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Jonatan Pålsson 2011-05-12 23:23:47 +02:00
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@ -3523,7 +3523,7 @@ As mentioned earlier in the thesis, a prototype of the GGS has been developed
\end_layout
\begin_layout Standard
This chapter contains the realization of much of the principles and techniques
This chapter contains the realization of many of the principles and techniques
described in chapter
\begin_inset CommandInset ref
LatexCommand vref
@ -3539,11 +3539,6 @@ reference "cha:Theory"
\begin_layout Standard
Much of what is discussed in this chapter has been implemented in the GGS
prototype.
Specific solutions such as
\emph on
supervisor structures
\emph default
and distribution of erlang nodes on physical nodes.
The different means of communications within the GGS and outside the GGS
with third parties are also discussed here.
\end_layout
@ -3578,11 +3573,11 @@ Light Weight Processes; LWP
\emph default
much like the threads in an operating system.
There are however differences between operating system threads and the
LWPs of erlang.
LWPs in Erlang.
Threads in a Linux system, for example, are treated much like operating
system processes in different systems.
Due to the size of data structures related to each process, swapping one
process for another (known as
Due to the size of the data structures related to each process swapping
one process for another (known as
\emph on
context switching
\emph default
@ -3626,8 +3621,9 @@ textbf{Context switch}}{The act of switching from one context, commonly
\begin_layout Standard
The cost of swapping operating system processes becomes a problem when many
processes are involved.
If the GGS system had been developed using regular operating system processes,
it would have had to be designed in a way to minimize the number of processes.
If the GGS prototype had been developed using regular operating system
processes, it would have had to be designed in a way to minimize the number
of processes.
Using Erlang, which is capable of running very many processes, several
times more than an operating system, the relation between the real world
and the GGS (described in
@ -3654,9 +3650,9 @@ In addition to creating (or
\emph on
spawning
\emph default
) processes specifically to handle new players connecting, the GGS has more
permanent processes running at all times.
The constantly running processes in the GGS system are called
) processes specifically to handle new players connecting, the GGS has permanent
processes running at all times.
The constantly running processes in the GGS prototype are called
\emph on
modules
\emph default
@ -3758,7 +3754,7 @@ reference "fig:The-layout-of"
\end_inset
the entire GGS system is represented graphically.
The circles marked with 'C' topmost in the picture represents game clients.
The circles marked with 'C' topmost in the picture represent game clients.
These circles represent processes running on gamers computers, and not
on the GGS machine.
If a game of chess is to be played on the server, the clients on the machines
@ -3848,16 +3844,15 @@ In Erlang, everything is a process, and everything operates in its own memory
\begin_layout Standard
Messages are sent between the processes in an asynchronous manner, and each
process has a mailbox in which these messages can be retrieved.
process has a mailbox from which these messages can be retrieved.
\end_layout
\begin_layout Standard
Processes in Erlang are also called
\emph on
Light Weight Processes.
Light Weight Processes
\emph default
The Erlang processes are inexpensive to create.
because they are inexpensive to create.
Processes exist within an Erlang machine, or Erlang node.
The Erlang machine has its own scheduler and does not rely on the scheduler
of the operating system, this is a main reason of Erlang's capability of
@ -3872,7 +3867,7 @@ key "Armstrong03"
\end_layout
\begin_layout Standard
The strong isolation of Erlang processes make them ideal for multi-core
The strong isolation of Erlang processes makes them ideal for multi-core
and distributed systems.
Distribution of software is included as a fundamental part in the Erlang
language.
@ -3884,12 +3879,12 @@ The strong isolation of Erlang processes make them ideal for multi-core
\end_layout
\begin_layout Standard
The distributed nature of Erlang is something the GGS can make use of, when
The distributed nature of Erlang is something the GGS can make use of when
scaling across several computers in order to achieve higher performance.
The distribution is also important in creating redundancy.
The GGS prototype does not make use of the distributed nature of Erlang,
however the GGS prototype is constructed in such a way that making use
of the distributed nature should now pose a big ptoblem.
of the distributed nature should not pose a big problem.
\end_layout
\begin_layout Standard
@ -3956,7 +3951,7 @@ reference "sub:UUID"
\end_inset
and NIFs for interfacing with the virtual machines of games
and NIFs for interfacing with the GDL VMs
\begin_inset Foot
status collapsed
@ -4047,7 +4042,7 @@ The
\emph on
gen_tcp
\emph default
behavior, which is used to work with TCP sockets for network communication.
behavior, which is used to interact with TCP sockets for network communication.
Using the gen_tcp behavior, network messages are converted to internal
Erlang messages and passed to a protocol parser, where the messages are
processed further.
@ -4061,8 +4056,7 @@ gen_server
behavior, which is used when constructing OTP servers in Erlang.
Using this behavior, a state can easily be kept in a server process, greatly
increasing the usefulness of the server process.
There are many gen_servers in the GGS, it is the most widely used behavior
in the project.
This behaviour is the most widely used one in the GGS prototype.
In addition to introducing a state to the server, the gen_server behavior
also imposes patterns for synchronous and asynchronous communication between
other gen_servers and other OTP behaviors.
