1,315 research outputs found
Parallel Architectures for Planetary Exploration Requirements (PAPER)
The Parallel Architectures for Planetary Exploration Requirements (PAPER) project is essentially research oriented towards technology insertion issues for NASA's unmanned planetary probes. It was initiated to complement and augment the long-term efforts for space exploration with particular reference to NASA/LaRC's (NASA Langley Research Center) research needs for planetary exploration missions of the mid and late 1990s. The requirements for space missions as given in the somewhat dated Advanced Information Processing Systems (AIPS) requirements document are contrasted with the new requirements from JPL/Caltech involving sensor data capture and scene analysis. It is shown that more stringent requirements have arisen as a result of technological advancements. Two possible architectures, the AIPS Proof of Concept (POC) configuration and the MAX Fault-tolerant dataflow multiprocessor, were evaluated. The main observation was that the AIPS design is biased towards fault tolerance and may not be an ideal architecture for planetary and deep space probes due to high cost and complexity. The MAX concepts appears to be a promising candidate, except that more detailed information is required. The feasibility for adding neural computation capability to this architecture needs to be studied. Key impact issues for architectural design of computing systems meant for planetary missions were also identified
Safe Recursion on Notation into a Light Logic by Levels
We embed Safe Recursion on Notation (SRN) into Light Affine Logic by Levels
(LALL), derived from the logic L4. LALL is an intuitionistic deductive system,
with a polynomial time cut elimination strategy.
The embedding allows to represent every term t of SRN as a family of proof
nets |t|^l in LALL. Every proof net |t|^l in the family simulates t on
arguments whose bit length is bounded by the integer l. The embedding is based
on two crucial features. One is the recursive type in LALL that encodes Scott
binary numerals, i.e. Scott words, as proof nets. Scott words represent the
arguments of t in place of the more standard Church binary numerals. Also, the
embedding exploits the "fuzzy" borders of paragraph boxes that LALL inherits
from L4 to "freely" duplicate the arguments, especially the safe ones, of t.
Finally, the type of |t|^l depends on the number of composition and recursion
schemes used to define t, namely the structural complexity of t. Moreover, the
size of |t|^l is a polynomial in l, whose degree depends on the structural
complexity of t.
So, this work makes closer both the predicative recursive theoretic
principles SRN relies on, and the proof theoretic one, called /stratification/,
at the base of Light Linear Logic
Weak reduction and garbage collection in interaction nets
This paper presents an implementation device for the weak reduction of interaction nets to interface normal form. The results produced by running several benchmarks are given, suggesting that weak reduction greatly improves the performance of the interaction combinators-based implementation of the λ-calculus.(undefined
When Ambients Cannot be Opened
International audienceWe investigate expressiveness of a fragment of the ambient calculus, a formalism for describing distributed and mobile computations. More precisely, we study expressiveness of the pure and public ambient calculus from which the capability open has been removed, in terms of the reachability problem of the reduction relation. Surprisingly, we show that even for this very restricted fragment, the reachability problem is not decidable. At a second step, for a slightly weaker reduction relation, we prove that reachability can be decided by reducing this problem to markings reachability for Petri nets. Finally, we show that the name-convergence problem as well as the model-checking problem turn out to be undecidable for both the original and the weaker reduction relation. The authors are grateful to S. Tison and Y. Roos for fruitful discussions and thank the anony mous ferees for valuable comments. This work is supported by an ATIP grant from CNRS
Adaptable processes
We propose the concept of adaptable processes as a way of overcoming the
limitations that process calculi have for describing patterns of dynamic
process evolution. Such patterns rely on direct ways of controlling the
behavior and location of running processes, and so they are at the heart of the
adaptation capabilities present in many modern concurrent systems. Adaptable
processes have a location and are sensible to actions of dynamic update at
runtime; this allows to express a wide range of evolvability patterns for
concurrent processes. We introduce a core calculus of adaptable processes and
propose two verification problems for them: bounded and eventual adaptation.
While the former ensures that the number of consecutive erroneous states that
can be traversed during a computation is bound by some given number k, the
latter ensures that if the system enters into a state with errors then a state
without errors will be eventually reached. We study the (un)decidability of
these two problems in several variants of the calculus, which result from
considering dynamic and static topologies of adaptable processes as well as
different evolvability patterns. Rather than a specification language, our
calculus intends to be a basis for investigating the fundamental properties of
evolvable processes and for developing richer languages with evolvability
capabilities
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