Tools and Benchmarks for Real-Time Systems

WATERS'17 • Re: Keynote by Reinhard von Hanxleden

2017-07-11T11:33:48+01:00

Thanks again to Reinhard von Hanxleden for the great keynote. The slides are now available

2017-06-27-Keynote-WATERS-rvh.pdf

Statistics: Posted by arne.hamann — Tue Jul 11, 2017

WATERS'17 • Re: Panel discussion: "Programming adaptive real-time systems"

2017-06-22T15:41:26+01:00

As the panel’s focus is on the “higher level languages […] for modeling adaptive real-time systems”, two interesting topics can be explored besides the ones mentioned in the pdf.

1. Finite State Machines are widely used (e.g., Simulink) in model-based design of embedded systems. Many works (especially [1,2]) have been devoted to their implementation on a target execution platform and verification of their timing correctness.

2. Logical Execution Time, brought up in this year’s industrial challenge, is a real-time programming abstraction introduced in Giotto. This programming language imposes two constraints on task execution: i) inputs are always read at the beginning of task period and outputs are always written at its end, ii) mode switch does not terminate execution of any task. More reactive models respecting the above mentioned constraints can be proposed [3,4].

[1] M. Di Natale and H. Zeng, "Task implementation of synchronous finite state machines," 2012 Design, Automation & Test in Europe Conference & Exhibition (DATE), Dresden, 2012, pp. 206-211.
[2] H. Zeng and M. Di Natale, "Schedulability Analysis of Periodic Tasks Implementing Synchronous Finite State Machines," 2012 24th Euromicro Conference on Real-Time Systems, Pisa, 2012, pp. 353-362.
[3] N. F. Martinek et W. Pohlmann. Mode Switching in GIA – An Ada Based Real-Time Framework. Department of Scientific Computing, University of Salzburg.
[4] T. Kloda, B. d’Ausbourg, and L. Santinelli, "Towards a more flexible timing definition language,” in 12th International Workshop Quantitative Aspects of Programming Languages and Systems at ETAPS 2014, 2014.

Statistics: Posted by tomasz.kloda — Thu Jun 22, 2017

WATERS'17 • Re: Panel discussion: "Programming adaptive real-time systems"

2017-06-21T13:04:02+01:00

At RealTime-at-work, we are developing such a language. It is called CPAL.
There are two use-cases for it. One is for timing-accurate simulation development, the second is for embedded dvpt (either by interpretation or code generation).
It is yet still immature in regards of our current discussion but the goal is to provide more and more supports. It is more high level than C.

It is really nice for timing accurate simulation for adaptive systems, and indeed harder for analysis.

Concerning @arne.hamann proposal, it looks very similar to computer graphic problem (ie frame timing). And usually it has impacts on the software architecture indeed.
Concerning @julien.forget proposal, parametric WCET is easily simulated within CPAL. Probably we should invest some time to demonstrate that by encoding some mälardalen benchmarks in CPAL...

Statistics: Posted by loic_fejoz — Wed Jun 21, 2017

WATERS'17 • Re: Panel discussion: "Programming adaptive real-time systems"

2017-06-20T12:53:54+01:00

This is tightly related to the underlying Operating System. In most OS, it shouldn't be too complicated to get the spent/remaining execution budget of a task (though there may not be a dedicated API function). Providing language primitives to interrogate the OS on these aspects shouldn't be too hard either.

I think that the challenge here would rather be to introduce these primitives in a way such that the program can still be analyzed for schedulability. Assume for instance a program where some task A is replaced by some task A' if we realize at some point that there is not enough execution budget for A. Implicitely, this assumes that there is enough budget for A' in any case, so that either there is enough budget for A to execute and meet its deadline or instead A' executes and meet its deadline. If the condition for switching from A to A' is a mere Boolean expression, it can be quite difficult for an automated program analysis to infer this information (the pair A/A' always meets its deadline). Primitives must be built in a way such that the program clearly exhibits the fact that A never executes for more than a predefined budget.

