ITEC 95(SIR ROWEE) Flashcards by Eon Torres

Advantages of Modeling & Simulation

Allows for testing hypothetical scenarios without actual implementation.

Can minimize risks and optimize performance.
Provides a cost-effective solution for solving complex problems.

How well did you know this?

Not at all

Perfectly

Limitations of Modeling & Simulation

Models may not accurately capture real-world behavior.

Can be time-consuming and require expertise to create.
Data availability and quality can greatly affect the accuracy of the simulation.

How well did you know this?

Not at all

Perfectly

: One of the significant advantages of modeling and simulation is that it allows for extensive testing without the need for a physical prototype.

Testing

How well did you know this?

Not at all

Perfectly

Modeling and simulation can also make upgrading an existing system or process more efficient.

Upgrading:

How well did you know this?

Not at all

Perfectly

Another benefit of modeling and simulation is the ability to identify constraints in a system.

Identifying constraints:

How well did you know this?

Not at all

Perfectly

Modeling and simulation can also be useful for diagnosing problems in a system.

Diagnostics:

How well did you know this?

Not at all

Perfectly

Modeling and simulation can handle complex systems and processes that would be difficult to analyze using traditional methods.

Complexity:

How well did you know this?

Not at all

Perfectly

One potential disadvantage of modeling and simulation is that it may not accurately represent the real-world system. This can result in false positives or false negatives during testing.

Testing:

How well did you know this?

Not at all

Perfectly

Another disadvantage is that the simulation may not accurately predict the impact of changes on the system. This can result in unexpected consequences when the changes are made in the physical system.

Upgrading

How well did you know this?

Not at all

Perfectly

Modeling and simulation may also fail to identify constraints that are not included in the model.

Identifying constraints

How well did you know this?

Not at all

Perfectly

Similarly, modeling and simulation may miss problems that are not included in the model.

Diagnostics:

How well did you know this?

Not at all

Perfectly

Modeling and simulation can also be time-consuming and require significant computational resources, particularly for complex systems.

Complexity

How well did you know this?

Not at all

Perfectly

Modeling and simulation can have ethical implications, such as the use of virtual animal testing instead of real-life testing.

Ethical Considerations

How well did you know this?

Not at all

Perfectly

Transparency and accountability are important in the use and development of simulations.

Ethical Considerations

How well did you know this?

Not at all

Perfectly

Advancements in technology such as artificial intelligence and machine learning can improve the accuracy and efficiency of simulation.

Future of Modeling & Simulation

How well did you know this?

Not at all

Perfectly

More widespread use in fields such as urban planning and climate change modeling.

Future of Modeling & Simulation

How well did you know this?

Not at all

Perfectly

Here are some examples of ethical considerations in modeling and simulation:

Data privacy
Bias and discrimination
Safety and reliability
Intellectual property
Transparency and accountability

How well did you know this?

Not at all

Perfectly

The use of modeling and simulation is increasing in many fields, and there is a growing demand for professionals with expertise in this area.

Career Opportunities

How well did you know this?

Not at all

Perfectly

Deciding which process/thread should occupy the resource (CPU, disk, etc)

Process Scheduling

How well did you know this?

Not at all

Perfectly

Switch CPU from one process to another
Performed by scheduler

Context Switch

How well did you know this?

Not at all

Perfectly

Need hardware support

Context Switch

How well did you know this?

Not at all

Perfectly

When should the scheduler be called?

A new process is admitted
The running process exits
The running process is blocked
I/O interrupt (some processes will be ready)
Clock interrupt (every 10 milliseconds)

How well did you know this?

Not at all

Perfectly

The running process keeps the CPU until it voluntarily gives up the CPU
process exits
switches to blocked state
Transition 3 is only voluntar

Non-preemptive scheduling:

How well did you know this?

Not at all

Perfectly

The running process can be interrupted and must release the CPU (can be forced to give up CPU)

Preemptive scheduling

How well did you know this?

