Many simulation data sets are so massive that they must be distributed among disk farms attached to different computing nodes. The data is partitioned into spatially disjoint sets that are not easily transferable among nodes due to bandwidth limitations. Conventional machine learning methods are not designed for this type of data distribution. Experts mark a training data set with different levels of saliency emphasizing speed rather than accuracy due to the size of the task. The challenge is to develop machine learning methods that learn how the expert has marked the training data so that similar test data sets can be marked more efficiently. Ensembles of machine learning classifiers are typically more accurate than individual classifiers. An ensemble of machine learning classifiers requires substantially less memory than the corresponding partition of the data set. This allows the transfer of ensembles among partitions. If all the ensembles are sent to each partition, they can vote for a level of saliency for each example in the partition. Different partitions of the data set may not have any salient points, especially if the data set has a time step dimension. This means the learned classifier for such partitions can not vote for saliency since they have not been trained to recognize it. In this work, we investigate the performance of different ensembles of classifiers on spatially partitioned data sets. Success is measured by the correct recognition of unknown and salient regions of data points.

Detecting data race is very important for debugging shared-memory parallel programs, because data races result in unintended nondeterministic execution of the program. We propose a dynamic on-the-fly race detection mechanism called Parallel Nondeterminator to check for determinacy races during the parallel execution of a program with recursive spawn-sync parallelism. A modified version of Nested Region Labeling scheme is developed for the concurrency relationship test in the spawn-sync parallel structure. Through the identification of Least Common Ancestor in the spawn tree, the Parallel Nondeterminator only needs to keep two read access records and one write access record for each shared location. The work and critical path in the instrumented codes are analyzed as well as time complexity and space requirements. Let N denote the maximum depth of the recursion in the parallel program. The worst case time increased for each spawn and sync operation is O(N) and the time required to monitor any shared memory location is O(lgN). Moreover, Parallel Nondeterminator is able to execute the race detection code without loss of parallelism of the original program. In summary, the Parallel Non-determinator represents a provably efficient strategy for detecting data races for shared-memory parallel programs. / Singapore-MIT Alliance (SMA)

In this thesis, a Content Based Image Retrieval (CBIR) system to query the objects in an image database is proposed. Images are represented as collections of regions after being segmented with Normalized Cuts algorithm. MPEG-7 content descriptors are used to encode regions in a 239-dimensional feature space. User of the proposed CBIR system decides which objects to query and labels exemplar regions to train the system using a graphical interface. Fuzzy ARTMAP algorithm is used to learn the mapping between feature vectors and binary coded class identification numbers. Preliminary recognition experiments prove the power of fuzzy ARTMAP as a region classifier. After training, features of all regions in the database are extracted and classified. Simple index files enabling fast access to all regions from a given class are prepared to be used in the querying phase. To retrieve images containing a particular object, user opens an image and selects a query region together with a label in the graphical interface of our system. Then the system ranks all regions in the indexed set of the query class with respect to their L2 (Euclidean) distance to the query region and displays resulting images. During retrieval experiments, comparable class precisions with respect to exhaustive searching of the database are maintained which demonstrates e ectiveness of the classifier in narrowing down the search space.