156 lines
6.5 KiB
Python
156 lines
6.5 KiB
Python
#!/usr/bin/env python3
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"""
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最短作业优先调度算法 (SJF/SRTF)
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Shortest Job First / Shortest Remaining Time First
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支持 IO 模拟
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"""
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from typing import List, Dict
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from collections import deque
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import heapq
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from base import (
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Process,
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ProcessScheduler,
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generate_random_processes,
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print_processes
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)
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class SJFScheduler(ProcessScheduler):
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"""最短作业优先调度 (SJF/SRTF)
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SJF: 非抢占式，选择剩余时间最短的进程
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SRTF: 抢占式，选择剩余时间最短的进程
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支持 IO 模拟
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"""
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def __init__(self, processes: List[Process], preemptive: bool = False):
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super().__init__(processes)
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self.preemptive = preemptive
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def schedule(self) -> Dict:
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"""SJF/SRTF 调度算法 (支持IO模拟)"""
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all_processes = list(self.processes)
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for p in all_processes:
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self.init_process(p, p.arrival_time)
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events = []
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for p in all_processes:
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heapq.heappush(events, (p.arrival_time, 'arrival', id(p), p))
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ready_queue = []
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completed = []
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current_time = 0
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while len(completed) < len(all_processes):
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while events and events[0][0] <= current_time:
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event_time, event_type, uid, p = heapq.heappop(events)
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if event_type == 'arrival':
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p.status = self.STATUS_READY
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ready_queue.append(p)
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elif event_type == 'io_complete':
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if p.status == self.STATUS_IO_WAIT:
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p.status = self.STATUS_READY
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ready_queue.append(p)
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if not ready_queue:
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if events:
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current_time = events[0][0]
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continue
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else:
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break
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ready_queue.sort(key=lambda p: (p.remaining_cpu_time, id(p)))
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if self.preemptive:
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# SRTF: 一次只执行1个时间单位，随时检查新到达进程
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current_process = ready_queue[0]
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if current_process.start_time == -1:
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current_process.start_time = current_time
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current_process.status = self.STATUS_RUNNING
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if current_process.current_cpu_idx < len(current_process.cpu_bursts):
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cpu_burst = current_process.cpu_bursts[current_process.current_cpu_idx]
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exec_t = 1 # 每次只执行1单位
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self.gantt_chart.append((current_time, current_process.pid, 'CPU', exec_t))
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current_time += exec_t
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current_process.remaining_cpu_time -= exec_t
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cpu_burst -= exec_t
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current_process.cpu_bursts[current_process.current_cpu_idx] = cpu_burst
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if cpu_burst == 0:
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ready_queue.pop(0) # CPU burst完成，移出就绪队列
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current_process.current_cpu_idx += 1
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io_idx = current_process.current_cpu_idx - 1
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if io_idx < len(current_process.io_bursts):
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io_time = current_process.io_bursts[io_idx]
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current_process.status = self.STATUS_IO_WAIT
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heapq.heappush(events, (current_time + io_time, 'io_complete', id(current_process), current_process))
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else:
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current_process.status = self.STATUS_TERMINATED
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current_process.completion_time = current_time
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self.calculate_metrics(current_process, current_time)
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completed.append(current_process)
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else:
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current_process.status = self.STATUS_READY
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else:
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ready_queue.pop(0)
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current_process.status = self.STATUS_TERMINATED
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current_process.completion_time = current_time
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self.calculate_metrics(current_process, current_time)
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completed.append(current_process)
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else:
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# SJF 非抢占: 一次执行完整CPU burst
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current_process = ready_queue.pop(0)
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if current_process.start_time == -1:
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current_process.start_time = current_time
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current_process.status = self.STATUS_RUNNING
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if current_process.current_cpu_idx < len(current_process.cpu_bursts):
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cpu_burst = current_process.cpu_bursts[current_process.current_cpu_idx]
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self.gantt_chart.append((current_time, current_process.pid, 'CPU', cpu_burst))
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current_time += cpu_burst
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current_process.remaining_cpu_time -= cpu_burst
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current_process.current_cpu_idx += 1
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io_idx = current_process.current_cpu_idx - 1
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if io_idx < len(current_process.io_bursts):
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io_time = current_process.io_bursts[io_idx]
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current_process.status = self.STATUS_IO_WAIT
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heapq.heappush(events, (current_time + io_time, 'io_complete', id(current_process), current_process))
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else:
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current_process.status = self.STATUS_TERMINATED
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current_process.completion_time = current_time
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self.calculate_metrics(current_process, current_time)
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completed.append(current_process)
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else:
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current_process.status = self.STATUS_TERMINATED
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current_process.completion_time = current_time
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self.calculate_metrics(current_process, current_time)
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completed.append(current_process)
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self.results = completed
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algo_name = "SRTF (最短剩余时间优先)" if self.preemptive else "SJF (最短作业优先)"
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return self.print_results(algo_name)
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if __name__ == "__main__":
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processes = generate_random_processes(n=5, seed=42, io_probability=0.5)
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print_processes(processes, "测试数据")
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print("\n--- SJF (非抢占) ---")
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scheduler = SJFScheduler(processes, preemptive=False)
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scheduler.schedule()
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