time-clocks

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clock函数的使用方法

clock函数的使用方法clock函数是C语言中的一个库函数，用于计算程序运行时间。

它的使用方法相对简单，但需要掌握一定的编程基础知识。

在本文中，我们将详细介绍clock函数的使用方法。

1. 引入头文件在使用clock函数之前，必须先引入头文件。

在C语言中，我们可以通过以下语句引入头文件：#include <time.h>这条语句将time.h头文件引入到我们的程序中，使我们可以使用time相关的函数和变量。

2. 调用clock函数在程序中调用clock函数非常简单。

我们只需要使用以下语句即可：clock_t start_time = clock();这条语句将获取当前时间，并将其保存在一个名为start_time的变量中。

值得注意的是，clock函数的返回值类型为clock_t，所以start_time的类型也是clock_t。

3. 运行要测试的程序接下来，我们可以运行我们要测试的程序。

在程序运行之后，我们可以再次调用clock函数，获取程序结束时间：clock_t end_time = clock();同样，这条语句将获取当前时间，并将其保存在一个名为end_time的变量中。

4. 计算程序运行时间接下来我们需要通过简单的数学运算计算程序的运行时间。

我们只需要将end_time减去start_time，然后将差值除以CLOCKS_PER_SEC即可。

例如：double total_time = (double)(end_time - start_time) /CLOCKS_PER_SEC;这条语句将计算程序的总运行时间，并将结果保存在一个名为total_time的变量中。

注意，我们需要将end_time和start_time的差值强制转换为double类型，以避免出现整数除法的问题。

此外，CLOCKS_PER_SEC是一个常量，表示每秒钟的时钟嘀嗒数。

我们需要将差值除以该常量，才能得到程序的实际运行时间。

认识钟表的题30道可打印

认识钟表的题30道可打印英文回答：Introduction:Clocks are an essential part of our daily lives. They help us keep track of time and manage our schedules. In this article, I will share 30 printable clock-related questions and answers. So, let's dive in and explore the fascinating world of clocks!1. How does a clock work?A clock works by using a power source, such as a battery or electricity, to move the hands or digits on the clock face. The movement of the hands or digits indicates the passage of time.2. What are the different types of clocks?There are various types of clocks, including analog clocks, digital clocks, wall clocks, alarm clocks, and grandfather clocks. Each type has its own unique features and functions.3. Can you give an example of an analog clock?Sure! An analog clock is a traditional clock with hour, minute, and sometimes second hands. It usually has a circular face with numbers or Roman numerals to indicate the time. An example of an analog clock is the classic round wall clock found in many homes and offices.4. What is a digital clock?A digital clock displays the time using digits, usually in the format of hours and minutes. It is commonly found on electronic devices such as smartphones, computers, and microwaves.5. How accurate are clocks?Clocks can vary in accuracy. Some clocks, like atomic clocks, are incredibly accurate and can measure time to within a fraction of a second. Others, such as mechanical clocks, may have slight variations and require periodic adjustments.6. Can you explain the concept of time zones?Time zones are regions with the same standard time. They are used to simplify timekeeping and ensure that people in different parts of the world are on a similar schedule. For example, if it's 12:00 PM in New York, itwill be a different time in London due to the time zone difference.7. What is the significance of daylight saving time?Daylight saving time is the practice of adjusting the clock forward by one hour during the summer months to extend daylight in the evenings. This allows people to make better use of natural daylight and save energy.8. How do you read a clock?To read a clock, you need to identify the position of the hour hand, minute hand, and sometimes the second hand. The hour hand points to the current hour, the minute hand indicates the minutes, and the second hand shows the seconds.9. Are there any idioms or phrases related to clocks?Yes, there are several idioms and phrases related to clocks. For example, "beat the clock" means to finish a task before a deadline, and "around the clock" means continuously or without stopping.10. Can you give an example of using an idiom related to clocks?Certainly! Let's say I have a project due tomorrow, but I'm running out of time. I might say, "I need to work around the clock to finish this on time!"中文回答：介绍：钟表是我们日常生活中不可或缺的一部分。

Time, Clocks, and the Ordering of Events in a Distributed System

Logical clocks
• No physical time is associated with the clocks. Clocks just assign numbers to events as they happen. The numbers assigned are the times at which events occurred. • Clock Ci ≡ a function which assigns a number Ci a to any event a in process Pi • Clock C ≡ a function which assigns a number C b to any event b in the system where C b = Cj b if b is an event in process Pj . So C represents all the clocks in the system. • For system events to be ordered correctly, the Clock Condition must be satisﬁed: For any events a, b: if a → b then C a < C b . If event a happened before event b, then the clock value assigned to a is less than that assigned to b. • The Clock Condition is satisﬁed if the following two conditions hold: C1. If a and b are events in process Pi and a comes before b, then Ci a < Ci b . C2. If a is the sending of a message by process Pi and b if the receipt of that message by process Pj , then Ci a < Cj b . C1 means that there must be at least a clock tick between any two events in a process. C2 means that there must be at least a clock tick between the sending of a message by a process and its corresponding receipt by another process. • System clocks must satisfy conditions C1 and C2 to satisfy the Clock Condition. For this to happen, system processes must obey the following implementation rules: IR1. Each process Pi increments Ci between any two successive events. IR2. a. If event a is the sending of a message m by process Pi , then the message m contains a timestamp Tm = Ci a . b. Upon receiving message m, process Pj sets Cj greater than or equal to its current value and greater than Tm . IR1 causes events in a process to happen at diﬀerent “logical” times and satisﬁes condition C1. IR2 causes process clocks to be synchronized and satisﬁes condition C2. 2

闹钟的作用英语作文

闹钟的作用英语作文Title: The Significance of Alarm Clocks。

Introduction:Alarm clocks play an essential role in our daily lives, serving as reliable tools to wake us up and ensure we start our day on time. Their significance extends beyond mere timekeeping devices, influencing our productivity, punctuality, and overall well-being.Body:1. Ensuring Punctuality: 。

Alarm clocks are indispensable for ensuring punctuality in our routines. Whether it's waking up for work, school, or appointments, these devices serve as dependable reminders, helping us adhere to schedules and meet commitments promptly. Without alarm clocks, many of uswould struggle to wake up consistently at the required times, leading to tardiness and disruptions in our daily lives.2. Promoting Productivity:By waking us up at predetermined times, alarm clocks help jumpstart our productivity each day. They provide a sense of structure and discipline, encouraging us to get out of bed and begin our tasks efficiently. This regularity fosters a productive mindset, allowing us to tackle our responsibilities with focus and determination. Moreover, the act of setting an alarm the night before can serve as a psychological cue, mentally preparing us for the day ahead and setting a positive tone for our activities.3. Maintaining Health and Well-being:Adequate sleep is crucial for overall health and well-being, and alarm clocks play a vital role in maintaining healthy sleep-wake cycles. By ensuring that we wake up at consistent times, these devices help regulateour internal body clocks, promoting better sleep qualityand overall health. Furthermore, alarm clocks can be programmed to wake us up gradually with gentle sounds or light, mimicking the natural sunrise and easing thetransition from sleep to wakefulness. This gradual awakening can reduce feelings of grogginess and improve our mood and energy levels throughout the day.4. Building Discipline and Responsibility:The act of setting and adhering to alarm schedules instills discipline and responsibility in individuals ofall ages. It teaches us the importance of planning aheadand honoring our commitments, traits that are essential for success in both personal and professional spheres. Moreover, consistent use of alarm clocks fosters a sense of accountability, as we take ownership of our time and prioritize our obligations accordingly.5. Facilitating Time Management:Effective time management is a cornerstone ofsuccess in any endeavor, and alarm clocks serve as valuable tools in this regard. By dividing our day into manageable segments and allocating time for various tasks, we can optimize our productivity and accomplish more in less time. Alarm clocks help us adhere to predetermined schedules, ensuring that we allocate sufficient time to essential activities such as work, study, exercise, and relaxation. This structured approach to time management minimizes procrastination and maximizes efficiency, enabling us to make the most of each day.Conclusion:In conclusion, alarm clocks play a multifaceted role in our lives, transcending their basic function of waking usup in the morning. From promoting punctuality and productivity to maintaining health and fostering discipline, these devices are indispensable tools for managing our time and achieving our goals. By recognizing the significance of alarm clocks and incorporating them into our daily routines, we can enhance our efficiency, well-being, and overall quality of life.。

