byte code compiler}]
:: BCInterpret a :== StateT BCState (WriterT [BCInstr] Identity) a
:: BCState =
{ bcs_infun :: JumpLabel
Furthermore, redundant instructions (e.g.\ pop directly after push) are removed as well in order not to burden the code generation with these intricacies.
Finally the labels are resolved to represent actual program addresses instead of freshly generated identifiers.
After the byte code is ready, the lifted \glspl{SDS} are resolved to provide an initial value for them.
-The result---byte code, \gls{SDS} specification and perpipheral specifications---are the result of the process, ready to be sent to the device.
+The result---byte code, \gls{SDS} specification and perpipheral specifications---are the result of the process, ready to be sent to the device.
\section{Compilation rules}
This section describes the compilation rules, the translation from abstract syntax to byte code.
rtrn m = m >>| tell` [BCMkTask (bcstable m)]
\end{lstClean}
-\subsection{Step combinator}\label{ssec:step}
+\todo[inline]{uitleg delay}
+
+\subsection{Sequential combinator}\label{ssec:step}
The \cleaninline{step} construct is a special type of task because the task value of the left-hand side may change over time.
Therefore, the continuation tasks on the right-hand side are \emph{observing} this task value and acting upon it.
In the compilation scheme, all continuations are first converted to a single function that has two arguments: the stability of the task and its value.
Compiling \cleaninline{getSds} is a matter of executing the \cleaninline{BCInterpret} representing the \gls{SDS}, which yields the identifier that can be embedded in the instruction.
Setting the \gls{SDS} is similar: the identifier is retrieved and the value is written to put in a task tree so that the resulting task can remember the value it has written.
-Lifted SDSs are compiled in a very similar way.\todo{deze \P{} moet naar integration?}
-The only difference is that there is no initial value but an iTasks SDS when executing the Clean function.
-A lens on this SDS converting \cleaninline{a} from the \cleaninline{Shared a} to a \cleaninline{String255}---a bytecode encoded version---is stored in the state.
-The encoding and decoding itself is unsafe when used directly but the type system of the language and the abstractions make it safe.
-Upon sending the mTask task to the device, the initial values of the lifted SDSs are fetched to complete the SDS specification.
+Lifted SDSs are compiled in a very similar way \cref{sec:liftsds}.
% VimTeX: SynIgnore on
\begin{lstClean}[caption={Backend implementation for the SDS classes.},label={lst:comp_sds}]
\end{lstClean}
% VimTeX: SynIgnore off
-\section{C code generation}\label{sec:ccodegen}
+\section{\texorpdfstring{\Gls{C}}{C} code generation}\label{sec:ccodegen}
All communication between the \gls{ITASK} server and the \gls{MTASK} server is type-parametrised.
From the structural representation of the type, a \gls{CLEAN} parser and printer is constructed using generic programming.
Furthermore, a \ccpp{} parser and printer is generated for use on the \gls{MTASK} device.
The technique for generating the \ccpp{} parser and printer is very similar to template metaprogramming and requires a generic programming library or compiler support that includes a lot of metadata in the record and constructor nodes.
\section{Conclusion}
-%\todo[inline]{conclusion}
+Tasks in the \gls{MTASK} system are executed on resource-constrained \gls{IOT} edge devices.
+
+\todo[inline]{conclusion}
\input{subfilepostamble}
\end{document}
repositories / phd-thesis.git / blobdiff