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| \title{\bf PP \emph{Compilation Techniques for Robust Embedded Systems}} |
\title{\bf PP \emph{Compilation Techniques for Robust Embedded Systems}} |
| |
|
| \author{{\sc Ulrich Schmid}\\ |
\author{{\sc Jens Knoop and Andreas Krall}\\ |
| s@ecs.tuwien.ac.at |
\{knoop,andi\}@complang.tuwien.ac.at |
| } |
} |
| |
|
| \bibliographystyle{unsrt} |
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| \begin{document} |
\begin{document} |
| \maketitle |
\maketitle |
| |
|
| PP leader: \emph{Jens Knoop and Andreas Krall} |
PP leader: \emph{Jens Knoop and Andreas Krall (beide E185.1)} |
| |
|
| Associated researchers: \emph{} |
|
| |
|
| |
|
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Associated researchers: \emph{Anton Ertl (E185.1), Bernhard Gramlich (E185.2),}\\ |
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\phantom{Associated researchers: } \ \ \ \ \emph{Franz Puntigam (E185.1)} |
| |
|
| \subsubsection*{Motivation:} |
\subsubsection*{Motivation:} |
| %\emph{Informal description of the purpose of the PP (3-5 lines)} |
%\emph{Informal description of the purpose of the PP (3-5 lines)} |
| Every embedded system consists of software which is written in a high |
Every embedded system consists of software which is written in a high |
| level language, compiled to machine language and executed on a |
level language, compiled to machine language and executed on a |
| processor. For robust embedded systems new verified compilation |
processor. For robust embedded systems new verified analysis and |
| techniques are necessary to optimize for performance, power, space, |
compilation, simulation, and specification methods are necessary to |
| concurrency and reliability. |
support the programmer during application development and maintenance |
| |
and to optimize for performance, power, space, concurrency and |
| |
reliability during compilation. |
| |
%for short, new programming and |
| |
%compilation techniques for robust embedded systems development and |
| |
%deployment. |
| |
|
| \subsubsection*{State of the art and related work:} |
\subsubsection*{State of the art and related work:} |
| %\emph{Briefly describe the scientific state of the art (20-30 lines)} |
%\emph{Briefly describe the scientific state of the art (20-30 lines)} |
| |
|
| %Compilation Techniques for Reliability |
%Compilation Techniques for Reliability |
| |
|
| Because of the exponential increase of the number of transistors and |
Because of the exponential increase of the number of transistors and |
| the continuing decrease of the feature sizes of current processors |
the continuing decrease of the feature sizes of current processors |
| soft errors mainly caused by energetic particles are becoming an |
\emph{soft errors} mainly caused by energetic particles are becoming an |
| important design issue for robust embedded systems. Blome et |
important design issue for robust embedded systems. Blome et |
| al.~\cite{Blome+06} observed that a majority of faults that affect the |
al.~\cite{Blome+06} observed that a majority of faults that affect the |
| architectural state of a processor come from the register file. Lee |
architectural state of a processor come from the register file. Lee |
| and Shrivastava and proposed different solutions to cope with this |
and Shrivastava \cite{LeeShrivastava09a,LeeShrivastava09c} proposed |
| problem. The first assigns variables depending on their lifetime to |
different solutions to cope with this problem. The first assigns |
| either the ECC protected or the unprotected part of a register file to |
variables depending on their lifetime to either the ECC protected or |
| balance energy consumption and reliability \cite{LeeShrivastava09a}. |
the unprotected part of a register file to balance energy consumption |
| The second spills registers to ECC protected memory if the register |
and reliability \cite{LeeShrivastava09a}. The second spills registers |
| contents are not used for a long period \cite{LeeShrivastava09c}. |
to ECC protected memory if the register contents are not used for a |
| |
long period \cite{LeeShrivastava09c}. There exist complete software |
| |
solutions which use different forms of code duplications |
| |
\cite{Oh+02a,Reis+05}, which do failure virtualization |
| |
\cite{WapplerMueller08} or which use techniques like control flow |
| |
checking \cite{Oh+02b}. A complete overview of processor description |
| |
languages and generation of compilers and simulators from processor |
| |
specifications gives the book of Mishra and Dutt \cite{MishraDutt08}. |