关于时间点钟的英语作文

关于时间点钟的英语作文Title: Exploring the Significance of Time in Our Lives。

Time is an abstract concept that governs our lives in profound ways. Among the various ways we measure and perceive time, one of the most ubiquitous is the clock. Clocks are not just instruments for telling time; they are symbolic representations of our relationship with time itself. In this essay, we delve into the significance of time as represented by the clock.First and foremost, the clock serves as a practicaltool for organizing our daily activities. From the momentwe wake up to the time we go to bed, our lives arestructured around the ticking hands of the clock. Itdictates when we eat, work, sleep, and engage in leisure activities. Without the clock to regulate our schedules, chaos would ensue, highlighting its indispensable role in modern society.Beyond its practical utility, the clock also holds symbolic significance. It serves as a constant reminder of the passage of time and the fleeting nature of life itself. Every tick of the clock signifies a moment lost to the past, urging us to make the most of the time we have. The inevitability of time's passage instills a sense of urgency, motivating us to pursue our goals and aspirations beforeit's too late.Moreover, different cultures and civilizations throughout history have imbued the clock with various symbolic meanings. In some cultures, the clock represents order and discipline, reflecting societal values of punctuality and efficiency. In others, it symbolizes mortality, reminding us of our limited time on Earth. Regardless of interpretation, the clock serves as auniversal symbol of humanity's attempt to make sense of the passage of time.Interestingly, the invention of the clock has also influenced our perception of time itself. Before the advent of precise timekeeping devices, time was perceived in amore fluid and subjective manner, dictated by natural phenomena such as the movement of the sun and stars. However, with the introduction of clocks, time became standardized and quantifiable, leading to a more regimented approach to time management.Furthermore, the evolution of clock technology has had far-reaching implications for society. The invention of mechanical clocks in medieval Europe revolutionized commerce, facilitating trade and economic growth. The subsequent development of pendulum clocks and then quartz clocks further refined timekeeping accuracy, culminating in the atomic clock, which is accurate to within a few billionths of a second.In the digital age, the proliferation of digital clocks and smartphones has made time even more omnipresent in our lives. We are constantly bombarded with notifications, reminders, and alarms, further emphasizing the importance of time management. However, this constant exposure to time can also lead to stress and anxiety, as we feel pressured to constantly optimize our time and productivity.In conclusion, the clock is much more than a mere instrument for telling time; it is a symbol of humanity's relationship with time itself. From its practical utility in organizing our daily lives to its symbolic significance in representing the passage of time, the clock plays a central role in shaping our perception of time. As we continue to navigate the complexities of modern life, it is essential to reflect on the profound significance of time as represented by the clock.。

钟的英语作文

钟的英语作文Clocks: A Brief History and Their Importance in Modern Life。

Clocks have been an essential part of human life for centuries. From the earliest sundials to the modern digital watches, clocks have evolved and adapted to suit the needs of society. In this article, we will explore the history of clocks, their various types, and their importance in modern life.The earliest form of clock was the sundial, which was used by the ancient Egyptians and Greeks over 3,500 years ago. Sundials were simple instruments that used theposition of the sun to tell time. They consisted of a flat surface with a raised gnomon that cast a shadow onto the surface, indicating the time of day. However, sundials could only be used during the day and were not accurate during cloudy or rainy weather.The next major advancement in clock technology was the water clock, which was invented by the ancient Greeks around 325 BC. Water clocks used the flow of water to measure time. They consisted of a container with a small hole at the bottom, which allowed water to flow out at a constant rate. The water level in the container would gradually decrease, indicating the passage of time. Water clocks were much more accurate than sundials and could be used both day and night.In the Middle Ages, mechanical clocks were developed in Europe. These clocks used a pendulum or balance wheel to regulate the movement of the clock hands. Mechanical clocks were much more accurate than water clocks and could be made smaller, allowing them to be used in homes and churches.In the 20th century, electronic clocks were developed, which used electricity to regulate their movement. Electronic clocks were even more accurate than mechanical clocks and could be made even smaller. Today, most clocks are digital and use quartz crystals to keep time.Clocks are used for a variety of purposes in modern life. They are used to tell time, of course, but they also have many other uses. Clocks are used in schools to keep students on schedule, in factories to regulate production, and in hospitals to monitor patients' vital signs. Clocks are also used in sports to time events and intransportation to keep schedules on track.In conclusion, clocks have come a long way since the ancient sundials. From water clocks to mechanical clocks to electronic clocks, they have evolved and adapted to suit the needs of society. Today, clocks are an essential part of modern life, used for a variety of purposes. Without clocks, our lives would be much more chaotic and disorganized.。

