Symbolic execution is a powerful, systematic analysis that has received much visibility in the last decade. Scalability however remains a major challenge for symbolic execution. Compositional analysis is a well-known general purpose methodology for increasing scalability. This thesis introduces a new approach for compositional symbolic execution. Our key insight is that we can summarize each analyzed method as a memoization tree that captures the crucial elements of symbolic execution, and leverage these memoization trees to efficiently replay the symbolic execution of the corresponding methods with respect to their calling contexts. Memoization trees offer a natural way to compose in the presence of heap operations, which cannot be dealt with by previous work that uses logical formulas as summaries for composi- tional symbolic execution. Our approach also enables an efficient treatment of error traces by short-circuiting the execution of paths that lead to them. Our preliminary experimental evaluation based on a prototype implementation in Symbolic PathFinder shows promising results. / text

Thesis advisor: Alfredo Urzua / Thesis advisor: John Ebel / Nine empirical equations that estimate saturated hydraulic conductivity as a func- tion of grain size in well-graded sands with gravels having large uniformity coecients (U > 50) are evaluated by comparing their accuracy when predicting observed conduc- tivities in constant head permeability tests. According to the ndings of this thesis, in decreasing order of accuracy these equations are: USBR (Vukovic and Soro, 1992; USBR, 1978), Hazen (Hazen, 1892), Slichter (Slichter, 1898), Kozeny-Carman (Carrier, 2003), Fair and Hatch (Fair and Hatch, 1933), Terzaghi (Vukovic and Soro, 1992), Beyer (Beyer, 1966), Kruger (Vukovic and Soro, 1992), and Zunker (Zunker, 1932). These re- sults are based on multiple constant head permeability tests on two samples of granular material corresponding to well-graded sands with gravels. Using the USBR equation sat- urated hydraulic conductivities for a statistical population of 874 samples of well-graded sands with gravels forming 29 loads from a heap leaching mine in northern Chile are calculated. Results indicate that, using the USBR equation, on average the hydraulic conductivity of the leaching heaps has a two standard deviation range between 0.18 and 0.15 cm/s. Permeability tests on the actual material used in the heaps provided by the mine shows that the results presented in this thesis are consistent with actual observa- tions and represent saturated conductivities in heaps up to 3 m high under a pressures of up to 62 Kpa. In future work hydraulic conductivities can be combined with water retention curves, discharge rates, irrigation rates, porosities, and consolidation so as to evaluate the relationship between copper yields and the hydraulic conductivities of the heap. / Thesis (MS) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "December, 2007." Includes bibliographical references (leaves 166-176). Online version available on the World Wide Web.

Dynamic features of programming languages such as dynamic type system, dynamic method calls, dynamic code execution, and dynamic data structures provide the flexibility which can accelerate the development, but on the other hand they reduce the information that is checked at compile time and thus make programs more error-prone and less efficient. While the problem of lacking compile time checks can be partially addressed by techniques of static analysis, dynamic features pose major challenges for these techniques sacrificing their precision, soundness, and scalability. To tackle this problem, we propose a framework for static analysis that automatically resolves these features and thus allows defining sound and precise static analyses similarly as the analyzed program would not use these functions. To build the framework, we propose a novel heap analysis that models associative arrays and dynamic (prototype) objects. Next, we propose value analysis providing additional information necessary to resolve dynamic features. Finally, we propose a technique that automatically and generically combines value analysis and a heap analysis modeling associative arrays and prototype objects. Powered by TCPDF (www.tcpdf.org)

The recovery of mineral from ore in the heap leaching process requires the mineral to come into contact with the leaching solution. However, heap hydrology is prone to non-uniform behaviour due to the inhomogeneity of the ore particles and the heap structure. The primary aim of this thesis was therefore to develop a magnetic resonance imaging (MRI) technique which would allow for the novel non-invasive imaging of the liquid hold-up in representative laboratory-scale heap leaching systems. The ferro- and paramagnetic species in the ore were found to cause significant distortions in frequency encoded MRI acquisitions. These distortions were mitigated through the application of single point imaging techniques. Comparison with equivalent X-ray CT acquisitions, which are immune to magnetic susceptibility distortions, confirmed the accuracy of the single point acquisitions. Spin echo single point imaging (SESPI) was demonstrated to be more robust than the simple single point imaging (SPI) technique because the effect of $\textit{T}$$_{2}$ weighting on the MRI signal was less significant than that of $\textit{T}$$_{2}$*. Mapping of the gas, liquid and solid distributions in unsaturated leaching columns using SESPI allowed for the quantification of the hold-up and voidage values. These compared favourably to gravimetric measurements and literature values, thereby confirming their validity. Novel measurement of the liquid film thickness and the interfacial areas between the three phases was achieved and insight into the liquid behaviour was obtained through different flow rate experiments as well as MRI tracer experiments. Drip irrigation of the ore was considered for beds of large, fine and agglomerated ore. Liquid distribution in the fine ore closely resembled that of irrigation of clay soils whereas flow through the large ore was gravity dominated. Slumping of the agglomerated ore caused permanent limitation of the liquid distribution and the effect of flow rate changes was observed to be limited to the region below the irrigation point. In both the column and drip irrigation experiments, increases in the liquid flow rate caused small increases in the liquid hold-up in the form of new, relatively thicker rivulets, thereby improving the liquid-solid interfacial area. However it did not affect capillary held liquid volume so the effect of flow rate changes decreased as the lateral distance from the irrigation point increased. Finally, X-ray CT images of a long term ferric leach were analysed to assess the factors affecting the mineral leaching. Proximity of the mineral to the ore surface was found to be the critical factor, as only mineral located within 2 mm of the surface was recovered, though liquid distribution effects were also observed.