| |
A good survey of current instruction set simulators gives our chapter |
| |
in the \emph{Handbook of Signal Processing systems} \cite{BrHoKr09}. A |
| |
famous instruction set simulator with modelling of energy consumption |
| |
is \emph{Wattch} \cite{BrooksTiwariMartonosi00}. |
| |
|
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Methods for \emph{compiler verification} do exist |
| |
\cite{Langmaack97a,Po-lncs124,MMO-lncs1283,Goos:99:verifix,Goos:00:ASM,1328444}. |
| |
Most notably are the pioneering approaches of the |
| |
\emph{ProCoS} \cite{Langmaack96a} and the \emph{Verifix} |
| |
\cite{Goerigk-et-al:CC96,GlesnerGoosZimmeermann04,GoosZimmermann00} projects, and more recently of |
| |
the \emph{CompCert} project \cite{CompCert,BDL-fm06,Le-popl06}. There |
| |
is also a rich body of work on the related approaches of |
| |
\emph{translation validation} |
| |
\cite{Pnueli98a,Pnueli98b,Ne-pldi00,ZaksPnueli08}, |
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\emph{certifying compilation} |
| |
\cite{NL-pldi98,Colby-etal-pldi00,BlechPoetzsch07}, and |
| |
\emph{proof-carrying code} \cite{Ne-popl97,AF-popl00,FNSG-tlfi07}. |
| |
However, an integratedly verified compiler, which is optimizing and |
| |
ensures non-functional program properties such as on time and space |
| |
resources required by the compiled program is still |
| |
missing. Complementary to these approaches are approaches focusing on |
| |
frameworks for verifying compiler optimizations |
| |
\cite{781156,1040335,Kundu+09} or the verification of specific |
| |
compiler optimizations, such as the \emph{Lazy Code Motion} |
| |
\cite{TristanLeroy09} or instruction scheduling |
| |
\cite{TristanLeroy08}. By far more ambitious and a grand challenge for |
| |
computing research is Tony Hoare's vision of a \emph{verifying |
| |
compiler} which proves properties of the translated program |
| |
\cite{Hoare03}. |
| |
|
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\emph{Resource analysis}, especially worst-case execution time analysis $($WCET$)$ for real-time systems, which are often safety-critical, is a vibrant field of research in academia and industry and of fast growing economical relevance, |
| |
especially in the avionics and automotive industry. A survey on |
| |
state-of-the-art tools and methods for WCET analysis has recently been |
| |
given by Wilhelm et al.~\cite{Wilhelm:TECS2008}. The outcomes of the |
| |
WCET Tool Challenges \cite{Gus:ISoLA2006,Holsti:WCET2008}, however, |
| |
demonstrate that all these tools have their own strengths and |
| |
limitations. In particular, they all rely to some extent on |
| |
user-assistance and thus a \emph{trusted information basis} guiding |
| |
the WCET analysis \cite{Prantl:WCET2009}. |
| |
|
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|
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%\paragraph{AK} |
| |
%Three aspects of program and compiler correctness exist. The verifying |
| |
%compiler proves properties of the translated program and is a grand challenge |
| |
%for computing research \cite{Hoare03}. A certified compiler like Verifix is |
| |
%proven once to do semantically equivalent optimizations and translations |
| |
%\cite{GlesnerGoosZimmeermann04,GoosZimmermann00}. Translation validation proves |
| |
%at every compiler run that the translation is correct and was introduced by |
| |
%Pnueli et al.\ \cite{Pnueli98a,Pnueli98b} and Necula \cite{Necula00}. Until now |
| |
%some optimizations have been verified, recently lazy code motion |
| |
%\cite{TristanLeroy09}, instruction scheduling \cite{TristanLeroy08}, or the whole |
| |
%code generation phase \cite{BlechPoetzsch07}. Another research direction is the |
| |
%construction of general frameworks for validation \cite{ZaksPnueli08} or |
| |
%generalizations like parameterized equivalence checking \cite{Kundu+09}. |
| |
|
| %ADL and Instruction Set Simulators \cite{MishraDutt08} |
|
| |
|
| Compiler Verification \cite{Hoare,1328444,1314860} |
|
| |
|
| WCET \cite{} |
|
| |
|
| \subsubsection*{Previous achievements:} |
\subsubsection*{Previous achievements:} |
| %\emph{Brief description of your own contributions to the related |
%\emph{Brief description of your own contributions to the related |
| %scientific state-of-the art (5-10 lines)} |
%scientific state-of-the art (5-10 lines)} |
| Jens Knoop has a long history on work on program analysis with topics |
Jens Knoop's research focuses on proven correct and optimal program |
| like partial redundancy elimination or lazy code motion |
