This protocol has been enormously simplified in the task_group environment. This is what we will be doing in Chapter 16, when discussing the low-level scheduler API based on the task class. The specific derived task class must be defined, and objects instances of this class must be constructed and submitted for execution to the scheduler. Tasks are in general defined in TBB as instances of a class derived from the basic task class, in which the execute() virtual function is defined. 11.10.1 Defining Tasks in the task_group Environment This section shows how this happens in detail, on the basis of the same examples already proposed in the OpenMP chapter. It is important to keep in mind that this member function waits for all descendants, not just direct children. The task_group class has two basic member functions: the run() member function that allocates and spawns a task, and the wait() member function that waits for the termination of all tasks previously spawned by the task_group object. It also implements a task group cancellation utility, very much like the one discussed in the OpenMP environment. It implements the two basic synchronization patterns discussed for OpenMP tasks: waiting for direct children and waiting for all descendants. This class can be used to run a group of tasks-which can be dynamically enlarged with new tasks once running-as a single, encapsulated parallel job. The official documentation is in the “Task Group” link of the Reference Guide. TBB has recently introduced the task_group class that implements an elegant and easy-to-use programming interface to the task scheduler. Victor Alessandrini, in Shared Memory Application Programming, 2016 11.10 High-Level Scheduler Programming Interface I will cover how to write your own constructors and operators in the C++ usage chapter later in this book. These can then perform a deep copy of your object, that is, create a copy of the Impl object instead of just copying the pointer. If you do want your users to be able to copy your pimpled objects, then you should declare and define your own copy constructor and assignment operator. Also, the new C++11 specification lets you disable these default functions completely (see Chapter 6 for details). Alternatively, if you are using the Boost libraries, then you could also simply inherit from boost::noncopyable. Declaring these as private is also a good idea so that attempts to copy an object will generate a compile error rather than a link error. You don't have to provide implementations for these just the declarations are sufficient to prevent the compiler from generating its own default versions. You can do this by explicitly declaring a copy constructor and assignment operator. If you don't intend for your users to create copies of an object, then you can declare the object to be non-copyable. Two options for dealing with this are as follows. However, both objects will attempt to delete this same Impl object in their destructors, which will most likely lead to a crash. This is bad for pimpled classes because it means that if a client copies your object then both objects will point to the same implementation object, Impl. However, these compiler-generated constructors will only perform a shallow copy of your object. It is also possible to explicitly call the constructors and pass arguments to be the property values this is necessary if the superclass constructors require that input arguments be passed.Ī C++ compiler will create a copy constructor and assignment operator for your class if you don't explicitly define them. MATLAB automatically makes implicit calls to the superclass constructors using no arguments when the class is defined as a subclass in the class definition line. If the class being defined is a subclass, the constructor function of the superclass must be called to initialize its properties. Overloading the set.PropertyName functions for all properties allows for even more control over all functions that set the properties, including the constructor function. To be truly general, the types of the input arguments should also be checked to make sure that they are the correct types for the properties. Constructor functions should be general and should allow for the case in which no input arguments are passed by creating default property values. Constructor functions always have the same name as the class and return only the initialized object this is true for both value and handle classes. If a class definition does not include a constructor, MATLAB will initialize the properties to either default values provided in the property definition block, or to empty vectors. Stormy Attaway, in MATLAB (Fifth Edition), 2019 11.3.5.1 Constructor FunctionsĪs we have seen, all classes should have constructor functions, which initialize the properties in an object.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |