3592511
An Array Data Flow Analysis Based Communication Optimizer
We present an efficient array data flow analysis based global communication optimizer which manages the analysis cost by partitioning the data flow problems into subproblems and solving the subproblems one at a time in a demand driven manner. In comparison to traditional array data flow based techniques, our scheme greatly reduces the memory requirement and manages the analysis time more effectively. The optimizer performs message vectorization, global redundant communication elimination and global communication scheduling. Our experience with the optimizer suggests that array data flow analysis for communication optimization is efficient and effective.
14857157
An MPI prototype for compiled communication on Ethernet switched clusters
Compiled communication has recently been proposed to improve communication performance for clusters of workstations. The idea of compiled communication is to apply more aggressive optimizations to communications whose information is known at compile time. Existing MPI libraries do not support compiled communication. In this paper, we present an MPI prototype, CC-MPI, that supports compiled communication on Ethernet switched clusters. The unique feature of CC-MPI is that it allows the user to manage network resources such as multicast groups directly and to optimize communications based on the availability of the communication information. CC-MPI optimizes one-to-all, one-to-many, all-to-all, and many-to-many collective communication routines using the compiled communication technique. We describe the techniques used in CC-MPI and report its performance.The results show that communication performance of Ethernet switched clusters can be significantly improved through compiled communication.
58764317
Performance of Multi-hop Communications Using Logical Topologies on Optical Torus Networks
We consider multi-hop communication in optical networks with time-division multiplexing. By using time-division multiplexing, multiple communication channels are supported on each link. As a result, more sophisticated logical topologies can be realized on top of a simpler physical network to improve the communication performance. These logical topologies reduce the number of intermediate hops that a packet travels at the cost of a larger multiplexing degree. On the one hand, the large multiplexing degree increases the packet communication time between hops. On the other hand, reducing the number of intermediate hops reduces the time spent at intermediate nodes. We study the trade-off between the multiplexing degree and the number of intermediate hops needed to realize the logical topologies on top of physical torus networks. Specifically, we examine four logical topologies ranging from the most complex logical all-to-all connections to the simplest logical torus topology. We develop an analytical model that models the maximum throughput and the average packet delay, verify the analytical model through simulations, and study the performance and the impact of system parameters on the performance for these logical topologies.
3570050
Algorithms for Supporting Compiled Communication
We investigate the compiler algorithms to support compiled communication in multiprocessor environments and study the benefits of compiled communication, assuming that the underlying network is an all-optical time-division-multiplexing (TDM) network. We present an experimental compiler, E-SUIF, that supports compiled communication for High Performance Fortran (HPF) like programs on all-optical TDM networks, and describe and evaluate the compiler algorithms used in E-SUIF. We further demonstrate the effectiveness of compiled communication on all-optical TDM networks by comparing the performance of compiled communication with that of a traditional communication method using a number of application programs.
8426908
Branch Elimination via Multi-variable Condition Merging
Conditional branches are expensive. Branches require a significant percentage of execution cycles since they occur frequently and cause pipeline flushes when mispredicted. In addition, branches result in forks in the control flow, which can prevent other code-improving transformations from being applied. In this paper we describe profile-based techniques for replacing the execution of a set of two or more branches with a single branch on a conventional scalar processor. First, we gather profile information to detect the frequently executed paths in a program. Second, we detect sets of conditions in frequently executed paths that can be merged into a single condition. Third, we estimate the benefit of merging each set of conditions. Finally, we restructure the control flow to merge the sets that are deemed beneficial. The results show that eliminating branches by merging conditions can significantly reduce the number of conditional branches performed in non-numerical applications.
7026270
Branch elimination by condition merging
Conditional branches are expensive. Branches require a significant percentage of execution cycles since they occur frequently and cause pipeline flushes when mispredicted. In addition, branches result in forks in the control flow, which can prevent other code-improving transformations from being applied. In this paper we describe profile-based techniques for replacing the execution of a set of two or more branches with a single branch on a conventional scalar processor. These sets of branches can include tests of multiple variables. For instance, the test if (p1 ! = 0 && p2 ! = 0), which is testing for NULL pointers, can be replaced with if (p1 & p2 ! = 0). Program profiling is performed to target condition merging along frequently executed paths. The results show that eliminating branches by merging conditions can significantly reduce the number of conditional branches executed in non-numerical applications.
