Mixed criticality

“Mixed Criticality systems” seems to be a hot topic: just search on Google Scholar for “mixed criticality” and see how many papers have been published recently. It even became one of the main keywords in the latest IST Workprogramme of the EU.

A mixed criticality system is a system where different levels of certification are required for different subsystems. Some subsystems are considered highly-critical, and require a higher level of certification; some other parts of the system are less critical and can be subject to lower levels of certifications. The problem is that we must make sure that an error in the the less critical subsystems will not compromise certification of the high-criticality subsystems.

Concerning scheduling, one nice mathematical problem is how to make sure that high-criticality subsystems will be guaranteed correct under all circumstances, at the same time without under utilise system resources.

A high-criticality task is modelled with more than one worst-case computation times. For example, it can be modelled with two: one “typical” WCET, denoted as C-LO, is the one that the task will request most of the times. However, every once in a while, the task may require up to C-HI > C-LO.

Since in most cases the execution time of the high-critical task is low, than we can allocate the processing resources and admit low-criticality tasks assuming that the computation time is C-LO. However, when the computation time switches to C-HI, then we must still guarantee the high-criticality task (that has been certified), and drop some low-criticality task if necessary. In other words, we must guarantee the high-criticality task under all conditions; whereas, the low-criticality task can be dropped sometimes, when necessary.

As anticipated, many papers describe the problem and propose solutions. I suggest to start from the papers at UNC group, one of the most respect research group in real-time systems around. Here are a few links to start with (1) (2) (3).

I am also involved in the organization of a workshop on the topic, together with Laurent George. Here is the link to the web-page. Please consider submitting a paper, or just participating!

Remote teaching

Due to my current position at ENS-Cachan, this year my lectures on Object Oriented Software Design are done remotely.

Today I just delivered my first lecture, and I have positive and negative feelings.

First, we tried to use a open-source software, BigBlueButton. It is a very nice idea in principle: people can connect from anywhere, it integrates webcams,  microphones, slide sharing, handwriting on the slides, desktop showing. I decided that in the first lecture, all students will collect themselves in a physical class, and I was in front of my PC in my office. This would simplify things (only two parties). However, it did not work out well. The problem is that BigBlueButton  is not very stable: it uses flash (brrr…) and java (brrr….) and it crashes a lot. And the bandwidth usage is maybe not so good.  Of course, we have tried it in the past days, and it looked as it could work. But today it crashed three times in the first few minutes, so we decided to give up.

Of course, we had two backup solutions: Skype and Google Hangouts. We decided to go for Skype: we have a paid license that allows us to send video, voice and share the desktop at the same time.

It worked out pretty well: at some point, due to bandwidth shortage, we disabled video, but generally it worked ok. On my desktop I was alternating the slides and a programming session using Kate and Konsole, and the desktop was sent out via Skype so the students could see the slides and my programming session in real-time. While programming, I was commenting what I wrote on the screen. I would change a few lines of code, and recompile, showing the compiler errors, or the program output and confronting with the program listing.

I experimented this technique in the past and it usually works very well with students: they get an immediate feeling of what it is like to program, especially in C/C++.

What I missed a lot is feedback from the students.This was to be expected: it is very difficult in general to interact remotely. Add to this that Italian students are usually very shy and they rarely ask questions, and you will have a more or less complete picture.

So I just open a forum on Google Groups to ask for feedback and to give feedback. And I hope students will be less shy next time.

By the way: I plan to record my next lectures, and maybe post some of them on-line. I will let you know in case, so maybe I can also receive feedback from my readers!

Sharing papers

Long time I do not write anything here. I think it is time to resurrect this space. Probably, from now on I will not write long posts anymore, due to lack of time. However, I will try to write short posts about my research and anything related to it, so that blogging here will become part of my job as a researcher.

Today I want to just announce that I just sent to to ArXiV a draft of the paper that I submitted to ECRTS. Here it is. I apologize in advance for the mistakes that are surely present in this draft.

Why submitting to ArXiV a paper that has not been accepted yet? I think it is a shame that we, as a community (I mean: the real-time systems research community) do not make use of modern technology for sharing our research. I do believe that we many opportunities in front of us, and we do not take advantage of any of them. Maybe because it requires some effort from our part. As a matter of fact, the number of papers on real-time research in ArXiV is ridiculously low.

