[. NET] Quick notes on Objective C # (4)-use the framework,

[. NET] Quick notes on Objective C # (4)-use the framework,
Quick notes for Objective C # (4)-use the framework

Var list = new List <int> (); var query = list. where (x => x <150 ). select (x => x. toString (); // query var queryParallel = list in parallel. asParallel (). where (x => x <150 ). select (x => x. toString ());

 

36. Understanding PLINQ in I/O intensive scenarios

Var urls = new List <string> (); foreach (var url in urls) {var result = new WebClient (). downloadData (url); // send a synchronous Web request and wait for receiving data. This mainly wastes time waiting for the Console. writeLine (result);} // use the Parallel processing model Parallel. forEach (urls, url => {var result = new WebClient (). downloadData (url); Console. writeLine (result) ;}); // use PLINQ var results = from url in urls. asParallel () select new WebClient (). downloadData (url); results. forAll (Console. write );

1. The execution method of PLINQ is different from that of Parallel. ForEach () in the Parallel job library. PLINQ uses a fixed number of threads, while Parallel. ForEach () adjusts the number of threads to increase throughput.

2. For those operations that mix I/O-intensive and CPU-intensive, Parallel. ForEach () is more suitable. Parallel. ForEach () dynamically adjusts the number of threads based on the current load. When many threads are blocked due to waiting for I/O operations, Parallel. ForEach () will create more threads to increase throughput. When many threads are working, Parallel. ForEach () also limits the number of active threads and reduces the cost of context switching.

3. for programs that need to access other computers and wait for Remote Response, the parallel task library and PLINQ play an important role.

 

37. Pay attention to exceptions in Parallel Algorithms

1. Exceptions in background threads increase complexity in different aspects. An exception cannot pass through the thread boundary to keep the call stack. When the exception is passed to the method of the start thread, the thread will stop. The call thread cannot capture this error and cannot process it accordingly.

2. Once the background thread throws an exception, other background operations will also stop. It is best not to throw exceptions in parallel algorithms. However, other unexpected exceptions may also occur.

 

This series

Quick notes in Objective C # (1)-C # language habits

Quick notes for Objective C # (2)-. NET resource hosting

Quick notes in Objective C # (III)-use C # To express design

Quick notes for Objective C # (4)-use the framework

 

 

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[Reference] Objective C #