Yasuichi Nakayama

A new memory allocation method for shared memory multiprocessors with large virtual address space

This paper proposes a new memory allocation method for shared memory multiprocessors with large virtual address spaces. An evaluation of its performance is also presented. For effective use of shared memory multiprocessors, it is important that no processors execution is blocked. If several processors simultaneously access a shared variable, their processes are blocked and access to the variable is serialized. Thus, frequent access to shared variables reduces the parallelism. In particular, the parallelism is significantly reduced when a special shared variable – the ‘allocation pointer’ – is frequently accessed in the dynamic object allocation by an application program. In this paper, we propose a new method for allocating physical memory pages where the allocation pointer is monotonically increased in the virtual address space in contrast to the conventional method. This allows the critical sections for access to the allocation pointer to be executed effectively and atomically by using the fetch-and-add primitive. Our method improves the application programs parallelism by access to the allocation pointer with considerably short blocking time to the process.

Analysis and measurement of the effect of kernel locks in SMP systems

This article reports the use of case studies to evaluate the performance degradation caused by the kernel‐level lock. We define the lock ratio as a ratio of the execution time for critical sections to the total execution time of a parallel program. The kernel‐level lock ratio determines how effective programs work on symmetric multiprocessor (SMP) systems. We have measured the lock ratios and the performance of three types of parallel programs on SMP systems with Linux 2.0: matrix multiplication, parallel make, and WWW server programs. Experimental results show that the higher the lock ratio of parallel programs, the worse their performance becomes. Copyright

Secure and high-performance Web server system for shared hosting service

We developed Hi-sap, a Web server system that ensures the security in a server and has high performance when processing dynamic content. In existing servers, server embedded programs cannot be used safely in large-scale environments like a shared hosting service. These problems occur because server processes run under the privilege of an identical user. For example, server embedded interpreters are commonly used to improve performance in processing dynamic content, like Weblogs and wikis. However, other customers that share the same server can steal, delete, and tamper with data files of Weblogs and wikis. To solve these problems, we designed a new Web server system, Hi-sap. In the system, Web objects that are stored in a server are divided into partitions. Server processes run under the privilege of different users in every partition. We implemented Hi-sap on a Linux OS and tested the effectiveness of the system. Experimental results show that Hi-sap has high performance and scalability

Trial of Learning Support System Using Kinect in After School Care Programs

The important roles of after school care programs are protecting the lives of students whose parents are working or unable to be at home after they finish school or on school holidays and helping them create self independence. We propose a learning support system for helping after school care students. The system is used for practicing the “Kuku” multiplication table and it has been implemented using the Kinect motion capture system to recognize “air characters” written by the body actions of learners. We conducted a trial to evaluate the proposed system by asking many students in after school care programs to participate and confirmed that this system was helpful for groups of students to learn. We explain here how we implemented the system, and report the results from the trial. We also suggest the future directions of the system.

Lesser Bear—a light‐weight process library for SMP computers

We have designed and implemented a light‐weight process (thread) library called ‘Lesser Bear’ for SMP computers. Lesser Bear has high portability and thread‐level parallelism. Creating UNIX processes as virtual processors and a memory‐mapped file as a huge shared‐memory space enables Lesser Bear to execute threads in parallel. Lesser Bear requires exclusive operation between peer virtual processors, and treats a shared‐memory space as a critical section for synchronization of threads. Therefore, thread functions of the previous Lesser Bear are serialized. In this paper, we present a scheduling mechanism to execute thread functions in parallel. In the design of the proposed mechanism, we divide the entire shared‐memory space into partial spaces for virtual processors, and prepare two queues (Protect Queue and Waiver Queue) for each partial space. We adopt an algorithm in which lock operations are not necessary for enqueueing. This algorithm allows us to propose a scheduling mechanism that can reduce the scheduling overhead. The mechanism is applied to Lesser Bear and evaluated by experimental results. Copyright

A learning support system for 9 × 9 multiplication table with Kinect

We propose a learning support system for the 9 × 9 multiplication table “KuKu” and have implemented it using Kinect motion capture to recognize “air characters” written by the body actions of KuKu learners. We explain how to implement the system, report the results of a trial with elementary school students, and suggest the future directions of the system.

A PC cluster system employing IEEE 1394

In this paper, we describe the design and evaluation of a PC cluster system in which IEEE 1394 is applied. Networks for parallel cluster computing require low latency and high bandwidth. It is also important that the networks be commercially available at low cost. Few network devices satisfy all of the above requirements. However, the IEEE 1394 standard provides a good compromise for fulfilling these requirements. We have used IEEE 1394 devices, which support a 400 Mbps data transfer rate, to connect the nodes of a PC cluster system which we have designed and implemented. We have implemented two communication libraries. One is a fast communication library called CF for IEEE 1394. The other is a MPI layer library on the CF library. Experimental results show that CF achieves a 17.2 microsecond round‐trip time. On application benchmarks, the system was considerably faster than TCP/IP over Fast Ethernet. Even though the system was constructed at very low cost, it provides good performance. Using the IEEE 1394 standard is thus a good solution for low‐cost cluster systems. Copyright

A playing and learning support system using Kinect for Romaji

The use of information devices in educational settings has been increasing over the years. We propose a learning support system that is an expansion of the original Kinect system. The proposed expansion has been implemented using the Kinect motion capture system to recognize “air characters” written by the body actions of learners and is used in this study for practicing Japanese letters expressed in Romaji by a combination of alphabets. We believe that students can have fun with learning by performing body actions, thus keeping their motivation to learn high. We had some elementary school students operate the system and then evaluated the results.

Geometric alignment for large point cloud pairs using sparse overlap areas

We present a novel approach for geometric alignment of 3D sensor data. The Iterative Closest Point (ICP) algorithm is widely used for geometric alignment of 3D models as a point-to-point matching method when an initial estimate of the relative pose is known. However, the accuracy of the correspondence between point and point is difficult when the points are sparsely distributed. In addition, the searching cost is high because the ICP algorithm requires a search of the nearest-neighbor points at every minimization. In this paper, we describe a plane-to-plane registration method. We define the distance between two planes and estimate the translation parameter by minimizing the distance between the planes. The plane-to-plane method is able to register the set of scatter points which are sparsely distributed and the density is low with low cost. We tested this method with the large scatter points of a manufacturing plant and show the effectiveness of our proposed method.

Reconstruction of 3D Indoor Model by Scalable Sensing Using Mobile Robot

To construct a 3D model of an environment with minimal information loss, integrated sensor data from many viewpoints are needed. However, this increases the amount of useless data, and it also takes too much time. Based on this problem, we developed a scalable sensing scheme using a robot system to reconstruct indoor environments. We mounted a freely rotating range sensor on a mobile robot to acquire range data in a real office environment, and we constructed a 3D model of that environment. The scheme determines the frequency of the measurement in each direction according to the complexity of the shape. If the shape on the direction of the sensors angle is simple, the frequency of the measurement becomes low. On the other hand, if the shape is compleex, the frequency is high. It also does not acquire data in areas that have alreaedy been measured. The results showed that a 3D model can be constructed with less frequent measurements with our scheme.