Priority-based CPU Scheduler

A Python implementation of a priority-based CPU scheduler using a time-slice model and process blocking intervals.

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Features

• Simulates a CPU scheduling algorithm with priority-based process handling.
• Supports process preemption, blocking, and termination.
• Outputs the simulation timeline, including process states.
• Calculates average turnaround time (TAT) for all processes.
• Handles process arrivals dynamically based on arrival times.
• Configurable time_slice and block_duration values.
• Debug mode (DEBUG flag) for detailed simulation logs.

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Main Functionality

The scheduler manages three key queues:

1. Arrival Queue

   • Stores processes waiting to enter the ready queue based on their arrival times.

2. Ready Queue

   • Holds processes ready for execution, sorted by priority.
   • Processes are preempted at next quantum if a higher-priority process arrives.

3. Blocked Queue

   • Contains processes temporarily halted due to reaching their block intervals.
   • These processes are moved back to the ready queue after their block duration ends.

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Usage

The program requires an input file containing process definitions, and it accepts additional parameters for the time slice and block duration:

Input File Format

Each line in the file represents a process with the following space-separated fields:

• Name: a sequence of non-blank characters representing the name of the process.
• Priority: the priority level for the process, from 1 to 9. A higher number indicates a process should take precedence over lower-numbered priority processes.
• Arrival Time: the time at which the process arrives in the system.
• Total Time: the total amount of CPU time that will be used by the process.
• Block Interval: the interval at which the process will block for I/O. When a process blocks, it is unavailable to run for the time specified by the command line argument block_duration.

Example Input File

# ProcessName Priority ArrivalTime TotalTime BlockInterval
A 1 0 10 3
B 2 2 5 2
C 3 4 7 4

Command-line Execution

python3 scheduler.py <input_file> <time_slice> <block_duration>

Example

python3 scheduler.py joblist2.txt 2 1

• input_file: Path to the input file containing process details.
• time_slice: the decimal integer length of the time slice for the Round-Robin scheduler.
• block_duration: the decimal integer time length that a process is unavailable to run after it blocks.

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Outputs

The scheduler produces a timeline of process events in the following format:

• Start Time: When the event begins.
• Process Name: Identifier for the process or "(IDLE)" if the CPU is idle.
• Duration: Length of the event in time units.
• Status:
  • T: Process terminated (completed all required CPU time).
  • B: Process blocked (reached block interval).
  • P: Process preempted by the time slice.
  • I: CPU idle.

Example Output

timeSlice: 2	blockDuration: 1
0	A	2	P
2	B	2	P
4	C	2	P
6	(IDLE)	1	I
...
Average Turnaround Time: 8.333

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