The dual heap virtual implementation provided a new base for memory organization such that the heap storage can be virtually enlarged to include the extremely large disk space. Two simulation models were used to investigate aging in physical space as well as the dual heap implementation. The simulators generated results which measured the ability of each method to detect leaks generate false positives and false negatives. In comparison, the dual heap implementation showed a relatively better performance than the aging algorithm. The dual heap implementation is shown to produce less false positives and less false negatives. It has better capability of detecting memory leaks. Furthermore, dual heap implementation extends the space provide to the main heap such that programs with greedy memory consumption can also benefit from this implementation. The dual heap virtual model of the heap organization is a promising architecture, which at once masks the memory leak problem and extends the heap storage for greedy programs. The introduction and advancement of 64-bit address machine would not reduce the value of the dual virtual heap implementation, for the simple reasons that a large number of legacy programs will continue to run in a 32-bit environment, and for the fact that greedy programs and leaks will drain the heap storage of 64-bit machines as much as they did for the 32-bit machines.

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This thesis discusses cache oblivious data structures. These are structures which have good caching characteristics without knowing Z, the size of the cache, or L, the length of a cache line. Since the structures do not require these details for good performance they are portable across caching systems. Another advantage of such structures isthat the caching results hold for every level of cache within a multilevel cache. Two simple data structures are studied; the array used for binary search and the linear list. As well as being cache oblivious, the structures presented in this thesis are space efficient, requiring little additional storage. We begin the discussion with a layout for a search tree within an array. This layout allows Searches to be performed in O(log n) time and in O(log n/log L) (the optimal number) cache misses. An algorithm for building this layout from a sorted array in linear time is given. One use for this layout is a heap-like implementation of the priority queue. This structure allows Inserts, Heapifies and ExtractMaxes in O(log n) time and O(log nlog L) cache misses. A priority queue using this layout can be builtfrom an unsorted array in linear time. Besides the n spaces required to hold the data, this structure uses a constant amount of additional storage. The cache oblivious linear list allows scans of the list taking Theta(n) time and incurring Theta(n/L) (the optimal number) cache misses. The running time of insertions and deletions is not constant, however it is sub-polynomial. This structure requires e*n additional storage, where e is any constant greater than zero.

This thesis discusses cache oblivious data structures. These are structures which have good caching characteristics without knowing Z, the size of the cache, or L, the length of a cache line. Since the structures do not require these details for good performance they are portable across caching systems. Another advantage of such structures isthat the caching results hold for every level of cache within a multilevel cache. Two simple data structures are studied; the array used for binary search and the linear list. As well as being cache oblivious, the structures presented in this thesis are space efficient, requiring little additional storage. We begin the discussion with a layout for a search tree within an array. This layout allows Searches to be performed in O(log n) time and in O(log n/log L) (the optimal number) cache misses. An algorithm for building this layout from a sorted array in linear time is given. One use for this layout is a heap-like implementation of the priority queue. This structure allows Inserts, Heapifies and ExtractMaxes in O(log n) time and O(log nlog L) cache misses. A priority queue using this layout can be builtfrom an unsorted array in linear time. Besides the n spaces required to hold the data, this structure uses a constant amount of additional storage. The cache oblivious linear list allows scans of the list taking Theta(n) time and incurring Theta(n/L) (the optimal number) cache misses. The running time of insertions and deletions is not constant, however it is sub-polynomial. This structure requires e*n additional storage, where e is any constant greater than zero.

Discrete Event Simulation on GPUs employing parallel heap data structure is the focus of this thesis. Two traditional algorithms, one being conservative and other being optimistic, for parallel discrete event simulation have been implemented on GPUs using CUDA. The first algorithm is the safe-window algorithm (conservative). It has produced expected performance when compared to sequential simulation. The second algorithm, known as SyncSim, is an optimistic simulation algorithm previously designed to be space efficient and reduce rollbacks. This algorithm is re-implemented on GPU platform with necessary changes on the logic simulator and the parallel heap implementation. The performance of the parallel heap when working with a logic simulator has also been validated against the results indicated in previous research paper on parallel heap without the logic simulator.