Not at all

Perfectly

(equitable shares of CPU)

Fairness

highest priority first)

Priority

make best use of equipment)

Efficiency

(can’t take advantage of the system)

Encouraging good behavior

degrade gracefully

Support for heavy loads

interactive, real-time, multi-media

Adapting to different environments

: keep resources as busy as possible

Efficiency

of processes that complete in unit time

Throughput:

Total amount of time spent by the process waiting in ready queue

Waiting Time

Amount of time spent by the process waiting in ready queue before it starts executing

Initial Waiting Time

amount of time from when a job is admitted until it completes

Response Time

Assign CPU proportionally to given application weight

Proportionality:

Meeting Deadlines

Scheduling should load balance between I/O bound and CPU-bound processes Ideal would be to run all equipment at 100% utilization but that would not necessarily be good for response time

Process Mix

Process that requests the CPU FIRST is allocated the CPU FIRST. Also called _____ Used in Batch Systems Implementation

First Come First Serve (FCFS)

Is it Preemptive or Non-preemptive?

NON-PREEMPTIVE

Problems with FCFS

Non-preemptive Does not minimize AWT Cannot utilize resources in parallel

Usually preemptive Time is sliced into quanta (time intervals) Scheduling decision is also made at the beginning of each quantum Performance Criteria Average response time Average initial waiting time Average waiting time Fairness (or proportional resource allocation) Representative algorithms: Round-robin Priority-based

Interactive Scheduling Algorithms

One of the oldest, simplest, most commonly used scheduling algorithm Select process/thread from ready queue in a round-robin fashion (take turns)

Round-robin

Schedule the job with the shortest computation time first Scheduling in Batch Systems Two types: Non-preemptive Preemptive Optimal if all jobs are available simultaneously: Gives the best possible AWT (average waiting time)

Shortest Job First (SJF)

Shortest job runs first. A job that arrives and is shorter than the running job will preempt it

Preemptive SJF

A job may keep getting preempted by shorter ones

Starvation

A Problem with Preemptive SJF

STARVATION

Examples include Air Combat Training Simulation System, Tactical Air Crew Combat Training System, ZAP Missile Launch, Integrated Air Defense Systems. - Used to train soldiers in a simulated environment that replicates real-life scenarios. - Helps improve decision-making skills and situational awareness of soldiers

Simulation for Training

- Examples include Full Body Vasculature Silicone Model, Vital Sign Simulation, CFD Simulation. - Used to train medical professionals and students in a safe and controlled environment. - Helps improve skills and knowledge in diagnosis, treatment, and surgery.

Simulation for Health and Medicine

- Examples include Multi-physics simulation in ski manufacturing, simulation for fuel injector design and spray. - Used to design and improve engineering systems and products. - Helps predict system behavior, optimize product performance, and reduce costs and production time

Simulation for Engineering

- Simulations in education are somewhat like training simulations. They focus on specific tasks. - a more recent use of simulation in education include animated narrative vignettes (ANV). ANVs are cartoon-like video narratives of hypothetical and reality-based stories involving classroom teaching and learning

Simulation in Education

Discuss how modeling and simulation are used in the telecommunications industry to design and optimize networks, predict and prevent failures, and improve performance.

Simulation in Telecommunications:

Discuss how modeling and simulation are used in business to make decisions, forecast trends, and optimize processes

Simulation in Business:

Discuss how modeling and simulation are used in training and support for various industries, such as healthcare and aviation

Simulation in Training and Support:

Provides a safe and controlled environment for training and experimentation. - Helps improve decision-making skills, knowledge, and performance in various fields. - Reduces costs and production time by optimizing product design and performance

Benefits of Modeling and Simulation

- Allows for testing hypothetical scenarios without actual implementation. - Can minimize risks and optimize performance. - Provides a cost-effective solution for solving complex problems

Advantages of Modeling & Simulation

- Models may not accurately capture real-world behavior. - Can be time-consuming and require expertise to create. - Data availability and quality can greatly affect the accuracy of the simulation.