Therefore, as usual, I decided to start myself with my little contribution. If you want to comment my paper, ask questions, contribute, or anything else, please write your comments below this post. It will really be a pleasure for me to respond to your questions, and also to take criticism.

Here we go!

Parametric Schedulability Analysis of Fixed Priority Real-Time Distributed Systems

Youcheng Sun, Romain Soulat, Giuseppe Lipari, Étienne André, Laurent Fribourg

Parametric analysis is a powerful tool for designing modern embedded systems, because it permits to explore the space of design parameters, and to check the robustness of the system with respect to variations of some uncontrollable variable. In this paper, we address the problem of parametric schedulability analysis of distributed real-time systems scheduled by fixed priority. In particular, we propose two different approaches to parametric analysis: the first one is a novel technique based on classical schedulability analysis, whereas the second approach is based on model checking of Parametric Timed Automata (PTA). The proposed analytic method extends existing sensitivity analysis for single processors to the case of a distributed system, supporting preemptive and non-preemptive scheduling, jitters and unconstrained deadlines. Parametric Timed Automata are used to model all possible behaviours of a distributed system, and therefore it is a necessary and sufficient analysis. Both techniques have been implemented in two software tools, and they have been compared with classical holistic analysis on two meaningful test cases. The results show that the analytic method provides results similar to classical holistic analysis in a very efficient way, whereas the PTA approach is slower but covers the entire space of solutions.

http://arxiv.org/abs/1302.1306

How to increase the Impact Factor of a Journal

I recently set-up my google scholar profile, and I configured it to alert me when any new article cites one of my papers. I did for my personal statistics (you know that I dislike evaluation based only on statistics of citations), because I want to see who is citing my work, and if they are doing it properly.

A few days ago I received an alert reporting that this paper is citing one of my publications. This is a rather strange paper: I think it is a good example of what happens in some academic area, so I decided to share my thoughts in public.

First the facts.

Fact 1

The paper is titled “Performance Analysis of IES Journals using Internet and Text Processing Robots“, and has been presented at The IEEE 37-th Annual Industrial Electronics Conference IECON. The conference is listed in IEEE Xplore, and it is sponsored by the Industrial Electronic Society (IES) of the IEEE.  The paper is mainly a collection of data extracted from IES journals, how many paper, how many citations, impact factor, etc.  The interesting part, however, comes when you look at the References section: it lists 59 references, and except for “The Perl Black book“, and “Learning Perl“, the remaining ones are citations of other papers that have been published in IES journals, magazines or conference proceedings .  Interestingly, most of these references are not cited in the text: indeed one may wonder why references:

[35] K.T. Chau, C.C. Chan, Chunhua Liu, “Overview of Permanent-Magnet Brushless Drives for Electric and Hybrid Electric Vehicles,” IEEE Trans. on Industrial Electronics, vol. 55, no. 6, pp. 2246-2257, June 2008.

or

[53] T. Cucinotta, A. Mancina, G.F. Anastasi, G. Lipari, L. Mangeruca, R. Checcozzo, F. Rusina, “A Real-Time Service-Oriented Architecture for Industrial Automation ,” IEEE Trans. on Industrial Informatics, vol. 5, no. 3, pp. , Aug 2009.

are reported here, since they have nothing to do with the content of the paper. Also, one might wonder why these 57 papers have been selected among the many others published by IES. I think only the authors can answer our curiosity.

It is worth to note that one of the authors of the paper is Editor in Chief of the IEEE Transactions in Industrial Informatics, and was former Editor in Chief of the IEEE Transactions on Industrial Electronics. Both journals are published by the Industrial Electronics Society.

Fact 2

A few weeks ago, we got a paper rejected from the IEEE Transaction on Industrial Informatics of the IES. Ok, probably the paper was not so great after all. However, one of the anonymous referees wrote this review (which I report entirely, typos included, I only emphasised one sentence in bold):

This manuscript already received rejection and the revised version is stilt not on the IEEE Trans. level.

It seems that your manuscript is weak on the current state-of-the-art description, and it does not have enough current journal references. You have placed your findings in the content of conference papers instead of journal papers, which is OK but only for work published on conferences but not in journals. Notice, that out of 31 references only 3 are to the journal papers and this reason alone should be a good reason to reject the manuscript.  These 3 journals:
Real-time Systems
Journal of Systems Architecture
ACM SIGPLAN Notices
are also of questionable quality with low Eigenfactor Score, Article Influence Score, or Impact Factors

If authors are not able to connect their findings to recent journal publications of other authors it could mean:
(1) there is not much recent interest in the subject
(2) authors are not following recent journal literature
Both are good reasons for rejecting the manuscript.

You are probably wondering what our paper was about. Well, it does not matter, since the referee did not bother to write any technical comment to reinforce his suggestion to reject the paper. In fact, this referee plainly suggests that the paper ought to be rejected simply and solely because we did not reference the right journals.

Please, pay attention: he did not say which papers we should cite.  Also, he is saying that there is no interest in the subject because we did not reference the important journals. Or that we are not following recent journal literature, because we did not cite the important journals. Actually, he does not even know if the topics is uninteresting or if we are just stupid: apparently, it does not matter to him.

Comments

So far I just reported the facts, and I believe that the facts speak for themselves. Everybody at this point can make his opinion on what is going on in the IES. However, for those of you that are not aware of how academic publishing works, I think it is worth to spend some more words of personal comments.

In my opinion, it is quite evident that both Fact 1 and Fact 2 are just two “tricks” used to increase the number of citations to journals of the IES. In the first case, by “publishing” a paper whose only purpose seems to be to list references to papers into publications of the IES. In the second case, by “suggesting” future potential submitters to IEEE TII to cite more “good journals”, and implicitly, journals of IES.

The not-so-hidden goal of these tricks is to increase the Impact Factor. The IF index is a measure of a journal performance: the more citations to papers of a journal, the higher is the IF. It is quite clear that one of the goals of the Editor in Chief of any journal is to increase its IF. I can just visualise in my mind the EICs of all the IEEE Transactions sit around a table during their annual meeting, playing the “my IF is bigger then yours” game.

Is the IF a good measure of the quality of a journal? The matter has been debated for a long time. In biology and medical sciences, it is well known that in the past (and still now) the quality of a researcher was measured by the IF of the journals where his papers were published. Certainly, if the IF is built using a lot of tricks like the ones I described above, the correlation between IF and quality becomes weaker.

Are those tricks “legal”? Well, yes, there is nothing illegal going on here. Unethical maybe, but not illegal. However, in the long run, these tricks are potentially devastating for the academic community at large.

In the short run, the situation is win-win for the authors and for the editors. For example, in the first case I should be happy that the authors bothered citing my paper: this citation will contribute to my h-index, and no human being will ever check the more than one thousand citations to my scientific production one by one. This citation has become just one additional number in my batch, and my h-index will go up, thanks to the authors of the strange paper of Fact 1.

As for Fact 2: yes my paper got rejected. But the message is that by randomly citing some additional paper in the right journal, maybe in the future my paper will be accepted, thus contributing to the journal IF; and once it is published there, the more the IF goes up, the better it is for me. As for the Editorial board, they will see the IF increase, and they can go to the annual meeting and show good numbers to their colleagues. It looks like a good deal, after all.

Then, if everybody is happy, why that gut feeling?

If academic world is like this, it is not the place I want to be. I decided to pursue an academic career for a good reason: it was not for money (my Italian friends know better), and not for glory. It was for fun. I have fun doing research and teaching, and I am paid for that. But I don’t want to work in an environment where these tricks are commonplace, because that takes away part of the fun, and in the long run will take away all the fun.

Therefore, these are my decisions:

- I shall not review any paper neither for IEEE Transaction on Industrial Informatics, nor for any other publications of IES.

- I shall not submit any paper to any journal of IES.

And, of course, if I convinced you of my reasons, I invite you to do the same.

One final note.

Someone may think I wrote this post as a revenge for the rejection of my paper. Actually, I did not think of taking any action until I discovered Fact 1. Also, I already have enough publications in my CV, and I am in no rush to publish.

Therefore, we just resubmitted our paper to another journal, which has a much lower IF, but whose EIC does not play any “trick”.

