On Characterizing the Data Movement Complexity of Computational DAGs for Parallel Execution

Technology trends are making the cost of data movement increasingly dominant, both in terms of energy and time, over the cost of performing arithmetic operations in computer systems. The fundamental ratio of aggregate data movement bandwidth to the total computational power (also referred to the machine balance parameter) in parallel computer systems is decreasing. It is there- fore of considerable importance to characterize the inherent data movement requirements of parallel algorithms, so that the minimal architectural balance parameters required to support it on future systems can be well understood. In this paper, we develop an extension of the well-known red-blue pebble game to develop lower bounds on the data movement complexity for the parallel execution of computational directed acyclic graphs (CDAGs) on parallel systems. We model multi-node multi-core parallel systems, with the total physical memory distributed across the nodes (that are connected through some interconnection network) and in a multi-level shared cache hierarchy for processors within a node. We also develop new techniques for lower bound characterization of non-homogeneous CDAGs. We demonstrate the use of the methodology by analyzing the CDAGs of several numerical algorithms, to develop lower bounds on data movement for their parallel execution

Hodge metrics and positivity of direct images

Building on Fujita-Griffiths method of computing metrics on Hodge bundles, we show that the direct image of an adjoint semi-ample line bundle by a projective submersion has a continuous metric with Griffiths semi-positive curvature. This shows that for every holomorphic semi-ample vector bundle $E$ on a complex manifold, and every positive integer $k$, the vector bundle $S^kE\otimes\det E$ has a continuous metric with Griffiths semi-positive curvature. If $E$ is ample on a projective manifold, the metric can be made smooth and Griffiths positive.Comment: revised and expanded version of "A positivity property of ample vector bundles

Solving the insecurity problem for assertions

In the symbolic verification of cryptographic protocols, a central problem is deciding whether a protocol admits an execution which leaks a designated secret to the malicious intruder. Rusinowitch & Turuani (2003) show that, when considering finitely many sessions, this ``insecurity problem'' is NP-complete. Central to their proof strategy is the observation that any execution of a protocol can be simulated by one where the intruder only communicates terms of bounded size. However, when we consider models where, in addition to terms, one can also communicate logical statements about terms, the analysis of the insecurity problem becomes tricky when both these inference systems are considered together. In this paper we consider the insecurity problem for protocols with logical statements that include {\em equality on terms} and {\em existential quantification}. Witnesses for existential quantifiers may be unbounded, and obtaining small witness terms while maintaining equality proofs complicates the analysis considerably. We extend techniques from Rusinowitch & Turuani (2003) to show that this problem is also in NP

Beyond Reuse Distance Analysis: Dynamic Analysis for Characterization of Data Locality Potential

Emerging computer architectures will feature drastically decreased flops/byte (ratio of peak processing rate to memory bandwidth) as highlighted by recent studies on Exascale architectural trends. Further, flops are getting cheaper while the energy cost of data movement is increasingly dominant. The understanding and characterization of data locality properties of computations is critical in order to guide efforts to enhance data locality. Reuse distance analysis of memory address traces is a valuable tool to perform data locality characterization of programs. A single reuse distance analysis can be used to estimate the number of cache misses in a fully associative LRU cache of any size, thereby providing estimates on the minimum bandwidth requirements at different levels of the memory hierarchy to avoid being bandwidth bound. However, such an analysis only holds for the particular execution order that produced the trace. It cannot estimate potential improvement in data locality through dependence preserving transformations that change the execution schedule of the operations in the computation. In this article, we develop a novel dynamic analysis approach to characterize the inherent locality properties of a computation and thereby assess the potential for data locality enhancement via dependence preserving transformations. The execution trace of a code is analyzed to extract a computational directed acyclic graph (CDAG) of the data dependences. The CDAG is then partitioned into convex subsets, and the convex partitioning is used to reorder the operations in the execution trace to enhance data locality. The approach enables us to go beyond reuse distance analysis of a single specific order of execution of the operations of a computation in characterization of its data locality properties. It can serve a valuable role in identifying promising code regions for manual transformation, as well as assessing the effectiveness of compiler transformations for data locality enhancement. We demonstrate the effectiveness of the approach using a number of benchmarks, including case studies where the potential shown by the analysis is exploited to achieve lower data movement costs and better performance.Comment: Transaction on Architecture and Code Optimization (2014

A Global Communication Optimization Technique Based on Data-Flow Analysis and Linear Algebra