On a related note, we proposed an alternative to scheduling introspection, which instead relies on parametric WCET analysis (https://hal.archives-ouvertes.fr/hal-01239158/). Instead of computing a constant WCET value, our proposed analysis produces a formula that depends on some dynamic parameters (e.g. cache state, input value, etc.). During execution, at job release, we can instantiate the formula (since parameter values are known at that point), check whether the obtained WCET is over some acceptable threshold and modify the program behavior accordingly, e.g. to replace A by A'. The advantage here is that A does not consume any budget at all if its WCET is too high, it is immediately replaced by A'.

Statistics: Posted by julien.forget — Tue Jun 20, 2017

WATERS'17 • Re: Panel discussion: "Programming adaptive real-time systems"

2017-06-19T09:25:46+01:00

One interesting point from my side would be the following:

For some kind of functionalities it might be of great use to "introspect" what is going on on scheduling level. For instance, in model predictive control or when using so-called anytime algorithms, one might want to decide dynamically if another iteration of the algorithm (leading to better functional performance) can be performed.

Do you think there might be a sensible way to provide high-level programming primitives to enable such reasoning?

Statistics: Posted by arne.hamann — Mon Jun 19, 2017

WATERS'17 • Re: Keynote by Reinhard von Hanxleden

2017-06-19T09:15:40+01:00

I would like to discuss the following topics at WATERS:

- Would it make sense to include a physical notion of time in synchronous languages for real-time applications (e.g. to represent deadlines)? How could that be realized and what would be the semantics?
- How can synchronous programs be executed truly parallel on multi-core platforms?
- Are modern programming paradigms (e.g. OO) amenable to synchronous languages?

We at Bosch are also concerned with practical issues for realizing large systems with sync. languages: separate compilation of modules with causality analysis, compound data structures, etc.

Anymore questions / opinions concerning sync. languages?

Statistics: Posted by arne.hamann — Mon Jun 19, 2017

WATERS'17 • The 2018 industrial challenge

2017-06-09T13:18:03+01:00

About the WATERS industrial challenge
The purpose of the WATERS industrial challenge is to share ideas, experiences and solutions to a concrete timing verification problem issued from real industrial case studies. It also aims at promoting discussions, closer interactions, cross fertilization of ideas and synergies across the breadth of the real-time research community, as well as attracting industrial practitioners from different domains having a specific interest in timing verification.

The 2018 industrial challenge
We are glad to announce that the 2018 challenge will be proposed by Emmanuel Ledinot from Dassault Aviation. An initial presentation of the challenge is given below.

The WATERS 2018 industrial challenge is entitled " Certifiable contract-based timing analysis of CPS" and based on a public domain use case under development ( https://github.com/AdaCore/RESSAC_Use_Case/). This use case, managed by the RESSAC project at IRT St Exupery (Toulouse, France) led by Airbus, was designed as an open research lab. to explore reformation of aeronautic certification. Such a reformation was initiated by the Federal Aviation Administration in the US by fall of 2015, and supported by world aeronautic industry. The use case is based on a small drone-like Cyber Physical System: hybrid multi-system mixing simple mechanics, hydraulics, electrical powering, flight control, mission management, fault tolerance, and distributed real-time computation. The use case is focused on model-based and contract-based refinement of hybrid systems, because they are anticipated as key enablers for future design assurance, in addition to model-based and contract-based software/hardware development. On the academic side, an attempt to carry out an end-to-end formal safety case has started and is intended to be a long term research challenge for the hybrid system community.

The WATERS 2018 challenge is a call for proposals to contribute the concepts, models, candidate technologies, and analyses of the RESSAC use case's middleware layer (named increment 4 in the documentation). 'Middleware layer' is an umbrella term to denote all the features related to the executive layers (RTOS, task scheduling, message scheduling), communication protocols (internal to the drone and with the ground station), and hard-real time timing analysis. Each team participating to the 2018 challenge is invited design the middleware layer, chose technological solutions, and then play the role of an applicant substantiating the correctness of its design to an Authority. Contributions are expected on timing-contract languages, suitable abstractions of the concrete technological solutions, compositionality and genericity of the correctness arguments.

Statistics: Posted by Sophie Quinton — Fri Jun 09, 2017