analyses and optimizations \cite{Kn-lncs1428}. He is the co-inventor |
| \cite{knoop:DSP:2008:1575,conf/cc/XueK06,scholz04}. Recently he |
of the \emph{Lazy Code Motion} |
| changed his research focus on worst case execution time analysis |
\cite{KRS-pldi92,KRS-retrolcm04,XueK06}, and numerous other program |
| \cite{SchrSchoKn09,Prantl:WLPE2008,prantl_et_al:DSP:2008:1661, |
analyses and optimizations including |
| kirner_et_al:DSP:2008:1657,kirner_et_al:DSP:2007:1197}. He is involved |
\emph{partial dead-code elimination} \cite{KRS-pldi94} and |
| in the organization of many compiler conferences and since 2002 program |
\emph{partially redundant assignment elimination} \cite{KRS-pldi94}, |
| cochair of the yearly workshop on compiler optimization meets verification. |
which are now part of state-of-the-art compilers. Regarding the |
| |
present PP, particularly important are the achievements on |
| |
resource-aware program analyses and optimizations including the |
| |
code-size sensitive \emph{Sparse Code Motion} \cite{RKS-popl00}, and its |
| |
counterpart for \emph{Speculative Code Motion} \cite{scholz04}. |
| |
Recent research in the frame of the FWF project CoSTA and the EU FP7 |
| |
project ALL-TIMES focuses on compiler support for |
| |
\emph{worst-case execution time analysis} for safety-critical |
| |
real-time embedded systems |
| |
\cite{Prantl:WCET2009,SchrSchoKn09,Prantl:WLPE2008,prantl_et_al:DSP:2008:1661,kirner_et_al:DSP:2008:1657,kirner_et_al:DSP:2007:1197}. |
| |
|
| |
% He served on $50+$ |
| |
%programme committees of international conferences including PLDI, CC, |
| |
%TACAS, Formal Methods, and Supercomputing. He was the General Chair of |
| |
%PLDI'02 and ETAPS'06, and is Programme Committee Co-Chair of PACT'10. He is the |
| |
%iniator and co-founder of the annual workshop series on |
| |
%\emph{Compiler Optimization meets Compiler Verification} (since 2002), |
| |
%co-organizer of 4 Dagstuhl seminars, most recently on \emph{Verifying |
| |
%Optimizing Compilation}, and a member of the European Network of |
| |
%Excellence HiPEAC. |
| |
%, and the IFIP WG 2.4 \emph{Software Implementation Technology}. |
| |
|
| Andreas Krall does research in the area of architecture description |
Andreas Krall does research in the area of architecture description |
| languages and the automatic generation of highly optimizing compilers, |
languages and the automatic generation of highly optimizing compilers, |
| specification of a processor \cite{BrFeKrRi09,BrEbKr07,FaKrHo07, |
specification of a processor \cite{BrFeKrRi09,BrEbKr07,FaKrHo07, |
| FarKrStBrand06,Krall+04micro}. An important focus is on optimization |
FarKrStBrand06,Krall+04micro}. An important focus is on optimization |
| techniques for embedded processors |
techniques for embedded processors |
| \cite{EbBrSchKrWiKa08,MeKr07,PrKrHo06,HiKr03} as he lead the Christian |
\cite{EbBrSchKrWiKa08,MeKr07,PrKrHo06,HiKr03} as he leads the Christian |
| Doppler research laboratory {\em compilation techniques for embedded |
Doppler research laboratory {\em compilation techniques for embedded |
| processors} with partners from industry (Infineon, OnDemand |
processors} with partners from industry (Infineon, OnDemand |
| Microelectronics). |
Microelectronics). |
| |
|
| |
The PP is designed to synergetically combine the complementary |
| |
expertises of Jens Knoop on verified resource-aware program analyses |
| |
and optimizations and of Andreas Krall on compilation techniques for |
| |
embedded processors. Their complementary expertise is essential for |
| |
the PP. |
| |
|
| |
|
| \subsubsection*{Goals (first 4 years):} |
\subsubsection*{Goals (first 4 years):} |
| %\emph{Description of the research |
%\emph{Description of the research |
| %topics to be addressed during the first 4 years. Make sure to explicitly |
%topics to be addressed during the first 4 years. Make sure to explicitly |
| %stress what the significant additions to the scientific knowledge are, |
%stress what the significant additions to the scientific knowledge are, |
| %and why they are important. (30-40 lines)} |
%and why they are important. (30-40 lines)} |
| |
The goals of the first 4 years are as follows: |
| |
|
| New modeling and representation techniques of non-functional program and system properties on the programming and intermediate language levels |
\begin{itemize} |
| Definitions and measures of non-functional program and system properties (performance, time, space/memory, power, concurrency). |
\item New modeling and representation techniques of non-functional |
