simulate a three-state process model (ready, running and blocked)

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CSci 430 Spring 2019

Objectives:

ˆ Explore the Process state models from an implementation point of

view.

ˆ Practice using basic queue data types and implementing in C.

ˆ Use C/C++ data structures to implement a process control block and

round robin scheduling queues.

ˆ Learn about Process switching and multiprogramming concepts.

Description:

In this assignment you will simulate a Three-State process model (ready,

running and blocked) and a simple process control block structure as dis-

cussed in Chapter 3. Your program will read input and directives from a

le. The input describes a time sequence of events that occur. These are the

full set of events you will simulate:

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Event Description

cpu The processor executes for 1 time step the currently running process

new A new process is created and put at tail of the ready queue

done The currently running process has nished

wait X The currently running process has done an I/O operation and

is waiting on event X

event X Event X has occurred, the process waiting on that event should

be made ready.

The input le will simply be a list of events that occur in the system, in

the order they are to occur. For example:

—– simulation-01.sim ——–

new

cpu

cpu

cpu

new

cpu

cpu

cpu

cpu

wait 1

cpu

cpu

event 1

cpu

cpu

done

cpu

cpu

cpu

cpu

exit

———————————-

Your task is to read in the events, and simulate the creation and execution

of processes in the system as they move through the various three-states of

their process life cycle. You need to:

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ˆ Dene a simple process control block (PCB) to hold information about

all processes currently running in your system. The PCB can be a

simple C struct or a C++ class. At a minimum you need to have a

eld for the process identier and the process state (Ready, Running or

Blocked). You need to also keep track of the time step that the process

entered the system, and the number of steps the process has been

running. Minimal credit will be given to programs that at least handle

new events and create a process in a simulated PCB. You probably

need a list or an array to hold the current processes that have been

created and are being managed by your simulated system.

ˆ You will need a ready queue of some kind. You should use a C++

Standard Template Library (STL) container to manage your ready

queue.

ˆ You will need to implement a simple dispatcher function. Whenever

a cpu event occurs, and no process is currently running, you should

select the next Ready process from the head of your ready queue and

start it running on the processor.

ˆ You need to also implement a simple time slicing mechanism. The

time slice value to use will be passed into your program when it is

started. At the end of a cpu cycle, you should check if the currently

running process has executed for its full time quantum. In that case,

the currently running process should timeout, and be returned to the

end of the Ready queue.

ˆ new events should cause a new process to be created (including creating

its PCB and lling it in). New processes should be placed on the tail

of the ready queue after being created. You should assign each new

process a process identier. The process identier should be a simple

integer value, and you should start numbering processes from 1.

ˆ For a done event, if a process is currently running it should then be

released. It should be removed from the CPU, and not placed back on

the ready or blocked queue. If a done occurs when the CPU is idle,

then nothing will happen as a result of this event.

ˆ A wait event simulates the currently running process performing some

I/O operation. If a wait occurs, the currently running process should

become blocked and put on the blocked queue. You also need an entry

in the PCB so you know what event the process is waiting for. The

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wait event is followed by an integer number, which is an indication of

the type of event the process has requested.

ˆ Likewise the event directive simulates the nishing of some I/O oper-

ation. When an event occurs, you should scan your blocked processes

and make any process ready that was waiting on that event. The in-

teger value following an event indicates the type of event that just

occurred.

You have been given some example event sequences (simulation-01.sim,

simulation-02.sim, etc.) along with the expected output for those sequence

of events (simulation-01.res, simulation-02.res, etc.). The output of your

program should be sent to standard output. The correct output for the

simulation-01.sim simulation is:

Time: 1

CPU (currently running):

pid=1, state=RUNNING, start=1, slice=1,

Ready Queue:

EMPTY

Blocked Queue:

EMPTY

Time: 2

CPU (currently running):

pid=1, state=RUNNING, start=1, slice=2,

Ready Queue:

EMPTY

Blocked Queue:

EMPTY

Time: 3

CPU (currently running):

pid=1, state=RUNNING, start=1, slice=3,

Ready Queue:

EMPTY

Blocked Queue:

EMPTY

Time: 4

CPU (currently running):

4

pid=1, state=RUNNING, start=1, slice=4,

Ready Queue:

pid=2, state=READY, start=4, slice=0,

Blocked Queue:

EMPTY

Time: 5

CPU (currently running):

pid=1, state=RUNNING, start=1, slice=5,

Ready Queue:

pid=2, state=READY, start=4, slice=0,

Blocked Queue:

