18: Multithreading in C#.NET

Encoding QR in C#.NET 18: Multithreading
18: Multithreading
Denso QR Bar Code Generator In C#.NET
Using Barcode generator for .NET framework Control to generate, create QR Code JIS X 0510 image in .NET applications.
(sequence of instructions) to the next so quickly that it appears the threads are executing simultaneously The period of time that the processor executes a particular thread before switching to another is the time slice or quantum The effect is similar to that of a fiber optic telephone line in which the fiber optic line represents the processor and each conversation represents a thread A (single-mode) fiber optic telephone line can send only one signal at a time, but many people can hold simultaneous conversations over the line The fiber optic channel is fast enough to switch between conversations so quickly that each conversation appears uninterrupted Similarly, each thread of a multithreaded process appears to run continuously with other threads Since a thread is often waiting for various events, such as an I/O operation, switching to a different thread results in more efficient execution, because the processor is not idly waiting for the operation to complete However, switching from one thread to the next does create some overhead If there are too many threads, the switching overhead begins to noticeably affect performance, and adding additional threads will likely decrease performance further; the processor spends time switching from one thread to another instead of accomplishing the work of each thread Even readers new to programming will have heard the term multithreading, most likely in a conversation about its complexity In designing both the C# language and the framework, considerable time was spent on simplifying the programming API that surrounds multithreaded programming However, considerable complexity remains, not so much in writing a program that has multiple threads, but in doing so in a manner that maintains atomicity, avoids deadlocks, and does not introduce execution uncertainty such as race conditions
Barcode Generator In C#
Using Barcode maker for .NET framework Control to generate, create bar code image in .NET applications.
Atomicity
QR Code Encoder In .NET
Using Barcode maker for ASP.NET Control to generate, create QR Code JIS X 0510 image in ASP.NET applications.
Consider code that transfers money from a bank account First, the code verifies whether there are sufficient funds; if there are, the transfer occurs If after checking the funds, a different thread removes the funds, an invalid transfer may occur when execution returns to the initial thread Controlling account access so that only one thread can access the account at a time
Generate QR Code 2d Barcode In Visual Studio .NET
Using Barcode creator for VS .NET Control to generate, create QR image in .NET applications.
18: Multithreading
QR Code Encoder In VB.NET
Using Barcode drawer for .NET Control to generate, create QR Code JIS X 0510 image in .NET framework applications.
fixes the problem and makes the transfer atomic A set of operations is atomic if one of the following two conditions is met:
Barcode Generator In C#.NET
Using Barcode generation for Visual Studio .NET Control to generate, create bar code image in .NET applications.
The entire set of operations must complete before any operation
Drawing Barcode In C#
Using Barcode maker for VS .NET Control to generate, create bar code image in .NET framework applications.
appears to have executed
ANSI/AIM Code 39 Creation In Visual C#
Using Barcode generator for Visual Studio .NET Control to generate, create ANSI/AIM Code 39 image in .NET applications.
The apparent state of the system must return to the state prior to any
Generate ANSI/AIM Code 128 In C#
Using Barcode generation for .NET framework Control to generate, create Code 128B image in VS .NET applications.
operation executing as though no steps executed Returning to the bank transfer example, although composed of multiple steps, the entire set must be one atomic operation In the process of performing each step, no interruptions (such as a debit) should occur until the complete set finishes And if the complete set does not finish, it should appear that none did (you can t debit the money from one account and not credit it to a second, for example) Identifying and implementing atomicity is one of the primary complexities of multithreaded programming Unfortunately, the complexity increases because the majority of C# statements are not atomic Count++, for example, is a simple statement in C#, but it translates to multiple instructions for the processor 1 The processor reads the data in Count 2 The processor calculates the new value 3 Count is assigned a new value (even this may not be atomic) After the data is accessed, but before the new value is assigned, a different thread may modify the original value (perhaps also checking the value prior to modifying it), creating a race condition because the value in Count has, for at least one thread s perspective, changed unexpectedly
DataMatrix Creation In C#.NET
Using Barcode generation for .NET Control to generate, create Data Matrix image in .NET framework applications.
Deadlock
Printing Code 39 Extended In .NET Framework
Using Barcode maker for VS .NET Control to generate, create Code 3/9 image in .NET applications.
To avoid such race conditions, languages support the ability to restrict blocks of code to a specified number of threads, generally one However, if the order of lock acquisition between threads varies, a deadlock could occur such that threads freeze, each waiting for the other to release its lock For example:
Draw ANSI/AIM Code 39 In Visual Basic .NET
Using Barcode generation for .NET framework Control to generate, create Code-39 image in .NET applications.
Generating DataMatrix In .NET
Using Barcode generation for ASP.NET Control to generate, create DataMatrix image in ASP.NET applications.
Code 3/9 Reader In Visual Studio .NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in .NET applications.
Bar Code Maker In Java
Using Barcode maker for Java Control to generate, create barcode image in Java applications.
Paint Barcode In Java
Using Barcode generation for Java Control to generate, create bar code image in Java applications.