| Modeling and representation of these properties alongside with the programming languages semantics |
program and system properties on the programming and |
| Adapting and enhancing state-of-the-art compilation techniques towards non-functional property and platform awareness |
intermediate language levels |
| New functional and non-functional property and platform-aware compilation techniques |
\item Definitions and measures of non-functional program and system |
| Analyses for non-functional program and system properties |
properties (performance, time, space/memory, power, |
| Functional and non-functional property and platform-aware code generation techniques |
concurrency). |
| Enabling validation and verification throughout the compilation process |
\item Modeling and representation of these properties alongside |
| Techniques for reducing or eliminating trusted code, annotation, etc., bases |
with the programming languages semantics |
| |
\item Adapting and enhancing state-of-the-art compilation techniques |
| |
towards non-functional property and platform awareness |
| |
\item New functional and non-functional property and platform-aware |
| |
compilation techniques |
| |
\item Analyses for non-functional program and system properties |
| |
\item Functional and non-functional property and platform-aware |
| |
code generation techniques |
| |
\item Enabling validation and verification throughout the compilation |
| |
process |
| |
\item Techniques for reducing or eliminating trusted code, |
| |
annotation, etc., bases |
| |
\end{itemize} |
| |
These goals are essential for making the development and the |
| |
compilation of embedded systems software more reliable and |
| |
robust. Moreover, they are the basis for the second 4 years extension |
| |
of the project. |
| |
|
| |
|
| \subsubsection*{Work Plan (first 4 years):} |
\subsubsection*{Work Plan (first 4 years):} |
| %you intend to conduct the actual research during the first 4 years. Be sure |
%you intend to conduct the actual research during the first 4 years. Be sure |
| %to also describe and (coarsely) quantify the resources (staff, cost of |
%to also describe and (coarsely) quantify the resources (staff, cost of |
| %special equipment) required for this work in a table. (20-30 lines)} |
%special equipment) required for this work in a table. (20-30 lines)} |
| |
Compilation techniques for robust embedded systems comprise different |
| |
areas. Therefore, the project is divided into three work packages: |
| |
\emph{compilation and simulation techniques for reliability}, \emph{verified |
| |
compilation} and \emph{resource analysis}. |
| |
|
| |
\paragraph*{WP1 - Compilation and Simulation Techniques for Reliability} |
| |
|
| |
In previous work we have developed a processor description language |
| |
with a very concise semantics from where we automatically generate |
| |
optimized compilers \cite{BrEbKr07} and high efficient instruction set |
| |
simulators \cite{BrFeKrRi09}. This environment we use as testbed for |
| |
our compiler optimizations for embedded processors |
| |
\cite{EbBrSchKrWiKa08,PrKrHo06,MeKr07}. We will extend this |
| |
environment to do research on compilation and simulation techniques to |
| |
enhance the reliability of processor/memory systems by mixed |
| |
hardware/software and pure software techniques. |
| |
|
| |
\begin{itemize} |
| |
\item Specification method to specify an energy consumption model in |
| |
a processor specification. |
| |
\item Specification method for redundancy and error correction in the |
| |
processor specification |
| |
\item Specification method for fault injection and fault checking in |
| |
the processor specification |
| |
\item Generation of optimized instruction set simulators from the |
| |
extended processor specification |
| |
\item Generation of optimizing compilers from the extended processor |
| |
specification |
| |
\item Research into new compiler optimizations to increase reliability by |
| |
pure software solutions, mixed hardware/software solutions and |
| |
balancing performance, code space, reliability and energy consumption |
| |
\item Research of correctness proofs and validation of the new optimizations |
| |
|
| |
\end{itemize} |
| |
|
| (1) Specification and efficient simulation of reliable processors (partial redundancy, |
\paragraph*{WP2 - Verified Compilation} |
| ECC, lockstep etc) and compiler optimizations to exploit/balance reliabiliy features. |
|
| Connection with CESAR NN1 |
Suitable semantics are necessary which support efficient translation |
| |
