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Multithreading in LabVIEW
Published in Rick Bitter, Taqi Mohiuddin, Matt Nawrocki, LabVIEW™ Advanced Programming Techniques, 2017
Rick Bitter, Taqi Mohiuddin, Matt Nawrocki
Priority and scheduling are different for Pthreads; Pthreads have defined scheduling policies: round robin; first-in, first-out; and others. The FIFO policy lets a thread execute until it completes its execution or becomes blocked. This policy is multitasking by any other name, because there is no preemption involved. The round-robin policy is preemptive multithreading. Each thread is allowed to execute for a maximum amount of time, a unit referred to as a “quantum.” The time of a quantum is defined by the vendor’s implementation. The “other” policy has no formal definition in the POSIX standard. This is an option left up to individual vendors. Pthreads expand on a concept used in UNIX called “forking.” A UNIX process may duplicate itself using a fork command. Many UNIX daemons such as Telnet use forking. Forking is not available to the Win32 programmer. A process that generates the fork is called the Parent process, while the process that is created as a result of the fork command is referred to as the Child process. The Child process is used to handle a specific task, and the Parent process typically does nothing but wait for another job request to arrive. This type of multitasking has been used for years in UNIX systems.
A product-process-resource based formal modelling framework for customized manufacturing in cyber-physical production systems
Published in International Journal of Computer Integrated Manufacturing, 2022
Ge Wang, Di Li, Yuqing Tu, Chunhua Zhang, Fang Li, Shiyong Wang
In the FD, products represent substances that have market demand, as well as intermediate forms in the production process and raw material purchasing. Products refer not only to product types, but can also represent individual artefacts (Pfrommer, Schleipen, and Beyerer 2013). Processes are associated with a set of attributes that are used to describe a single process realization of a product and the demand for it, and refer to manufacturing, logistics, or other production-related processes, such as information exchange and reprocessing. The process can form a hierarchical structure; for instance, a parent process contains child processes, and a child process is a subset of the parent process. Resources are entities involved in process execution, which can be individual machines, such as packaging devices, or specific machines bundled together, such as robots with fixtures, or a combination of them (Jarvenpaa, Siltala, and Lanz 2016). Moreover, resources can also mean providing equipment for a certain process.