223678
Automatic classification of digestive organs in wireless capsule endoscopy videos
Wireless Capsule Endoscopy (WCE) allows a physician to examine the entire small intestine without any surgical operation. With the miniaturization of wireless and camera technologies the ability comes to view the entire gestational track with little effort. Although WCE is a technical break-through that allows us to access the entire intestine without surgery, it is reported that a medical clinician spends one or two hours to assess a WCE video, It limits the number of examinations possible, and incur considerable amount of costs. To reduce the assessment time, it is critical to develop a technique to automatically discriminate digestive organs such as esophagus, stomach, small intestinal (i.e., duodenum, jejunum, and ileum) and colon. In this paper, we propose a novel technique to segment a WCE video into these anatomic parts based on color change pattern analysis. The basic idea is that the each digestive organ has different patterns of intestinal contractions that are quantified as the features. We present the experimental results that demonstrate the effectiveness of the proposed method.
1794602
HDR VolVis: high dynamic range volume visualization
In this paper, we present an interactive high dynamic range volume visualization framework (HDR VolVis) for visualizing volumetric data with both high spatial and intensity resolutions. Volumes with high dynamic range values require high precision computing during the rendering process to preserve data precision. Furthermore, it is desirable to render high resolution volumes with low opacity values to reveal detailed internal structures, which also requires high precision compositing. High precision rendering will result in a high precision intermediate image (also known as high dynamic range image). Simply rounding up pixel values to regular display scales will result in loss of computed details. Our method performs high precision compositing followed by dynamic tone mapping to preserve details on regular display devices. Rendering high precision volume data requires corresponding resolution in the transfer function. To assist the users in designing a high resolution transfer function on a limited resolution display device, we propose a novel transfer function specification interface with nonlinear magnification of the density range and logarithmic scaling of the color/opacity range. By leveraging modern commodity graphics hardware, multiresolution rendering techniques and out-of-core acceleration, our system can effectively produce an interactive visualization of large volume data, such as 2.048/sup 3/.
6706494
Real-Time Sensor Fusion Framework for Distributed Intelligent Sensors
Multi-sensor data fusion has found widespread applications in industrial and research sectors. The purpose of real time multi-sensor data fusion is to dynamically estimate an improved system model from a set of different data sources, i.e., sensors. This paper presented a systematic and unified real time sensor fusion framework (RTSFF) based on distributed intelligent sensor network. The RTSFF is an open architecture which consists of four layers – the transaction layer, the process fusion layer, the control layer, and the planning layer. This paradigm facilitates distribution of intelligence to the sensor level and sharing of information among sensors, controllers, and other devices in the system. The transducer layer is populated with intelligent sensors. The learning ability of the intelligent sensor model enables it to extract characteristics of monitored signal. The representation issue is managed at this level. After describing the RTSFF, the paper then focuses on the fundamental units of the framework, the highly autonomous transducers.
27055322
A Fast Evolution Strategies Based Approach To Image Registration
An image registration approach based on Evolution Strategies is proposed. In image registration, an invariant reference needs to be established within each source image, which is unavailable in many cases. To solve this problem, feature configuration (which is defined as the cluster of feature vectors on an image representing homogeneous feature distribution,) is employed to describe the object inside the scene. Instead of finding the correspondence of the entire image, the spatial relationships of the feature configuration in every source image are discovered with Evolution Strategies (ES). While one approach, even this one, may not be suitable for every image domain, the ES approach has many advantages. Compared to some methods, it is computationally effective; compared to other, it is capable of discovering transformations of larger scope (e.g., greater rotation angles or translation distances etc.) The search structure we use is an ellipsoid. The results from various images prove it to be an efficient and effective method.
2765235
Volumetric tongue reconstruction by fusing bidirectional MR images
In this paper we describe a 3D reconstruction method that fuses sagittal and coronal images. In our volumetric MRI study of the human tongue, multiple contiguous slices were acquired in the sagittal and the coronal planes. A bidirectional linear interpolation method was developed that estimated target voxel value using weighted neighbor pixels in the bounding slices. A wavelet fusion method was then employed to integrate prominent subband coefficients. Experiments have shown that fusion-based image reconstruction reduced artifacts, greatly improved reconstruction accuracy, and enhanced image details. Our method casts new light on MR imaging and image processing that demand high resolution in a short acquisition time