validation or support easy verification of a compiler. We will |
| |
research into different semantics and into mappings between the |
| |
semantics of our processor description language \cite{BrEbKr07} and a |
| |
compiler backend semantics, intermediate representation semantics |
| |
(compatible to LLVM) and source language semantics. The main research |
| |
will be on verification and translation validation for all kinds of |
| |
compiler optimizations. |
| |
|
| |
\begin{itemize} |
| |
\item Evaluate different semantics regarding suitability for compiler |
| |
verification and translation validation, eventually develop new |
| |
semantics |
| |
\item Develop a translator for an automatic mapping from our processor |
| |
description language into verification semantics |
| |
\item Develop a validation system from the intermediate representation |
| |
(LLVM) to the processor semantics |
| |
\item Develop a validation system from the source language (C) to the |
| |
intermediate representation (LLVM) |
| |
\item Research into verification and translation validation for different |
| |
frontend and backend optimizations |
| |
\end{itemize} |
| |
|
| |
\paragraph*{WP3 - Resource Analysis} |
| |
For safety-critical real-time embedded sytems resource consumption |
| |
measured in terms of a quantitative aspect of a program execution such |
| |
as execution time, storage use, and power consumption belongs rather |
| |
to the functional properties of an application rather its |
| |
non-functional ones. Formal guarantees on resource consumption are |
| |
thus essential and mandatory to ensure the robustness of such |
| |
systems. This requires new and usually more complex but more |
| |
expressive program analyses and transformations to support the (1) |
| |
programmer during source code development by early and automatically |
| |
providing hints on resource consumption and (2) the compiler to |
| |
optimize for resource consumption. In our previous work we focused on |
| |
compiler support for |
| |
\emph{worst-case execution time analysis $($WCET$)$} \cite{Prantl:WCET2009,Prantl:WLPE2008,prantl_et_al:DSP:2008:1661,kirner_et_al:DSP:2008:1657}. Based on this work we will extend this research towards |
| |
other quantitive aspects of resource consumption, especially storage |
| |
usage, towards these two global objectives, using the programming |
| |
environment used there as testbed for implementation |
| |
\cite{Prantl:WCET2009,Prantl:WLPE2008,prantl_et_al:DSP:2008:1661,kirner_et_al:DSP:2008:1657}. |
| |
|
| |
\begin{itemize} |
| |
\item Research into new program analyses for providing high-quality |
| |
bounds on resourse consumption which are useful for both the |
| |
application programmer and the compiler. |
| |
\item Research new program analyses and static optimizations |
| |
to optimize for resource consumption and to help complying to |
| |
possibly given limits. |
| |
\item Research suitable abstraction levels of interfaces and modes |
| |
of interaction between fully automatic program analysis and |
| |
verification methods and semi-automatic ones relying on |
| |
user-assistance because of undecidability issues |
| |
\item Research the synergies and the trade-off between fully |
| |
automatic program analysis and verification methods and |
| |
semi-automatic ones utilizing user-assistance on high-quality |
| |
resource bounds and the computational costs to compute them. |
| |
\item Research simulation and profiling methods to assess the |
| |
quality of resource consumption analyses and to support |
| |
correctness and security checks at run-time. |
| |
\end{itemize} |
| |
Overall, this WP will contribute to the design, foundations, |
| |
verification, implementation, and application of resource analyses. |
| |
|
| (2) translation verification, specification of semantics of IRs solving |
|
| subproblems. NN1 + NN2 |
|
| |
|
| (3) WCET NN3 |
|
| |
|
| |
|
| \begin{tabular}{llll} |
\begin{tabular}{llll} |
| |
\\ |
| \hline |
\hline |
| {\bf Pos} & {\bf Type} & {\bf Description} & {\bf Duration} \\ |
{\bf Pos} & {\bf Type} & {\bf Description} & {\bf Duration} \\ |
| NN1 & PhD & reliable compilation / simulation & 4 years \\ |
NN1 & PhD & reliable compilation / simulation & 4 years \\ |
| NN2 & PhD & compiler verificationi & 4 years \\ |
NN2 & PhD & verified compilation & 4 years \\ |
| NN3 & PhD & WCET & 4 years \\ |
NN3 & PhD & resource analysis & 4 years \\ |
| \hline |
\hline |
| \end{tabular} |
\end{tabular} |
| |
|
| |
|
| \subsubsection*{Goals (last 4 years):} |
\subsubsection*{Goals (last 4 years):} |