Reducing communication overhead is extremely important in distributed-memory message-passing architectures. In this paper, we present a technique to improve communication that considers data access patterns of the entire program. Our approach is based on a combination of traditional data-flow analysis and a linear algebra framework, and works on structured programs with conditional statements and nested loops but without arbitrary goto statements. The distinctive features of the solution are the accuracy in keeping communication set information, support for general alignments and distributions including block-cyclic distributions and the ability to simulate some of the previous approaches with suitable modifications. We also show how optimizations such as message vectorization, message coalescing and redundancy elimination are supported by our framework. Experimental results on several benchmarks show that our technique is effective in reducing the number of messages (an average of 32% reduction), the volume of the data communicated (an average of 37% reduction), and the execution time (an average of 26% reduction)

Thin Layer Chromatography of Pesticides and Their Residues

Recent progress in the analysis of organo-phosphorus, organo-chlorine, carbamate, urea, uracil pesticides and their residues by thin layer chromatorgraphic methods employing chemical and enzymatic methods is reviewed

Solvothermal nanoYAG synthesis: Mechanism and particle growth kinetics

This paper was accepted for publication in the journal Journal of Supercritical Fluids and the definitive published version is available at http://dx.doi.org/10.1016/j.supflu.2015.09.031NanoYAG particles with spherical morphology have been synthesised using a solvothermal method; a structure sensitive reaction, where the chemical reaction and the particle growth kinetics are interdependent. It has been observed that the primary YAG particles agglomerated into ∼30 nm clusters via a self-assembled Ostwald ripening process along (2 1 1) planes, separated by a distance of ∼0.49 nm, at 270 °C and 2.0 MPa for 2 h. These nanoclusters coalesced into single nanoparticles of ∼30 nm in size and exhibited a smaller inter planar distance of ∼0.26 nm, corresponding to the (4 2 0) planes, when synthesized at 300 °C and 8.5 MPa for 2 h. in addition, the solvent 1,4-butanediol transformed into 1,4-diacetoxybutane, this will have undergone esterification by reacting with the terminal acetate groups cleaved from the precursor, yttrium acetate. The proposed mechanism based on the analytical evidence suggests that a complete dissolution of precursors facilitated the structural re-arrangement of atoms within the planes and lead to a significantly higher degree of crystallinity. Moreover, once the particles with (4 2 0) planes had formed, they were no longer involved in facile coalescence along their preferential planes due to their lower interfacial energy compared to the (2 1 1) planes. This led to control of the particle morphology and with little agglomeration occurring in the final nanopowder

Development of DNA probes for M. tuberculosis

Attempts were made to develop DNA probes for M. tuberculosis. Random library of M. tuberculosis was constructed in plasmid pGEM -4. Selection of recombinant clones was made by hybridisation with 32P labelled M. tuberculosis probe. Ten recombinant clones were selected on the basis of strong signals from the random library. These 10 clones named pTRC1-10 were subjected to tests for specificity and sensitivity. On this basis, pTRC4 was chosen and this is also, useful in restriction fragment length polymorphism (RFLP) studies

Seismic Response Control Systems for Structures

Structures constructed in developing world are typically RC frames with masonry infill. These structures have little resistance for lateral loads caused by earthquake and wind. Even for  adequately designed structures also, due to permissible deformation beyond elastic limits, failure of masonry causes severe loss of life and property. In the case of structures designed to sustain excessive deformation such as of defence establishments, functioning and serviceability of machines and equipment installed therein are adversely affected. This co-lateral damage may be reduced by adopting another design philosophy of structure response control. In this methodology, a supplementary damping device is incorporated in the primary structure, which absorbs most of the seismic energy imparted to it, restricting the structural response within serviceable limits. These devices may be passive, active, semi-active or hybrid types. Other than passive all options are technology-intensive and dependent on external energy source, not a favourable proposition for developing nations. Among all the passive devices, tuned liquid dampers (TLDs) promise to be most suitable. Here, existing overhead water tanks (OHWT) may be used as TLD with slight adjustment and modification. This method will be able to control the structural response without putting any extra load on the existing or newly-designed buildings. This paper reviews various types of dampers and discusses evolution of tuned liquid dampers. A method has also been proposed for incorporating TLDs in existing and new structures. This methodology may be very useful for structures of defence establishment which are scattered and remotely placed by location, housing important equipments sensitive to vibrations, as it is free from external power dependence and regular maintenance.Defence Science Journal, 2009, 59(3), pp.239-251, DOI:http://dx.doi.org/10.14429/dsj.59.151