It is a segmented, immobile, frozen space. Only the intendants, syndics and guards will move about the streets and also, between the infected houses, from one corpse to another, the “crows”, who can be left to die: these are “people of little substance who carry the sick, bury the dead, clean and do many vile and abject offices”. If it is absolutely necessary to leave the house, it will be done in turn, avoiding any meeting. Each family will have made its own provisions but, for bread and wine, small wooden canals are set up between the street and the interior of the houses, thus allowing each person to receive his ration without communicating with the suppliers and other residents meat, fish and herbs will be hoisted up into the houses with pulleys and baskets. The syndic himself comes to lock the door of each house from the outside he takes the key with him and hands it over to the intendant of the quarter the intendant keeps it until the end of the quarantine. On the appointed day, everyone is ordered to stay indoors: it is forbidden to leave on pain of death.
Each street is placed under the authority of a syndic, who keeps it under surveillance if he leaves the street, he will be condemned to death. The following, according to an order published at the end of the seventeenth century, were the measures to be taken when the plague appeared in a town.įirst, a strict spatial partitioning: the closing of the town and its outlying districts, a prohibition to leave the town on pain of death, the killing of all stray animals the division of the town into distinct quarters, each governed by an intendant. (in collaboration with the Journal “Antinomie”, ) The Birth of the Prison”, translated by A. singletonAcquireRelease.cpp #include #include #include #include #include Īuto total= fut1.get() + fut2.get() + fut3.get() + fut4.From “Discipline and Punish. Because I didn't specify the C++ memory model the default applies: Sequential consistency. I base my implementation on the well-known double-checked locking pattern. With atomic variables, my job becomes extremely challenging. How fast is the classical thread-safe implementation of the singleton pattern? Without optimization Return std::chrono::system_clock::now() - begin Īuto fut1= std::async(std::launch::async,getTime) Īuto fut2= std::async(std::launch::async,getTime) Īuto fut3= std::async(std::launch::async,getTime) Īuto fut4= std::async(std::launch::async,getTime) Īuto total= fut1.get() + fut2.get() + fut3.get() + fut4.get() MySingleton* MySingleton::instance= nullptr Īuto begin= std::chrono::system_clock::now() MySingleton& operator=( const MySingleton&)= delete MySingleton( const MySingleton&)= delete singletonSingleThreaded.cpp #include #include The command line gives you the details of the compiler Here are the gcc and the cl.exe.Īt first, the single-threaded case. What's the difference between the optimized and non-optimized versions?įinally, I collect all numbers in a table.Is there a significant difference between Linux (gcc) and Windwos (cl.exe)?.How is the relative performance of the different singleton implementations?.If not the compiler will optimize away my access to the singleton and my program becomes too fast. For the translation of the program with maximum optimization, I have to use a volatile variable in the static method getInstance. I compile the program with maximum and without optimization.
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My Linux PC has four, my Windows PC has two cores. Here I'm only interested in the performance. In contrast, the access from the multithreading program will be done by 4 threads. The first access will initialize the object.
I use as a reference point for my performance measurement a singleton object which I sequential access 40 million times. From a birds-eye, you can have guarantees from the C++ runtime, locks or atomics. I'm totally curious about the performance implications. There are a lot of different ways to initialize a singleton in C++11 in a thread-safe way. You get the performance numbers and can reason about your uses cases for the thread-safe initialization of a variable. So in this post, I discuss different ways to initialize a singleton in a multithreading environment. From that point on you can use it without synchronization. But the singleton pattern is an ideal use case for a variable, which has only to be initialized in a thread-safe way. There are a lot of issues with the singleton pattern.