| %\emph{Brief description of the |
%\emph{Brief description of the |
| %eesearch topics to be addressed during the last 4 years. Make sure to |
%research topics to be addressed during the last 4 years. Make sure to |
| %explicitly stress what the significant additions to the scientific |
%explicitly stress what the significant additions to the scientific |
| %knowledge are, and why they are important. (20-30 lines)} |
%knowledge are, and why they are important. (20-30 lines)} |
| |
|
| New programming languages and compilers for RESs |
In the last 4 years we will extend the research of the first years into |
| Non-functional properties and requirements as first-class language and compiler citizens |
some additional directions like |
| New compilation techniques enabling a uniform and integrated approach |
|
| |
\begin{itemize} |
| |
\item New programming languages and compilers for RESs |
| |
\item Non-functional properties and requirements as first-class language and |
| |
compiler citizens |
| |
\item New compilation techniques enabling a uniform and integrated approach |
| for ensuring functional and non-functional program and system requirements |
for ensuring functional and non-functional program and system requirements |
| Replacing trust by proof |
\item Verified compilers, proof-carrying code, verifying compilation for RESs |
| Certifying compilation, proof-carrying code, translation validation |
\item Making legacy applications fit to and available on RESs |
| Verified compilers, verifying compilation for RESs |
\item Techniques for adjusting and decompiling legacy applications |
| Making legacy applications fit to and available on RESs |
\end{itemize} |
| Techniques for adjusting and decompiling legacy applications |
|
| |
Application of the results of this research reduces the cost of the |
| |
development of reliable and correct embedded systems and makes them |
| |
safer and robust. |
| |
|
| \subsubsection*{Collaboration with other PPs:} |
\subsubsection*{Collaboration with other PPs:} |
| %\emph{List the PPs you are expecting to collaborate with, and describe briefly |
%\emph{List the PPs you are expecting to collaborate with, and describe briefly |
| Links to specification and modeling of timing properties, to execution |
Links to specification and modeling of timing properties, to execution |
| models, hardware and software models. |
models, hardware and software models. |
| \item PP Composition and Predictability in RES Architectures |
\item PP Composition and Predictability in RES Architectures |
| [E182/Puschner]: Links to hard- and software models for time |
[E182.1/Puschner]: Links to hard- and software models for time |
| predictable systems, verification of timing behaviour. |
predictable systems, verification of timing behaviour. |
| \item PP Formal Verification for Robustness [E184/Veith]: Links to software |
\item PP Formal Verification for Robustness [E184/Veith]: Links to software |
| model checking and testing of code (on source code and intermediate |
model-checking and testing of code (on source code and intermediate |
| code levels), support for program analysis and transformation. |
code levels), support for program analysis and transformation. |
| \item PP Modeling \& Analysis of Robust Distributed Systems [E182/Schmid]: |
\item PP Modeling \& Analysis of Robust Distributed Systems [E182.2/Schmid]: |
| Links to functional and non-functional system requirements, |
Links to functional and non-functional system requirements, |
| distribution, concurrency. |
distribution, concurrency. |
| \end{itemize} |
\end{itemize} |
| %\emph{List envisioned international and national collaborations, and |
%\emph{List envisioned international and national collaborations, and |
| %describe briefly the topic and nature of such a collaboration. (5-10 |
%describe briefly the topic and nature of such a collaboration. (5-10 |
| %lines)} |
%lines)} |
| |
\begin{itemize} |
| Aviral Shrivastava, Arizona State University, Tempe, AZ, USA |
\item Walter Binder, University of Lugano, Switzerland (resource analysis) |
| |
\item Sabine Glesner, TU Berlin, Berlin, Germany (verified compilation) |
| Wolf Zimmermann, Universit\"at Halle, Halle, Germany |
\item Aviral Shrivastava, Arizona State University, Tempe, AZ, USA (reliable compilation) |
| |
\item Wolf Zimmermann, Martin-Luther Universit\"at Halle-Wittenberg, Halle, Germany |
| |
(verified compilation) |
| |
\end{itemize} |
| |
|
| \begin{comment} |
\begin{comment} |
| %Bitte hier die Bibtex-Entries einfuellen, z.B., |
%Bitte hier die Bibtex-Entries einfuellen, z.B., |