Today's Question:  What does your personal desk look like?        GIVE A SHOUT

SEARCH KEYWORD -- multi-thread

  An experience of fixing a memory-corruption bug

During the last 4 months, I was disturbed by a memory-corruption bug, and this bug will cause program crash. Until last Monday, I found the root cause and fixed it. This debug process is a difficult but memorable experience, so I will share it in this article.   My program works as a SMS Hub. When it receives a SMS, it will allocate a structure in heap memory like this: typedef struct { ...... int *a[8]; ...... } info; After processing the SMS, the program will free the m...

   c, debug, unix, solaris, multi-thread     2014-05-04 03:52:43

  JavaScript tutorial - Creating time delays

There are two ways of creating time delays with JavaScript. The first is more simple and will simply wait for a specified amount of time before executing a function. The second does the same but will repeatedly execute the function. Note, many browsers have a minimum delay length of between 25 and 75 ms, with some of the fastest browsers having a minimum delay of about 3 ms. If a shorter delay is specified, the actual delay will be the minimum delay length. Even with higher numbers, the delay i...

   JavaScript,Time delay,setTimeout,setInterval     2012-04-13 07:17:46

  A Solution to CPU-intensive Tasks in IO Loops

Back in October 2011, Ted Dziuba infamously said that Node.js is Cancer.  A provocative title to a provocative article.  The only thing it didn’t really provoke in the commentary was much thought ;)  Zing. My interpretation of the article is that Ted holds up the classic blocking-IO process-per-request (or  thread per request; same difference) model as superior.  Yet we all remember where the blocking-IO forking model got Apache in the early days.  ...

   CPU,Intensive IO loops,Solution,C++     2012-02-06 07:42:40

  Java Concurrency Basics: CountDownLatch and CyclicBarrier

CountDownLatch CountDownLatch can be used in synchronizing behavior among threads, it makes one or more threads wait for some actions in other threads to be completed. It has a property count which defines how many countDown() need to be called before other threads which called await() to be waked up.  When a thread calls CountDownLatch.await(), the thread will be blocked until the value of count becomes 0. The initial value of count can be specified when creating the CountDownLatch instanc...

   JAVA,JAVA CONCURRENCY,COUNTDOWNLATCH,CYCLICBARRIER     2018-03-25 07:02:40

  The Erlang Design Pattern

Over the last couple of weeks I did an OO programming experiment. I call it the Erlang design pattern. It is based on the Actor model but goes some steps further. At its core just like the Actor model there are active entities (objects) that have a thread and a message queue with the thread waiting on the message queue to do some stuff. The Erlang design pattern extends the Actor model by first dividing the software program into active (actors, that have their own thread) and passive ...

   Erlang,Thread,Pattern,OS Threads     2012-02-06 07:47:56

  ConcurrentHashMap vs Collections.synchronizedMap()

ConcurrentHashMap and Collections.synchronizedMap() both provide thread-safe operations of collections of data. They are used in multithreaded programs to provide both thread safety and performance improvements. In many cases, we can use either of them. But the realization of thread safety is different for these two implementations. ConcurrentHashMap will create an HashEntry[] array internally to store the elements passed in from a Map, while Collections.synchronizedMap() will return a Synchroni...

   ConcurrentHashMap,Collections.synchronizedMap     2014-09-18 05:04:59

  The several flavors of random in Java

Random number generation is one of most basic features in any programming language. The basic utilization is always the same: generate a random number between 0 and 1. With such a simple resource at hand we sometimes overlook some interesting features. What do we learn from the books? The most obvious and maybe intuitive way to generate random numbers in Java is simply calling: java.lang.Math.random() Random generation is in the Math utility class with abs, pow, floor...

   Java,Random,Thread,Math,Type     2012-03-22 14:17:44

  Paint messages will come in as fast as you let them

There is a class of messages which are generated on demand rather than explicitly posted into a message queue. If you call Get­Message or Peek­Message and the queue is empty, then the window manager will look to see if one of these generated-on-demand messages is due, messages like WM_TIMER, WM_MOUSE­MOVE, and WM_PAINT. Neil wonders, "In that program that called Invalidate­Rect 100,000 times, how many paint messages were generated?" The Zen answer to this question is "Yes." A ...

   WM_PAINT,paint message,work,Mouse move     2011-12-21 09:37:14

   Python – parallelizing CPU-bound tasks with multiprocessing

In a previous post on Python threads, I briefly mentioned that threads are unsuitable for CPU-bound tasks, and multiprocessing should be used instead. Here I want to demonstrate this with benchmark numbers, also showing that creating multiple processes in Python is just as simple as creating multiple threads. First, let’s pick a simple computation to use for the benchmarking. I don’t want it to be completely artificial, so I’ll use a dumbed-down version of factorization...

   Python,Multitasking,Multiprocessing,CPU bound     2012-01-17 11:38:22

  Python threads: communication and stopping

A very common doubt developers new to Python have is how to use its threads correctly. Specifically, a large amount of questions on StackOverflow show that people struggle most with two aspects: How to stop / kill a threadHow to safely pass data to a thread and back I already have a blog post touching on these issues right here, but I feel it’s too task-specific for sockets, and a more basic and general post would be appropriate. I assume the reader has a basic familiarity with Pytho...

   Python,Multithreading,Communication,Synchronize     2011-12-28 07:38:32

RECENT