Complexity Information Flow in a Multi-threaded Imperative Language

We propose a type system to analyze the time consumed by multi-threaded imperative programs with a shared global memory, which delineates a class of safe multi-threaded programs. We demonstrate that a safe multi-threaded program runs in polynomial time if (i) it is strongly terminating wrt a non-deterministic scheduling policy or (ii) it terminates wrt a deterministic and quiet scheduling policy. As a consequence, we also characterize the set of polynomial time functions. The type system presented is based on the fundamental notion of data tiering, which is central in implicit computational complexity. It regulates the information flow in a computation. This aspect is interesting in that the type system bears a resemblance to typed based information flow analysis and notions of non-interference. As far as we know, this is the first characterization by a type system of polynomial time multi-threaded programs

C programs for solving the time-dependent Gross-Pitaevskii equation in a fully anisotropic trap

We present C programming language versions of earlier published Fortran programs (Muruganandam and Adhikari, Comput. Phys. Commun. 180 (2009) 1888) for calculating both stationary and non-stationary solutions of the time-dependent Gross-Pitaevskii (GP) equation. The GP equation describes the properties of dilute Bose-Einstein condensates at ultra-cold temperatures. C versions of programs use the same algorithms as the Fortran ones, involving real- and imaginary-time propagation based on a split-step Crank-Nicolson method. In a one-space-variable form of the GP equation, we consider the one-dimensional, two-dimensional, circularly-symmetric, and the three-dimensional spherically-symmetric harmonic-oscillator traps. In the two-space-variable form, we consider the GP equation in two-dimensional anisotropic and three-dimensional axially-symmetric traps. The fully-anisotropic three-dimensional GP equation is also considered. In addition to these twelve programs, for six algorithms that involve two and three space variables, we have also developed threaded (OpenMP parallelized) programs, which allow numerical simulations to use all available CPU cores on a computer. All 18 programs are optimized and accompanied by makefiles for several popular C compilers. We present typical results for scalability of threaded codes and demonstrate almost linear speedup obtained with the new programs, allowing a decrease in execution times by an order of magnitude on modern multi-core computers.Comment: 8 pages, 1 figure; 18 C programs included (to download, click other and download the source

Model-checking Secure Information Flow for Multi-Threaded Programs

Abstract. This paper shows how secure information flow properties of multi-threaded programs can be verified by model checking in a precise and efficient way, by using the idea of self-composition. It discusses two properties that aim to capture secure information flow for multi-threaded programs, and it shows how these properties can be char-acterised in modal µ-calculus. For this characterisation, a self-composed model of the program is constructed. More precisely, this is a model that contains two copies of the labelled transition system induced by the program, so that the program is executed in parallel with itself. The self-composed model allows to compare two program executions in a single temporal formula that characterises a secure information flow property. Both the formula and model are translated into the input language for the Concurrency Workbench model checker. We discuss this encoding, and use it for some practical experiments on several simple examples.

Quantifying Timing Leaks and Cost Optimisation

We develop a new notion of security against timing attacks where the attacker is able to simultaneously observe the execution time of a program and the probability of the values of low variables. We then show how to measure the security of a program with respect to this notion via a computable estimate of the timing leakage and use this estimate for cost optimisation.Comment: 16 pages, 2 figures, 4 tables. A shorter version is included in the proceedings of ICICS'08 - 10th International Conference on Information and Communications Security, 20-22 October, 2008 Birmingham, U

Typing Noninterference for Reactive Programs

We propose a type system to enforce the security property of noninterference in a core reactive language, obtained by extending the imperative language of Volpano, Smith and Irvine with reactive primitives manipulating broadcast signals and with a form of ``scheduled'' parallelism. Due to the particular nature of reactive computations, the definition of noninterference has to be adapted. We give a formulation of noninterference based on bisimulation. Our type system is inspired by that introduced by Boudol and Castellani, and independently by Smith, to cope with timing leaks in a language for parallel programs with scheduling. We establish the soundness of this type system with respect to our notion of noninterference

Innovative all composite multi-pultrusion truss system for stressed arch deployable shelters

Trusses are one of the successful structural forms that have been utilised, at extended scale, since the nineteen century. Fibre composite materials are relatively new to civil engineering applications. The increased interest in using composites in civil applications can be attributed to advantages when compared to other construction materials that offset their associated costs. Using conventional approaches for truss systems in composite materials can undermine their efficiency. This is mainly due to concentration of stresses at connections which usually govern the truss design. The Military Modular Shelter System (M2S2) initiative is a research project that aims to develop a fibre composite re-deployable arched shelter system with rigid PVC or fabric cladding. The main frames are formed from modular fibre composite panels that are connected and stressed into position by prestressing cables. Different geometries can be obtained using this system by changing the number of panels per frame and the packer sizes between panels. This paper presents the development and testing of innovative fibre composite truss modules that were investigated as part of this project. The truss system is based on using multi-pultrusion sections for the chord and vertical members. Truss bracing is provided by a double skin laminated web. This structure offers many advantages including semi-ductile failure that occurred outside the joint area and ease of manufacturing. In spite of being developed for the M2S2 system, the concept is similarly applicable as a general purpose truss system

Complexity Information Flow in a Multi-threaded Imperative Language

International audienceWe propose a type system to analyze the time consumed by multi-threaded imperative programs with a shared global memory, which delineates a class of safe multi-threaded programs. We demon-strate that a safe multi-threaded program runs in polynomial time if (i) it is strongly terminating wrt a non-deterministic scheduling policy or (ii) it terminates wrt a deterministic and quiet scheduling policy. As a consequence, we also characterize the set of polynomial time functions. The type system presented is based on the fundamental notion of data tiering, which is central in implicit computational complexity. It regu-lates the information flow in a computation. This aspect is interesting in that the type system bears a resemblance to typed based informa-tion flow analysis and notions of non-interference. As far as we know, this is the first characterization by a type system of polynomial time multi-threaded programs