AtomicInteger | 易学教程

Performance Difference of AtomicInteger vs Integer

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问题 Is there any performance difference between AtomicInteger and Integer ? 回答1: The choice of these two types should not depend on the performance. The main choice for AtomicInteger is if you want to achieve thread safety with the operations on the integer. However the performace difference might strongly depend on the choosen operating system, as the detailed implementation of atomic operations depend on the operating system. 回答2: AtomicInteger allows some (not all!) operations that would

Performance Difference of AtomicInteger vs Integer

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原子变量与synchronized详细解释

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AtomicInteger，一个提供原子操作的Integer的类。在Java语言中，++i和i++操作并不是线程安全的，在使用的时候，不可避免的会用到synchronized关键字。而AtomicInteger则通过一种线程安全的加减操作接口。要使用多处理器系统的功能，通常需要使用多线程构造应用程序。但是正如任何编写并发应用程序的人可以告诉你的那样，要获得好的硬件利用率，只是简单地在多个线程中分割工作是不够的，还必须确保线程确实大部分时间都在工作，而不是在等待更多的工作，或等待锁定共享数据结构。而synchronized来控制并发就需要去等待这个锁资源，这步是非常消耗资源的，处理的吞吐量也就下去了。而java的concurrent 并发包提供的AtomicInteger就提供CAS原理避免了锁等待，具体的实现是通过UnSafe类来直接操作底层的硬件资源。 cpu 硬件同步原语(compare and swap) 支持并发的第一个处理器提供原子的测试并设置操作，通常在单位上运行这项操作。现在的处理器（包括 Intel 和 Sparc 处理器）使用的最通用的方法是实现名为比较并转换或 CAS 的原语。（在 Intel 处理器中，比较并交换通过指令的 cmpxchg 系列实现。PowerPC 处理器有一对名为“加载并保留”和“条件存储”的指令，它们实现相同的目地；MIPS 与

How to implement/use atomic counter in Metal fragment shader?

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问题 I want to implement an A-Buffer algorithm for order-independent-transparency in my Metal application. The description of the technique mentions using an atomic counter. I've never used one of these or even heard of them. I just read about atomic variables in the Metal Shading Language Specification, but I can't figure out how to actually implement or use one. Does anyone have experience with these in Metal? Can you point me to an example of how to set up and use a simple integer counter?

Object of class containing AtomicInteger's fails to be converted to JSON using GSON

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问题 I am trying to serialize an Object of Class (let's say MyClass) Here is roughly how MyClass.java looks like: public class MyClass { private static final AtomicInteger variableOne = new AtomicInteger(); private static final AtomicInteger variableTwo = new AtomicInteger(); private static final AtomicInteger variableThree = new AtomicInteger(); private static final AtomicInteger variableFour = new AtomicInteger(); /* * Have the getters and setters here */ } I am trying to convert object of the

Is Atomic Integer incrementAndGet() thread safe?

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问题 Is Atomic Integer incrementAndGet() method thread safe? I don't see any use of synchronized keyword in it. I am using following code to generate the unique id: public enum UniqueIdGenerator { INSTANCE; private AtomicLong instance = new AtomicLong(System.currentTimeMillis()); public long incrementAndGet() { return instance.incrementAndGet(); } } I am wandering if multiple threads that would call the method to generate unique ID would result in any issue? UniqueIdGenerator.INSTANCE

Removing negative values when variable is an atomic vector

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问题 I have a large dataset of a survey (originally a Stata(.dta) file). I would like to use the code below to convert negative values in my dataset to NA. If a variable has more than 99% NA's the code should drop it. #mixed data WVS <- data.frame(file) dat <- WVS[,sapply(df, function(x) {class(x)== "numeric" | class(x) == "integer"})] # NEGATIVES -> NA foo <- function(dat, p){ ind <- colSums(is.na(dat))/nrow(dat) dat[dat < 0] <- NA dat[, ind < p] } # process numeric part of the data separately ii

How to implement/use atomic counter in Metal fragment shader?

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I want to implement an A-Buffer algorithm for order-independent-transparency in my Metal application. The description of the technique mentions using an atomic counter. I've never used one of these or even heard of them. I just read about atomic variables in the Metal Shading Language Specification, but I can't figure out how to actually implement or use one. Does anyone have experience with these in Metal? Can you point me to an example of how to set up and use a simple integer counter? Basically each render pass I need to be able to increment an integer from within the fragment shader,

Java AtomicInteger的用法

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1.java.util.concurrent.atomic 的包里有AtomicBoolean, AtomicInteger,AtomicLong,AtomicLongArray, AtomicReference等原子类的类，主要用于在高并发环境下的高效程序处理,来帮助我们简化同步处理. 在Java语言中，++i和i++操作并不是线程安全的，在使用的时候，不可避免的会用到synchronized关键字。而AtomicInteger则通过一种线程安全的加减操作接口。 2.AtomicInteger的基本方法创建一个AtomicInteger AtomicInteger atomicInteger = new AtomicInteger(123); System.out.println(atomicInteger.get()); --->输出： 123 创建一个不传值的，默认值为0 AtomicInteger atomicInteger = new AtomicInteger(); System.out.println(atomicInteger.get()); ---->输出： 0 获取和赋值 atomicInteger.get(); //获取当前值 atomicInteger.set(999); //设置当前值 atomicInteger.compareAndSet