EMPTY

Time: 6

CPU (currently running):

pid=2, state=RUNNING, start=4, slice=1,

Ready Queue:

pid=1, state=READY, start=1, slice=5,

Blocked Queue:

EMPTY

Time: 7

CPU (currently running):

pid=2, state=RUNNING, start=4, slice=2,

Ready Queue:

pid=1, state=READY, start=1, slice=5,

Blocked Queue:

EMPTY

Time: 8

CPU (currently running):

pid=1, state=RUNNING, start=1, slice=1,

Ready Queue:

EMPTY

Blocked Queue:

pid=2, state=BLOCKED, start=4, slice=2, event=1

Time: 9

CPU (currently running):

5

pid=1, state=RUNNING, start=1, slice=2,

Ready Queue:

EMPTY

Blocked Queue:

pid=2, state=BLOCKED, start=4, slice=2, event=1

Time: 10

CPU (currently running):

pid=1, state=RUNNING, start=1, slice=3,

Ready Queue:

pid=2, state=READY, start=4, slice=2,

Blocked Queue:

EMPTY

Time: 11

CPU (currently running):

pid=1, state=RUNNING, start=1, slice=4,

Ready Queue:

pid=2, state=READY, start=4, slice=2,

Blocked Queue:

EMPTY

Time: 12

CPU (currently running):

pid=2, state=RUNNING, start=4, slice=1,

Ready Queue:

EMPTY

Blocked Queue:

EMPTY

Time: 13

CPU (currently running):

pid=2, state=RUNNING, start=4, slice=2,

Ready Queue:

EMPTY

Blocked Queue:

EMPTY

Time: 14

CPU (currently running):

6

pid=2, state=RUNNING, start=4, slice=3,

Ready Queue:

EMPTY

Blocked Queue:

EMPTY

Time: 15

CPU (currently running):

pid=2, state=RUNNING, start=4, slice=4,

Ready Queue:

EMPTY

Blocked Queue:

EMPTY

Your output to standard out should look exactly the same as this output

(i.e. if I do a di and your program is generating the correct output, then

there will be no dierence between the output your program generates and

the above output format). The output is generated by displaying the system

state after each cpu cycle executes. Basically we print out the system time.

Then we show which process (if any) is currently running on the CPU (or

say it is IDLE if no process is running). Then we display the queue of

processes currently on the Ready and Blocked queues. Note that the queues

are displayed in order. The top of the output corresponds to the head of the

queue. Thus when a new process is dispatched, the next one selected should

be the rst process listed from the ready queue in the previous system cycle.

I have given you some template code (p2-start.cpp) to get you started

The code is meant to be run from the command line, thus from a shell or

dos prompt you would do something like:

$ p2-start simulation-01.sim 5

i.e. the program expects two parameters on the command line, which

should be the name of a le that holds the events to be simulated, and the

value to be used for the time slice quantum. If you need to test your program

and can’t gure out how to invoke running it from the command line, you

can change the line in ‘p2-start.cpp’ to explicitly run a particular simulation

le, like this:

runSimulation(“simulation-01.sim”, time_slice_quantum)

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However, you need to make sure that your program correctly works using

the command line invocation, as shown in `p2-start.cpp`.

I have given some template code to get you started in the le called

p2-start.cpp. I have already provided you with the code needed in order to

correctly parse the command line parameters for the program, and to open

and read in the simulation le events. Your job is to implement the necessary

actions and data structures to handle the simulated events described. The

runSimulation() in ‘p2-start.cpp holds example code and indicates locations

where you need to write your own functions to implement the simulation.

You can use this as a starting point to implement your solution.

Assignment Submission and Requirements

All source les you create for you solution (.c or .cpp/.c++ and .h header

les) should be uploaded to the MyLeo Online submission folder created for

this assignment by the deadline. You should not attach any les besides the

source les containing your C/C++ code. But you should make sure you

attach all needed les you create to your submission, so that I can compile

and run your solution.

You are required to write the program in standard C/C++ programming

language. You should use a relatively recent version of the C/C++ compiler

(C90 C++98 is ne, or the more recent C99 C++11 will also be acceptable),

and/or recent IDE that has an up to date compiler. You should only use

standard C/C++ libraries, do not use Microsoft specic or other third-party

developed external libraries. This page http://en.cppreference.com/w/

provides a good up to date reference of the libraries in the standard C++ and

C languages. You may use the C++ standard template library containers

(like the list and queue items) to implement the ready queue you need. We

will go over a simple implementation of a queue using pointers and/or arrays

in class, if you would like an example implementation in plain C that might

be simpler to use than learning the STL.

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