同類型文章 利用python畫出動態高優先權優先調度
SJF算法:
最短作業優先(SJF)調度算法將每個進程與其下次 CPU 執行的長度關聯起來。實際上,短進程/作業(要求服務時間最短)在實際情況中佔有很大比例,爲了使得它們優先執行,追求最少的平均等待時間時間、平均週轉時間、平均帶權週轉時間。短作業優先可能導致長作業一直得不到處理)
總體構想
用python繪圖這個想法產生於寫調度圖作業那段時間。當時就想着用python繪圖,有兩個想法trutle動態繪製調度圖,還有就是現在所使用的方法。爲什麼用類寫這次的作業,一是下次的作業可以直接繼承SJF類,然後修改調度函數和排序函數就行了。二是用類寫代碼解決一類問題,代碼看起來比較漂亮。
算法設計結構圖
程序執行結果圖
作業信息
作業名 | 到達時間 | 運行時間 |
A | 0 | 5 |
B | 1 | 4 |
C | 2 | 1 |
D | 4 | 2 |
E | 5 | 1 |
基本思路
(1)類初始化:
對於進程調度SJF算法這個類,首先我們需要有成員變量,也就是大致所需要的成員變量。 基本也就需要這麼多。
self.data = [] | 存儲進程 |
self.name = '' |
進程名字 |
self.service_time = 0 |
服務時間 |
self.arrival_time = 0 |
到達時間 |
self.state = '' |
初始狀態 |
self.number = 0 |
進程數量 |
self.timeout = 0 |
超時限定 |
self.start = 0 |
開始時間 |
self.end = 0 |
結束時間 |
def __init__(self):
super(Solution, self).__init__()
# save tasks
self.data = []
self.name = ''
self.service_time = 0
self.arrival_time = 0
self.state = ''
self.number = 0
self.timeout = 0
self.start = 0
self.end = 0
(2)獲取數據:
獲取數據可以從文件(如.txt)中讀入,亦可以從console讀入。這裏要求一個地方,就是數據的格式,名字,到達時間,服務時間。中間用空格分開。如下面表格:
name |
arrival_time |
service_time |
A |
0 |
5 |
B |
1 |
4 |
C |
2 |
1 |
D |
4 |
2 |
E |
5 |
1 |
def get_data_file(self):
with open('data.txt', "r", encoding="utf-8") as file:
for line in file.read().splitlines():
name, arrival_time, service_time = line.split()
# insert the task
self.insert_data(name, arrival_time, service_time)
file.close()
# initial queue
# sort first arrival_time and second service_time
self.data.sort(key=lambda x: (x['arrival_time'], x['service_time']))
# update and recode id
for i in range(self.number):
self.data[i]['index'] = i
def get_data_input(self):
print('How many tasks do you want input?')
tasks_number = int(input('Please enter an integer of type int:'))
print('Please enter name and arrival_time and service_time of task')
print('such as:A 0 5')
for _ in range(tasks_number):
name, arrival_time, service_time = input('Please enter\n').split()
self.insert_data(name, arrival_time, service_time)
# initial queue
# sort first arrival_time and second service_time
self.data.sort(key=lambda x: (x['arrival_time'], x['service_time']))
# update and recode id
for i in range(self.number):
self.data[i]['index'] = i
(3)進行調度:
也就是設計算法,來實現SJF。基本的算法思路,就是維護一個優先隊列。如圖:
每次調度的時候根據需要,然後更新信息,更改作業的狀態和到達和結束的時間。同時獲取下一個或者多個作業,這裏需要考慮到一種情況,就是當前時間片不能獲取下一個作業,需要等待一段時間作業到達,才能執行。這種情況特判一下。然後執行排序,維護這個優先隊列。
def implement(self):
'''start algorithm'''
# get first task
data = [self.data[0]]
# update the time of start
self.start = self.end = data[0]['arrival_time']
while data:
# update information
self.update_information(
data[0]['index'], self.end, self.end + data[0]['service_time'])
# get next task or tasks
data += self.get_next_data(data.pop(0)['index'], data)
# maintain the queue
data = self.sort_data(data)
self.data.sort(key=lambda x: x['id'])
(4)排序和信息更新:
對於排序的實現其實很簡單,前面的結構圖也已經展示了,對於SJF算法一共有兩種排序方式,分別在不同的過程進行使用。數據更新就是更新原始的數據,包括計算狀態,開始時間,結束時間,週轉時間,平均週轉時間等等。
def update_information(self, index, start, end):
self.data[index]['start'] = start
self.data[index]['end'] = end
self.data[index]['state'] = 'f'
self.data[index]['turnaround_time'] = end - \
self.data[index]['arrival_time']
self.data[index]['authorized_turnover_time'] = self.data[index]['turnaround_time'] / \
self.data[index]['service_time']
self.start = start
self.end = end
self.show_data_running(start, end, self.data[index])
(5)數據輸出:
爲什麼要數據輸出,其實這就是一個數據可視化的一種方法。也就是直觀的表達各種信息。所以數據輸出部分,就是自己設置自己的排版,佈局,可以利用\t製表符來打表。
def show_data(self):
print("{:<6}{:<10}{:<10}{:<10}{:<6}{:<8}{:<7}{:<6}".format(
'name', 'arr_time', 'ser_time', 'state', '週轉時間', '帶權週轉時間', 'start', 'end'))
for task in sorted(self.data, key=lambda x: x['id']):
print("{:<6}{:<10}{:<10}{:<10}{:<10}{:<14.2f}{:<7}{:<4}".format(
task['name'],
task['arrival_time'],
task['service_time'],
task['state'],
task['turnaround_time'],
task['authorized_turnover_time'],
task['start'],
task['end']))
(6)plt生成調度圖展示:
利用python的第三方庫,根據數據進行繪圖,然後展示出好看的圖片。
def init_image(self):
# size = 1000 * 500
plt.figure('SJF', figsize=(10, 5))
self.drow_image()
# setting xticks for 0 to self.end + 2
plt.xticks([i for i in range(self.end + 3)])
# setting title
plt.title('the time of task about SJF')
plt.xlabel('')
plt.ylabel('tasks')
# setting yticks.such as A == 0
plt.yticks(self.get_y_ticks()[0], self.get_y_ticks()[1])
def drow_image(self):
for task in self.data:
# the time line of task from start to end
plt.plot([task['start'], task['end']],
[task['id'], task['id']],
label=task['name'],
lw=2)
# annotation of the key point
plt.plot([task['end'], task['end']],
[-1, task['id']],
'k--',
lw=1)
# legend
plt.legend(loc='best')
def set_ax(self):
ax = plt.gca() # 獲取到當前座標軸信息
ax.spines['right'].set_color('none')
ax.spines['bottom'].set_color('none')
ax.xaxis.set_ticks_position('top') # 將X座標軸移到上面
ax.invert_yaxis() # 反轉Y座標軸
ax.grid(True, linestyle='-.') # 網格
def show_image(self):
self.init_image()
self.set_ax()
plt.savefig('SJF.png', dpi=300)
plt.show()
程序執行過程:
支持兩種輸入方式,手動輸入和數據導入。
數據導入:
原始數據
調度前:
調度中:
調度後:
生成調度圖:
手動輸入數據:
調度前
調度中
調度後
生成調度圖:
程序源代碼:
# -*- coding: utf-8 -*-
# @Author: wfy
# @Date: 2020-04-10 15:31:44
# @Last Modified by: wfy
# @Last Modified time: 2020-04-14 13:46:31
import matplotlib.pyplot as plt
class Solution():
"""to achieve SJF"""
def __init__(self):
super(Solution, self).__init__()
# save tasks
self.data = []
self.name = ''
self.service_time = 0
self.arrival_time = 0
self.state = ''
self.number = 0
self.timeout = 0
self.start = 0
self.end = 0
def insert_data(self, name, arrival_time, service_time):
self.data.append({
'id': self.number,
'name': name,
'arrival_time': int(arrival_time),
'service_time': int(service_time),
'state': 'w',
'turnaround_time': 0,
'authorized_turnover_time': 0,
'start': 0,
'end': 0
})
self.timeout = max(self.timeout, int(arrival_time))
self.number += 1
def get_data_file(self):
with open('data.txt', "r", encoding="utf-8") as file:
for line in file.read().splitlines():
name, arrival_time, service_time = line.split()
# insert the task
self.insert_data(name, arrival_time, service_time)
file.close()
# initial queue
# sort first arrival_time and second service_time
self.data.sort(key=lambda x: (x['arrival_time'], x['service_time']))
# update and recode id
for i in range(self.number):
self.data[i]['index'] = i
def get_data_input(self):
print('How many tasks do you want input?')
