74,892 research outputs found
Geometric transitions between Calabi-Yau threefolds related to Kustin-Miller unprojections
We study Kustin-Miller unprojections between Calabi-Yau threefolds or more
precisely the geometric transitions they induce. We use them to connect many
families of Calabi-Yau threefolds with Picard number one to the web of Calabi
Yau complete intersections. This enables us to find explicit description of a
few known families of Calabi-Yau threefolds in terms of equations. Moreover we
find two new examples of Calabi-Yau threefolds with Picard group of rank one,
described by Pfaffian equations in weighted projective spaces.Comment: to appear in Journal of Geometry and Physic
Toatie : functional hardware description with dependent types
Describing correct circuits remains a tall order, despite four decades of evolution in Hardware Description Languages (HDLs).
Many enticing circuit architectures require recursive structures or complex compile-time computation — two patterns that prove difficult to capture in traditional HDLs. In a signal processing context, the Fast FIR Algorithm (FFA) structure for efficient parallel filtering proves to be naturally recursive, and most Multiple Constant Multiplication (MCM) blocks decompose multiplications into graphs of simple shifts and adds using demanding compile time computation. Generalised versions of both remain mostly in academic folklore. The implementations which do exist are often ad hoc circuit generators, written in software languages. These pose challenges for verification and are resistant to composition.
Embedded functional HDLs, that represent circuits as data, allow for these descriptions at the cost of forcing the designer to work at the gate-level. A promising alternative is to use a stand-alone compiler, representing circuits as plain functions, exemplified by the CλaSH HDL. This, however, raises new challenges in capturing a circuit’s staging — which expressions in the single language should be reduced during compile-time elaboration, and which should remain in the circuit’s run-time? To better reflect the physical separation between circuit phases, this work proposes a new functional HDL (representing circuits as functions) with first-class staging constructs.
Orthogonal to this, there are also long-standing challenges in the verification of parameterised circuit families. Industry surveys have consistently reported that only a slim minority of FPGA projects reach production without non-trivial bugs. While a healthy growth in the adoption of automatic formal methods is also reported, the majority of testing remains dynamic — presenting difficulties for testing entire circuit families at once.
This research offers an alternative verification methodology via the combination of dependent types and automatic synthesis of user-defined data types. Given precise enough types for synthesisable data, this environment can be used to develop circuit families with full functional verification in a correct-by-construction fashion. This approach allows for verification of entire circuit families (not just one concrete member) and side-steps the state-space explosion of model checking methods. Beyond the existing work, this research offers synthesis of combinatorial circuits — not just a software model of their behaviour. This additional step requires careful consideration of staging, erasure & irrelevance, deriving bit representations of user-defined data types, and a new synthesis scheme.
This thesis contributes steps towards HDLs with sufficient expressivity for awkward, combinatorial signal processing structures, allowing for a correct-by-construction approach, and a prototype compiler for netlist synthesis.Describing correct circuits remains a tall order, despite four decades of evolution in Hardware Description Languages (HDLs).
Many enticing circuit architectures require recursive structures or complex compile-time computation — two patterns that prove difficult to capture in traditional HDLs. In a signal processing context, the Fast FIR Algorithm (FFA) structure for efficient parallel filtering proves to be naturally recursive, and most Multiple Constant Multiplication (MCM) blocks decompose multiplications into graphs of simple shifts and adds using demanding compile time computation. Generalised versions of both remain mostly in academic folklore. The implementations which do exist are often ad hoc circuit generators, written in software languages. These pose challenges for verification and are resistant to composition.
Embedded functional HDLs, that represent circuits as data, allow for these descriptions at the cost of forcing the designer to work at the gate-level. A promising alternative is to use a stand-alone compiler, representing circuits as plain functions, exemplified by the CλaSH HDL. This, however, raises new challenges in capturing a circuit’s staging — which expressions in the single language should be reduced during compile-time elaboration, and which should remain in the circuit’s run-time? To better reflect the physical separation between circuit phases, this work proposes a new functional HDL (representing circuits as functions) with first-class staging constructs.
Orthogonal to this, there are also long-standing challenges in the verification of parameterised circuit families. Industry surveys have consistently reported that only a slim minority of FPGA projects reach production without non-trivial bugs. While a healthy growth in the adoption of automatic formal methods is also reported, the majority of testing remains dynamic — presenting difficulties for testing entire circuit families at once.
This research offers an alternative verification methodology via the combination of dependent types and automatic synthesis of user-defined data types. Given precise enough types for synthesisable data, this environment can be used to develop circuit families with full functional verification in a correct-by-construction fashion. This approach allows for verification of entire circuit families (not just one concrete member) and side-steps the state-space explosion of model checking methods. Beyond the existing work, this research offers synthesis of combinatorial circuits — not just a software model of their behaviour. This additional step requires careful consideration of staging, erasure & irrelevance, deriving bit representations of user-defined data types, and a new synthesis scheme.
This thesis contributes steps towards HDLs with sufficient expressivity for awkward, combinatorial signal processing structures, allowing for a correct-by-construction approach, and a prototype compiler for netlist synthesis
An Embedded Domain Specific Language to Model, Transform and Quality Assure Business Processes in Business-Driven Development
In Business-Driven Development (BDD), business process models are produced by business analysts. To ensure that the business requirements are satisfied, the IT solution is directly derived through a process of model refinement. If models do not contain all the required technical details or contain errors, the derived implementation would be incorrect and the BDD lifecycle would have to be repeated. In this project we present a functional domain specific language embedded in Haskell, with which: 1) models can rapidly be produced in a concise and abstract manner, 2) enables focus on the specifications rather than the implementation, 3) ensures that all the required details, to generate the executable code, are specified, 4) models can be transformed, analysed and interpreted in various ways, 5) quality assures models by carrying out three types of checks; by Haskell.s type checker, at construction-time and by functions that analyse the soundness of models, 6) enables users to define quality assured composite model transformations
Moduli spaces of abstract and embedded Kummer varieties
In this paper, we investigate the construction of two moduli stacks of Kummer
varieties. The first one is the stack of abstract
Kummer varieties and the second one is the stack of
embedded Kummer varieties. We will prove that is a
Deligne-Mumford stack and its coarse moduli space is isomorphic to , the coarse moduli space of principally polarized abelian varieties of
dimension . On the other hand we give a modular family
of embedded Kummer varieties embedded in , meaning that every geometric fiber of this family is an embedded
Kummer variety and every isomorphic class of such varieties appears at least
once as the class of a fiber. As a consequence, we construct the coarse moduli
space of embedded Kummer surfaces and
prove that it is obtained from by contracting a particular
curve inside this space. We conjecture that this is a general fact:
could be obtained from
via a contraction for all .Comment: 31 page
A New Approach for Quality Management in Pervasive Computing Environments
This paper provides an extension of MDA called Context-aware Quality Model
Driven Architecture (CQ-MDA) which can be used for quality control in pervasive
computing environments. The proposed CQ-MDA approach based on
ContextualArchRQMM (Contextual ARCHitecture Quality Requirement MetaModel),
being an extension to the MDA, allows for considering quality and
resources-awareness while conducting the design process. The contributions of
this paper are a meta-model for architecture quality control of context-aware
applications and a model driven approach to separate architecture concerns from
context and quality concerns and to configure reconfigurable software
architectures of distributed systems. To demonstrate the utility of our
approach, we use a videoconference system.Comment: 10 pages, 10 Figures, Oral Presentation in ECSA 201
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