认识钟表专项训练题可打印

认识钟表专项训练题可打印英文回答：Clocks are an essential part of our daily lives. They help us keep track of time and ensure that we are punctual for our appointments and deadlines. In this specialized training, I will provide you with printable clock exercises to help you improve your understanding of clocks and time.Firstly, let's start with the basics. A clock consists of two hands the hour hand and the minute hand. The hour hand is shorter and moves slowly, indicating the current hour. The minute hand is longer and moves faster, showing the minutes. Together, they work in harmony to tell us the time.To practice reading clocks, I have prepared a set of printable exercises. Each exercise will display a clock face with the hour and minute hands in different positions. Your task is to determine the time shown on the clock andwrite it down. For example, if the hour hand is pointing at 3 and the minute hand is pointing at 12, the time would be 3 o'clock. Take your time and try to solve each exercise accurately.In addition to reading clocks, it is also important to understand the concept of time intervals. Time intervals refer to the duration between two specific points in time. For instance, if an event starts at 2 o'clock and ends at 4 o'clock, the time interval would be 2 hours.To practice calculating time intervals, I have included exercises that require you to determine the duration between two given times. For example, if an event starts at 9 o'clock and ends at 11 o'clock, the time interval would be 2 hours. These exercises will help you sharpen your time calculation skills.Furthermore, I have included exercises that involve converting time between different units. This will help you become more familiar with various time measurements. For instance, converting minutes to hours or hours to seconds.These exercises will provide you with a comprehensive understanding of time and its measurements.Lastly, I have included some word problems related to clocks and time. These problems will test your ability to apply your knowledge of clocks in real-life scenarios. For example, calculating the time it takes for someone to travel from one place to another given their average speed and distance.中文回答：钟表是我们日常生活中不可或缺的一部分。

用英语介绍时钟的作文

用英语介绍时钟的作文英文回答：Clocks are an essential part of our daily lives. They help us keep track of time and ensure that we are punctual for our appointments and commitments. There are various types of clocks, ranging from traditional analog clocks to modern digital clocks. Each type has its own unique features and advantages.Analog clocks have been around for centuries and are still widely used today. They typically have a circular face with numbered hour markers and rotating hands. The hour hand indicates the hour, while the minute hand shows the minutes. Some analog clocks also have a second hand that moves continuously around the clock face. One of the advantages of analog clocks is that they provide a visual representation of the passage of time. By glancing at the position of the hands, we can quickly determine the approximate time. For example, if the minute hand ispointing at the 6 and the hour hand is between the 3 and the 4, we can infer that it is around 3:30. Analog clocks are also often considered more aesthetically pleasing and can serve as decorative items in our homes or offices.On the other hand, digital clocks have become increasingly popular in recent years. Instead of using rotating hands, digital clocks use electronic displays to show the time in numerical format. They often have additional features such as alarms, timers, and even temperature displays. Digital clocks are known for their accuracy and precision. They provide an exact representation of the time, down to the second. This can be particularly useful in situations where precise timing is required, such as in scientific experiments or sports events. Additionally, digital clocks are often equipped with backlighting, making them easier to read in the dark. For example, if I wake up in the middle of the night and want to check the time, I can simply glance at the digital clock on my bedside table without having to turn on the lights.中文回答：时钟是我们日常生活中不可或缺的一部分。