@ -4086,7 +4080,7 @@ In addition to supplying behaviors, the OTP also has a style for packaging
\emph on
application
\emph default
the GGS can be started in a way uniform to most erlang software, providing
the GGS can be started in a way uniform to most Erlang software, providing
familiarity for other Erlang users, and eases the incorporation of the
GGS in other applications.
\begin_inset ERT
@ -4297,7 +4291,7 @@ tt "Hello world"}
\series bold
Records
\series default
are erlang tuples coupled with a tag for each tuple element.
are Erlang tuples coupled with a tag for each tuple element.
This allows referring to elements by name instead of by position.
An example of a record looks like this:
\begin_inset ERT
@ -5809,7 +5803,7 @@ TODO: Go in to more detail about how the world, player and localstorage
status open
\begin_layout Plain Layout
My idea here is that we describe the erlang-js (which failed, but nontheless),
My idea here is that we describe the Erlang-js (which failed, but nontheless),
v8, UUID and other external communication.
We shouldn't describe sockets here though..
or..
@ -6144,14 +6138,13 @@ Redundancy
\end_layout
\begin_layout Standard
The modules in the GGS are built to be capable of redundant operation.
The modules in the GGS are built to be capable of redundant operations.
By adding a backup process to sensitive processes, the state can be kept
in the event of a crash.
The coordinator of the GGS prototype has this backup feature built in.
The coordinator passes state along to the backup process which keeps the
data safe.
In the event of a crash, the coordinator recovers the state from the backup
process.
If a crash occurs, the coordinator recovers the state from the backup process.
Figure
\begin_inset CommandInset ref
LatexCommand ref
@ -6268,11 +6261,11 @@ Testing
\end_layout
\begin_layout Standard
In order to make sure the GGS prototype adheres to the specification set,
two different approaches to software testing are used.
To make sure the GGS prototype adheres to the specification set, two different
approaches to software testing are used.
For simpler testing the GGS prototype uses unit tests.
Modules are tested on a high level, making sure each function in the module
tested functions according to specification.
tested functions has been tested according to specification.
\end_layout
\begin_layout Standard
@ -6299,14 +6292,14 @@ Unit testing
\begin_layout Standard
Unit testing is a way to check if the functionality adheres to the specification
of the system by manually creating test cases for sections of code.
In most cases whole functions.
Usually whole functions.
Unit testing is good, not only for revealing software bugs, but also to
state that a feature is working according to the specification.
\end_layout
\begin_layout Standard
Unit testing is a useful way to create regression tests.
Unit testing is an useful way to create regression tests.
Regression tests are used to make sure changes made to the GGS do not introduce
new bugs or break the specification.
The regression tests are optimally run very often, such as after each change
@ -6316,7 +6309,7 @@ Unit testing is a useful way to create regression tests.
\begin_layout Standard
Erlang provides a module for unit testing called eunit.
Eunit, being a part of OTP, is rich in functionality and well documented,
it doesn't however allow any means of testing asynchronous behaviours as
it does not however allow any means of testing asynchronous behaviors as
opposed to other means of software testing.
\end_layout
@ -6327,8 +6320,8 @@ Automated test case generation
\begin_layout Standard
The problem of writing software tests manually is that it takes a lot of
time.
There exists other ways to test software that address this problem by generatin
g test cases with certain properties.
There exists other ways to test software that addresses this problem by
generating test cases with certain properties.
This allows for testing functions with a lot of different input parameters
without having to implement each specific test itself.
@ -6341,8 +6334,8 @@ By having each test automatically generated, each test can be very complex
By using QuickCheck the GGS can be tested with input which would be extremely
difficult to construct using manual testing methods.
Regression tests, such as the unit tests used by the GGS are more useful
for ensuring the system does not diverge from a working scenario than for
finding new cases where the specification does not hold
for ensuring that the system does not diverge from a working scenario than
for finding new cases where the specification does not hold
\begin_inset CommandInset citation
LatexCommand citet
key "Arts:2006:TTS:1159789.1159792"
@ -6366,7 +6359,7 @@ QuickCheck has features to generate very large and complex tests, the results
\emph on
minimal failing test case
\emph default
which contains the smalles failing test sequence.
which contains the smallest failing test sequence.
By applying a very large test and gradually simplifying the test to find
the smallest failing sequence, many bugs which would other wise have been
hard to catch can be caught
@ -6381,7 +6374,7 @@ key "Arts:2006:TTS:1159789.1159792"
\begin_layout Standard
QuickCheck was originally made for the programming language Haskell.
There are a lot of reimplementations of QuickCheck in various programming
There is a lot of reimplementations of QuickCheck in various programming
languages.
Erlang QuickCheck (EQC) and Triq are two variants of QuickCheck for Erlang.
EQC was chosen for testing the GGS.
@ -7355,7 +7348,7 @@ There are two JavaScript virtual machines, or
\emph on
engines,
\emph default
with suitable bindings to erlang available at the time of the writing of
with suitable bindings to Erlang available at the time of the writing of
this thesis.
There is a group of machines developed by Mozilla called
\emph on