lifelock guarantee

= true; //Statement 4 From the code order, the above four statements should be executed sequentially, but in fact the JVM actually executes this code without guaranteeing that they will be executed exactly in this order.In order to improve the overall execution efficiency of the program, it is possible to optimize the code by adjusting the code order and executing the code in a more efficient order.In this case, someone is going to have to worry--what, the CPU doesn't execute code i

is the 1,volatile keyword guaranteed to be thread safe? （）Answer: NoThe volatile keyword is used in multi-threaded synchronization to guarantee read visibility, and the JVM simply guarantees that the value that is loaded from main memory to the working memory of the thread is the most recent read value, not the cache. However, multiple threads write to volatile, which is not guaranteed to be thread safe.If thread 1, thread 2 in the read,load operation

between multiprocessor is high or the memory address of the instruction access is not aligned. Disables this instruction from reordering read and write instructions before and after. Flushes all data in the write buffer to memory. Note knowledge: There are 3 types of locks on CPUs: 3.1 Processor automatically guarantees the atomicity of basic memory operations First, the processor automatically guarantees the atomic nature of the basic memory operation. The processor guarantees that reading or

reading or writing a byte from the system memory is atomic, meaning that when a processor reads a byte, the other processor cannot access the byte's memory address. Pentium 6 and the latest processors can automatically guarantee that a single processor is atomic to the 16/32/64 bit in the same cache line, but a complex memory processor does not automatically guarantee its atomicity, such as cross bus width

in order, then it is possible to print 0 instead of 42. (because the initial value of number is 0).Therefore, reordering is a possible cause of thread safety problems. If a variable is declared volatile, then the variable is not reordered, that is, the virtual opportunity guarantees that the code before the variable will be executed before it, and then the code will be slower than it executes.For example, if the number above is declared volatile, then number = 421 will be executed first rather

, but in fact the JVM actually executes this code without guaranteeing that they will be executed exactly in this order.In order to improve the overall execution efficiency of the program, it is possible to optimize the code by adjusting the code order and executing the code in a more efficient order.In this case, someone is going to have to worry--what, the CPU doesn't execute code in my Code order, how do we make sure we get the results we want? In fact, you can rest assured that the CPU is no

thrown. If the function is successful, it is completely successful. Otherwise, the program will return to the status before the function is called. Do not throw (nothrow) guarantee: Promise never throw an exception because they can always complete the functions they previously promised. All operations acting on built-in types (such as ints and pointers) provide the nothrow guarantee. The function with "Bl

before writing the volatile variable).Thread A writes a volatile variable, and then thread B reads the volatile variable, which essentially is thread a sending a message to thread B through main memory. Does 5.volatile guarantee atomic sex? Knowing from above that the volatile keyword guarantees the visibility of the operation, but does volatile guarantee that the operation of the variable is atomic? Le

Java Multithreading-----------------volatile memory semantics　　The volatile keyword is the most lightweight synchronization mechanism provided by a Java virtual machine. Because the volatile keyword is related to the Java memory model, we have added more additions to the Java memory model before introducing the volatile keyword (as described in the previous blog post).1. Java memory model (JMM)JMM is a specification, mainly used to define the access rules for shared variables, in order to solve

code that calls it does not have the exception security, so it is writtenIs there any point in the exception security code?#3.” Strong assurance that "often can be achieved by Copy-and-swap."An example with Copy-and-swap: struct pmimpl{ //pmimpl = prettymenu Impl std::tr1::shared_ptr(1)Because strong guarantees such as copy-and-swap tend to consume more time and space, in order toTo ensure better efficiency, it should be replaced with "basic guar