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== Background ==
== Background ==
[[Actor model|Active objects]] inherently support and automatically enforce the following best practices of concurrent programming<ref>{{Cite web
[[Actor model|Active objects]] inherently support and automatically enforce the following best practices of concurrent programming<ref>{{Cite web
| title = Prefer Using Active Objects Instead of Naked Threads
| title = Use Threads Correctly = Isolation + Asynchronous Messages
| author = Herb Sutter
| author = Herb Sutter
| url = http://www.drdobbs.com/parallel/prefer-using-active-objects-instead-of-n/225700095
| url = http://www.drdobbs.com/parallel/use-threads-correctly-isolation-asynch/2159004655
| date = June 14, 2010}}</ref>:
| date = March 16, 2009}}</ref>:


* Keep all of the [[Task (computing)|task]]'s data local, bound to the task itself and hidden from the rest of the system.
* Keep all of the [[Task (computing)|task]]'s data local, bound to the task itself and hidden from the rest of the system.

Revision as of 15:49, 12 January 2013

QP state machine frameworks
QP-framework
DeveloperQuantum Leaps
Written inQP/C and QP-nano in C, QP/C++ in C++
OS familyFramework / RTOS
Working stateMature
Source modelOpen source
Marketing targetEmbedded systems
Update methodCompany website
LicenseGPL and Commercial (Dual licensing)
Official websitestate-machine.com

QP (Quantum Platform) is a family of lightweight, open source software frameworks for building responsive and modular real-time embedded applications as systems of cooperating, event-driven active objects (actors).

Overview

The QP family consists of QP/C, QP/C++, and QP-nano frameworks, which are all strictly quality controlled, superbly documented[1], and commercially licensable.

All QP frameworks can run on "bare-metal" single-chip microcontrollers, completely replacing a traditional Real-Time Operating System (RTOS). Ports and ready-to-use examples are provided for all major CPU families. QP/C and QP/C++ can also work with a traditional operating system/RTOS, such as: POSIX (Linux, QNX), Windows, VxWorks, ThreadX, MicroC/OS, FreeRTOS, etc.

The behavior of active objects (actors) is specified in QP by means of hierarchical state machines (UML statecharts). The frameworks support manual coding of UML state machines in C or C++ as well as fully automatic code generation by means of the free graphical QM modeling tool[2].

The QP frameworks and the QM modeling tool are used in medical devices, defense & aerospace, robotics, consumer electronics, wired and wireless telecommunication, industrial automation, transportation, and many more.

Background

Active objects inherently support and automatically enforce the following best practices of concurrent programming[3]:

  • Keep all of the task's data local, bound to the task itself and hidden from the rest of the system.
  • Communicate among tasks asynchronously via intermediary event objects. Using asynchronous event posting keeps the tasks running truly independently without blocking on each other.
  • Tasks should spend their lifetime responding to incoming events, so their mainline should consist of an event loop.
  • Tasks should process events one at a time (to completion), thus avoiding any concurrency hazards within a task itself.

Active objects dramatically improve your ability to reason about the concurrent software. In contrast, using raw RTOS tasks directly is trouble for a number of reasons, particularly because raw tasks let you do anything and offer you no help or automation for the best practices[4]. As with all good patterns, active objects rise the level of abstraction above the naked threads and let you express your intent more directly thus improving your productivity.

Active objects cannot operate in a vacuum and require a software infrastructure (framework) that provides, at a minimum: an execution thread for each active object, queuing of events, and event-based timing services. In the resource-constrained embedded systems, the biggest concern has always been about scalability and efficiency of such frameworks, especially that the frameworks accompanying various modeling tools have traditionally been built on top of a conventional RTOS, which adds memory footprint and CPU overhead to the final solution.

The QP frameworks have been designed for efficiency and minimal footprint from the ground up and do not need an RTOS in the stand-alone configuration. In fact, when compared to conventional RTOSes, QP frameworks provide smaller footprint especially in RAM (data space), but also in ROM (code space). This is possible, because active objects don't need to block, so most blocking mechanisms (e.g., semaphores) of a conventional RTOS are not needed.

All these characteristics make [[event-driven active objects a perfect fit for single-chip microcontrollers (MCUs). Not only you get the productivity boost by working at a higher level of abstraction than raw RTOS tasks, but you get it at a lower resource utilization and better power efficiency, because event-driven systems use the CPU only when processing events and otherwise can put the chip in a low-power sleep mode.

QP Architecture and Components

QP consists of a universal UML-compliant event processor (QEP), a portable, event-driven, real-time framework (QF), a tiny run-to-completion kernel (QK), and software tracing system (QS).

QP components

QEP (Quantum Event Processor) is a universal UML-compliant event processor that enables direct coding of UML state machines (UML statecharts) in highly maintainable C or C++, in which every state machine element is mapped to code precisely, unambiguously, and exactly once (traceability). QEP fully supports hierarchical state nesting, which enables reusing behavior across many states instead of repeating the same actions and transitions over and over again.

QF (Quantum Framework) is a highly portable, event-driven, real-time application framework for concurrent execution of state machines specifically designed for real-time embedded systems.

QK (Quantum Kernel) is a tiny preemptive non-blocking run-to-completion kernel designed specifically for executing state machines in a run-to-completion (RTC) fashion.

QS (Quantum Spy) is a software tracing system that enables live monitoring of event-driven QP applications with minimal target system resources and without stopping or significantly slowing down the code.

Supported Processors

All types of QP frameworks (QP/C, QP/C++, and QP-nano) can be easily adapted to various microprocessor architectures and compilers. Adapting the QP software is called porting and all QP frameworks have been designed from ground up to make the porting easy.

Currently, bare-metal QP ports exist for the following processor architectures:

Supported Operating Systems

The QP/C and QP/C++ frameworks can also work with the traditional operating systems and RTOSes.

Currently, QP ports exist for the following OSes/RTOSes:

Licensing

All QP framework types are dual-licensed under the open source GPLv2 and a traditional, closed-source license. Users who want to distribute QP (e.g., embedded inside devices) can retain the proprietary status of their code for a fee. Several types of commercial, royalty-free, closed-source licenses are available.

See also

References

  1. ^ Samek, Miro (2008). Practical UML Statecharts in C/C++, Second Edition: Event-Driven Programming for Embedded Systems. Newnes. p. 728. ISBN 978-0-7506-8706-5.
  2. ^ "free graphical QM modeling tool".
  3. ^ Herb Sutter (March 16, 2009). "Use Threads Correctly = Isolation + Asynchronous Messages".
  4. ^ Herb Sutter (June 14, 2010). "Prefer Using Active Objects Instead of Naked Threads".
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