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CMPS372:Advanced Operating Systems Instructor:Paul C.Attie Department of Computer Science American University of Beirut Lecture13March27,2007 Time,clocks and the ordering of events in a distributed system1OverviewSeminal paper by Leslie Lamport:Time,clocks and the ordering of events in a distributed system.Leslie Lamport.CACM21(7), 1978.Deﬁned the very important concepts of“causal order”and“logical clock”.Very widely used in distributed computing.Key idea:deﬁne a happened before relation→on events in a distributed system.Event a→b means a“happened before”b→is a binary relation on the set of events that occur in a(computation of)a distributed system.→can be“computed”online by useing logical clocks.System model:aﬁxed number of sequential processes communicating by asynchronous message passing.Each process is a sequence of events.An event can be either a local computation event or a message send or a message receive.We are not interested in analyzing local computation,so we allow a local computation event to be anything from the execution of a single instruction to the execution of a procedure.2The“happened before”relation→Deﬁnition.a→b is the smallest irreﬂexive binary relation that satisﬁes all of the following:1.a and b are events in the same process,and a precedes b.2.a is the send of a message,and b is the receipt of the same message.3.there exists event c such that a→c and c→b.Clause3implies that→is transitive.Roughly,a→b means that a“can aﬀect”b.Thus,→is sometimes called“causal dependence”. Deﬁnition.If a→b and b→a,then a and b are concurrent.We assume that a→a,i.e.,an event does not precede itself.Thus→is an irreﬂexive partial ordering on the events in a system.Causal ordering:a→b iﬀit is possible for a to causally aﬀect b,e.g.,by producing a value that is used by b.If a and b are concurrent,then neither can aﬀect the other.2.1Connection to Special RelativitySpecial relativity deﬁnes causality in terms of the mesages(signals)that could be sent—the light cone mports deﬁnes it using the messages that actually are sent.This makes more sense for a software system.3Logical ClocksClock C i for process P i is a mapping of P i’s events to numbers:event a of P i mapped to C i(a). Global clock C:C(a) C i(a)iﬀa is an event of P i,Useful notation when the process is unspeciﬁed.A system of clocks is correct iﬀit satisﬁes:Clock condition:if a→b then C(a)<C(b)We ensure the clock condition by ensuring in turn:C1.If a and b are events in process P i and a comes before b,then C i(a)<C i(b)C2.If a is the sending of a message by process P i and b is the receipt of that message by process P j,then C i(a)<C j(b).We implement C1and C2using implementations rules IR1and IR2respectively,which are given below.We use the variable clock i to store the“current”clock valueof process P i.IR1.Each process P i increments clock i between any two successive events.To meet condition C2,we require that each message m contain a timestamp which equals the time at which the message was sent.Upon receiving a message,a process must advance its clock to be later than the timestamp:IR2.(a)If event a is the sending of a message m by process P i,then the message m contains timestamp C i(a).(b)Upon receiving a message m,process P j sets clock j greater than or equal to its presentvalue and greater than the timestamp of m.4Imposing a Total Order on EventsSometimes having a total order⇒on events is useful.Do this by ordering events accorind to the logical times,and using a static ordering on process names to break ties:Deﬁnition.Let a be an event in process P i and b be an event in process P j.Then a⇒b if and only if either(i)C i(a)<C j(b)or(ii)C i(a)<C j(b)and i<j.⇒extends the partial order→into a total order.4.1Distributed Mutual ExclusionCan use to solve distributed mutual exclusion problem:all request and release operations(of the critical reqsource)by a process are broadcast to all processes,which use⇒to deﬁne a totalorder.Requests are granted in the order of⇒,with older requests being grantedﬁrst(this assures starvation-freedom).Actual implementation uses queues.See Lamports paper for details.The key idea is that P i gets the resource when it knows that its request is older(i.e.,smaller w.r.t.⇒)than any other request that it has received,and it has received a later message from every other process(i.e.,follows P i’s request in⇒).This latter condition means that P i knows that it will not ever receive a request from another process that is earlier than its own outstanding request.Hence P i knows that its requests is the oldest outstanding request in the system,and so can go ahead and grant the request.。