Limitations of Modeling & Simulation

TT=

CT-AT

WT=

TT-BT

CT=

AT+BT

CPU UTILIZATION=

(TOTAL CT/TOTAL ELAPSED TIME)*100%

Interactive Scheduling Algorithms

One of the oldest, simplest, most commonly used scheduling algorithm Select process/thread from ready queue in a round-robin fashion (take turns)

Round-robin

70-80% of jobs block within time-slice

Heuristic:

10-100 ms (depends on job priority)

Typical time-slice

Too many context switches (overheads) Inefficient CPU utilization

Time slice too small

FIFO behavior Poor initial waiting time

Time slice too large

Schedule the job with the shortest computation time first Scheduling in Batch Systems

Shortest Job First (SJF)

TWO TYPES OF SJF:

Non-preemptive Preemptive

Shortest job runs first. A job that arrives and is shorter than the running job will preempt it

Preemptive SJF

A Problem with Preemptive SJF

Starvation

A job may keep getting preempted by shorter ones

Starvation

time it takes for the dispatcher to stop one process and start another running

Dispatch latency

Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them

CPU Scheduler

gives control of the CPU to the process selected by the scheduler; this involves:

Dispatcher module

keep the CPU as busy as possible

CPU utilization

of processes that complete their execution per time unit

Throughput

amount of time to execute a particular process

Turnaround time

amount of time a process has been waiting in the ready queue

Waiting time

amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment)

Response time

Associate with each process the length of its next CPU burst. Use these lengths to schedule the process with the shortest time.

Shortest-Job-First (SJF) Scheduling

gives minimum average waiting time for a given set of processes

SJF is optimal

A priority number (integer) is associated with each process

Priority Scheduling

The CPU is allocated to the process with the highest priority (smallest integer ≡ highest priority)

Priority Scheduling

low priority processes may never execute

Starvation

as time progresses increase the priority of the process

Aging

Each process gets a small unit of CPU time (time quantum), usually 10-100 milliseconds. After this time has elapsed, the process is preempted and added to the end of the ready queue.

Round Robin (RR)

Ready queue is partitioned into separate queues: foreground (interactive) background (batch) Each queue has its own scheduling algorithm: foreground – RR background – FCFS Scheduling must be done between the queues: Fixed priority scheduling; (i.e., serve all from foreground then from background). Possibility of starvation. Time slice – each queue gets a certain amount of CPU time which it can schedule amongst its processes; i.e., 80% to foreground in RR 20% to background in FCFS

Multilevel Queue

A process can move between the various queues; aging can be implemented this way. Multilevel-feedback-queue scheduler defined by the following parameters:

Multilevel Feedback Queue

Distinction between user-level and kernel-level threads

Many-to-one and many-to-many models, thread library schedules user-level threads to run on LWP Known as process-contention scope (PCS) since scheduling competition is within the process

Thread Scheduling

Kernel thread scheduled onto available CPU is system-contention scope (SCS) – competition among all threads in system

Thread Scheduling

competition among all threads in system

system-contention scope (SCS)

API allows specifying either PCS or SCS during thread creation

Pthread Scheduling

CPU scheduling more complex when multiple CPUs are available

Multiple-Processor Scheduling

only one processor accesses the system data structures, alleviating the need for data sharing

Asymmetric multiprocessing

each processor is self-scheduling, all processes in common ready queue, or each has its own private queue of ready processes

Symmetric multiprocessing (SMP)

process has affinity for processor on which it is currently running

Processor affinity

Recent trend to place multiple processor cores on same physical chip

Multicore Processors

Faster and consume less power

Multicore Processors

Multiple threads per core also growing Takes advantage of memory stall to make progress on another thread while memory retrieve happens

Multicore Processors

Constant order O(1) scheduling time

Linux Scheduling

Two priority ranges: time-sharing and real-time

Linux Scheduling

Real-time range from 0 to 99 and nice value from 100 to 140

Linux Scheduling

takes a particular predetermined workload and defines the performance of each algorithm for that workload

Deterministic modeling