tasks_number = int(input('Please enter an integer of type int:'))
print('Please enter name and arrival_time and service_time of task')
print('such as:A 0 5')
for _ in range(tasks_number):
name, arrival_time, service_time = input('Please enter\n').split()
self.insert_data(name, arrival_time, service_time)
# initial queue
# sort first arrival_time and second service_time
self.data.sort(key=lambda x: (x['arrival_time'], x['service_time']))
# update and recode id
for i in range(self.number):
self.data[i]['index'] = i
def show_data_running(self, start, end, data):
print('-'*40)
print("from {:} to {:}".format(start, end))
print("task name:{:}".format(data['name']))
print("task state:{:}\n".format('R'))
def show_data(self):
print("{:<6}{:<10}{:<10}{:<10}{:<6}{:<8}{:<7}{:<6}".format(
'name', 'arr_time', 'ser_time', 'state', '週轉時間', '帶權週轉時間', 'start', 'end'))
for task in sorted(self.data, key=lambda x: x['id']):
print("{:<6}{:<10}{:<10}{:<10}{:<10}{:<14.2f}{:<7}{:<4}".format(
task['name'],
task['arrival_time'],
task['service_time'],
task['state'],
task['turnaround_time'],
task['authorized_turnover_time'],
task['start'],
task['end']))
def cmp(self):
'''the method of sort'''
return lambda x: (x['service_time'], x['arrival_time'], x['index'])
def sort_data(self, data):
return sorted(data, key=self.cmp())
def update_information(self, index, start, end):
self.data[index]['start'] = start
self.data[index]['end'] = end
self.data[index]['state'] = 'f'
self.data[index]['turnaround_time'] = end - \
self.data[index]['arrival_time']
self.data[index]['authorized_turnover_time'] = self.data[index]['turnaround_time'] / \
self.data[index]['service_time']
self.start = start
self.end = end
self.show_data_running(start, end, self.data[index])
def get_next_data(self, index, data):
# get tasks from the beginning to the end of the current task
result = [x for x in self.data if x['arrival_time'] <=
self.end and x['state'] == 'w' and x not in data]
if result or data:
return result
# no tasks entered at current time
for task in self.data:
if task['state'] == 'w':
self.start = self.end = task['arrival_time']
return [task]
return []
def implement(self):
'''start algorithm'''
# get first task
data = [self.data[0]]
# update the time of start
self.start = self.end = data[0]['arrival_time']
while data:
# update information
self.update_information(
data[0]['index'], self.end, self.end + data[0]['service_time'])
# get next task or tasks
data += self.get_next_data(data.pop(0)['index'], data)
# maintain the queue
data = self.sort_data(data)
self.data.sort(key=lambda x: x['id'])
def get_y_ticks(self):
return [x['id'] for x in self.data] + [self.data[-1]['id'] + 1], [x['name'] for x in self.data] + ['']
def init_image(self):
# size = 1000 * 500
plt.figure('SJF', figsize=(10, 5))
self.drow_image()
# setting xticks for 0 to self.end + 2
plt.xticks([i for i in range(self.end + 3)])
# setting title
plt.title('the time of task about SJF')
plt.xlabel('')
plt.ylabel('tasks')
# setting yticks.such as A == 0
plt.yticks(self.get_y_ticks()[0], self.get_y_ticks()[1])
def drow_image(self):
for task in self.data:
# the time line of task from start to end
plt.plot([task['start'], task['end']],
[task['id'], task['id']],
label=task['name'],
lw=2)
# annotation of the key point
plt.plot([task['end'], task['end']],
[-1, task['id']],
'k--',
lw=1)
# legend
plt.legend(loc='best')
def set_ax(self):
ax = plt.gca() # 獲取到當前座標軸信息
ax.spines['right'].set_color('none')
ax.spines['bottom'].set_color('none')
ax.xaxis.set_ticks_position('top') # 將X座標軸移到上面
ax.invert_yaxis() # 反轉Y座標軸
ax.grid(True, linestyle='-.') # 網格
def show_image(self):
self.init_image()
self.set_ax()
plt.savefig('SJF.png', dpi=300)
plt.show()
def main(self):
if input('Do you want get data by file? y/Y or n/N\n') in ['y', 'Y']:
SJF.get_data_file()
else:
SJF.get_data_input()
SJF.show_data()
SJF.implement()
SJF.show_data()
SJF.show_image()
if __name__ == '__main__':
try:
SJF = Solution()
SJF.main()
except Exception as e:
print('An exception', e)
else:
print('Finish')
finally:
print('finally')