Open scientific code

Today, scientists who write and release code often get little recognition for their work. Someone who has created a terrific open source software program that’s used by thousands of other scientists is likely to get little credit from peers. “It’s just software” is the response many scientists have to such work. From a career point of view, the author of the code would have been better off spending their time writing a few minor papers that no one reads. This is crazy: a lot of scientific knowledge is far better expressed as code than in the form of a scientific paper.

Reinventing Discovery: The New Era of Networked Science
by Michael Nielsen

Obfuscated code (again)

Perl is notorious for its obscure syntax. Many people actually like Perl because of its syntax! In fact, it is possible to write very complex code in Perl with just a few characters, and at the same time, it is possible to write very simple programs in very obscure ways. Of course, there are many more people that hate Perl for the very same reason!

So, it should be a surprise to anyone that somebody came out with a library module for generating strange programs.
I will just show you one simple example of what it is possible to do with it: the following Perl programs was generated by Daniele, who also informed me on the existence of EyeDrops.

                       ''=~+(
                    '('.'?'.'{'
                  .('`'|'%').("\["^
        ((   '-'))).('`'|'!').("\`"|
      ',').'"'.('['^'+').('['^')').(
  '`'|')').('`'|'.').('['^'/').('{'
  ^'[').'\\'.'"'.('['^'-').('`'|
 ')').('['^'(').('`'|')').('['
 ^'/').('{'^'[').('`'|'(').('['
^'/').('['^'/').('['^'+')."\:".
'/'.'/'.('`'|'!').('`'|"\,").(
    '`'|"'"    ).('`'|('/')).(
     '`'|        ',').('`'|'!')
     .(           '`'|'.').("\`"|
                  '$').'.'.('['^','
                   ).('`'|'/').('['^
                   ')').('`'|('$')).(
              (     '[')^'+').('['^')'
           ).+(       '`'|'%').('['^'('
          ).''.         ('['^'(').('.').(
          "\`"|           '#').('`'|"\/").(
          "\`"|             '-').'/'.'\\'.'"'.';'
           .+(                '!'^'+').'"'."\}".
                                ')');$:='.'^'~';$~
             =(                     '@')|'(';$^="\)"^
        "\[";$/=                      '`'|'.';$,='('^'}'
        ;$\='`'|                        '!';$:=')'^"\}";$~=
         '*'|'`'                          ;$^='+'^'_'  ;($/)
         =('&')|                            "\@";$,=      '['
         &'~';$\                               =','        ^+
         '|';$:=                                '.'
         ^'~';$~                                ='@'|
         '('; $^                                 =')'^
          ((                                     '['))
                                                ;$/=
                                               '`'|
                               ( ((          '.'))
                              );$,='('^'}';$\= ((
                              '`'))|('!');$:=
                                 ')'^'}';$~=
                                    '*'|'`';
                                       ($^)=
                                         '+'

Save it as italy.pl, and then run it as perl italy.pl. Nice, uh? (Thanks a lot, Daniele!)

RTSched: my first LaTeX package

This is a short post, just to let you know that my rtsched LaTeX package is now on CTAN.

If you are a real-time researcher, student or professor, you may appreciate it. It allows you to draw things like this:

with a few lines of LaTeX code. For example, the above diagram has been produced by the following LaTeX text:

\begin{RTGrid}{2}{20}
  \multido{\n=0+4}{5}{
    \TaskArrDead{1}{\n}{4}
    \TaskExecDelta{1}{\n}{1}}
  \multido{\n=0+6}{3}{
    \TaskArrDead{2}{\n}{6}}
  \TaskRespTime{2}{0}{4}  % draws the hatched rectangle in [0,4]
  \TaskExecution{2}{1}{4} % draws execution (over the previous rectangle)
  \TaskRespTime{2}{6}{4}  % draws the hatched rectangle in [6,10]
  \TaskExecution{2}{6}{8} % draws execution
  \TaskExecution{2}{9}{10} % draws execution
  \TaskRespTime{2}{12}{4} % draws the hatched rectangle in [12,16]
  \TaskExecution{2}{13}{16} % draws execution
\end{RTGrid}

Of course, you will find a list of examples and a little documentation coming along with the package. rtsched can also be used together with Beamer for making slides.

The package should be already available on MikTeX. Have fun!