How Threads differ from processes.Why threads are required.
An application consists of one or more processes. A process, in the simplest terms, is an executing program. One or more threads run in the context of the process. A thread is the basic unit to which the operating system allocates processor time. A thread can execute any part of the process code, including parts currently being executed by another thread.
Both threads and processes are methods of parallelizing an application. However, processes are independent execution units that contain their i) own state information, use their ii)own address spaces, and iii)only interact with each other via interprocess communication mechanisms (generally managed by the operating system). Applications are typically divided into processes during the design phase, and a master process explicitly spawns sub-processes when it makes sense to logically separate significant application functionality. Processes, in other words, are an architectural construct.
Review 2:
By contrast, a thread is a coding construct that doesn't affect the architecture of an application. A single process might contains multiple threads; all threads within a process share the i)same state and ii)same memory space, and iii)can communicate with each other directly, because they share the same variables.
Threads typically are spawned for a short-term benefit that is usually visualized as a serial task, but which doesn't have to be performed in a linear manner (such as performing a complex mathematical computation using parallelism, or initializing a large matrix), and then are absorbed when no longer required. The scope of a thread is within a specific code module—which is why we can bolt-on threading without affecting the broader application.
An application consists of one or more processes. A process, in the simplest terms, is an executing program. One or more threads run in the context of the process. A thread is the basic unit to which the operating system allocates processor time. A thread can execute any part of the process code, including parts currently being executed by another thread.
Threads are more light weight, and for the making several "workers" just to utilize all availabe CPUs or cores, you're better of with threads.
When you need the workers to be better isolated and more robust, like with most servers, go with sockets. When one thread crashes badly, it usually takes down the entire process, including other threads working in that process. If a process turns sour and dies, it doesn't touch any other process, so they can happily go on with their bussiness as if nothing happened.
Review 3:
Process is an executing instance of an application. For example, when you double-click the Microsoft Word icon, you start a process that runs Word. A thread is a path of execution within a process. Also, a process can contain multiple threads. When you start Word, the operating system creates a process and begins executing the primary thread of that process.
It’s important to note that a thread can do anything a process can do. But since a process can consist of multiple threads, a thread could be considered a ‘lightweight’ process. Thus, the essential difference between a thread and a process is the work that each one is used to accomplish. Threads are used for small tasks, whereas processes are used for more ‘heavyweight’ tasks – basically the execution of applications.
Another difference between a thread and a process is that threads within the same process share the same address space, whereas different processes do not. This allows threads to read from and write to the same data structures and variables, and also facilitates communication between threads. Communication between processes – also known as IPC, or inter-process communication – is quite difficult and resource-intensive.
If we were dealing with an application that uses only one thread, then the application would only be able to do one thing at a time – so printing and responding to user input at the same time would not be possible in a single threaded application.
When you need the workers to be better isolated and more robust, like with most servers, go with sockets. When one thread crashes badly, it usually takes down the entire process, including other threads working in that process. If a process turns sour and dies, it doesn't touch any other process, so they can happily go on with their bussiness as if nothing happened.
Review 3:
Process is an executing instance of an application. For example, when you double-click the Microsoft Word icon, you start a process that runs Word. A thread is a path of execution within a process. Also, a process can contain multiple threads. When you start Word, the operating system creates a process and begins executing the primary thread of that process.
It’s important to note that a thread can do anything a process can do. But since a process can consist of multiple threads, a thread could be considered a ‘lightweight’ process. Thus, the essential difference between a thread and a process is the work that each one is used to accomplish. Threads are used for small tasks, whereas processes are used for more ‘heavyweight’ tasks – basically the execution of applications.
Another difference between a thread and a process is that threads within the same process share the same address space, whereas different processes do not. This allows threads to read from and write to the same data structures and variables, and also facilitates communication between threads. Communication between processes – also known as IPC, or inter-process communication – is quite difficult and resource-intensive.
MultiThreading
Threads, of course, allow for multi-threading. A common example of the advantage of multithreading is the fact that you can have a word processor that prints a document using a background thread, but at the same time another thread is running that accepts user input, so that you can type up a new document.If we were dealing with an application that uses only one thread, then the application would only be able to do one thing at a time – so printing and responding to user input at the same time would not be possible in a single threaded application.
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