Matthew L. Seidl

Segregating heap objects by reference behavior and lifetime

Dynamic storage allocation has become increasingly important in many applications, in part due to the use of the object-oriented paradigm. At the same time, processor speeds are increasing faster than memory speeds and programs are increasing in size faster than memories. In this paper, we investigate efforts to predict heap object reference and lifetime behavior at the time objects are allocated. Our approach uses profile-based optimization, and considers a variety of different information sources present at the time of object allocation to predict the objects reference frequency and lifetime. Our results, based on measurements of six allocation intensive programs, show that program references to heap objects are highly predictable and that our prediction methods can successfully predict the behavior of these heap objects. We show that our methods can decrease the page fault rate of the programs measured, sometimes dramatically, in cases where the physical memory available to the program is constrained.

Generic web-based teleoperations architecture: details and experience

Teleoperation of remote devices on the World Wide Web is becoming more common and feasible. Prices on devices ranging from digital cameras to LEGO RCXs(tm) have dropped, making them available to a much wider audience. Increasing availability of remotely operable devices removes one barrier to ubiquitous telepresence, but leaves others intact. One of the remaining barriers is the need for a user to develop and deploy an end-to-end solution for device manipulation. The goal of our research is to reduce this barrier by making a flexible end-to-end solution accessible to a wide audience of potential Web device developers.

Programmable ubiquitous telerobotic devices

We are investigating a field of research that we call ubiquitous telepresence, which involves the design and implementation of low-cost robotic devices that can be programmed and operated from anywhere on the Internet. These devices, which we call ubots, can be used for academic purposes (e.g., a biologist could remote conduct a population survey), commercial purposes (e.g., a house could be shown remotely by a real-estate agent), and for recreation and education (e.g., someone could tour a museum remotely). We anticipate that such devices will become increasingly common due to recent changes in hardware and software technology. In particular, current hardware technology enables such devices to be constructed very cheaply (less than

Implementing heap-object behavior prediction efficiently and effectively: PREDICTING HEAP-OBJECT BEHAVIOR

500), and current software and network technology allows highly portable code to be written and downloaded across the Internet. In this paper, we present our prototype system architecture, and the ubot implementation we have constructed based on it. The hardware technology we use is the handy board, a 6811-based controller board with digital and analog inputs and outputs. Our software includes a network layer based on TCP/IP and software layers written in Java. Our software enables users across the Internet to program the behavior of the vehicle and to receive image feedback from a camera mounted on it.

Wireless communications with mobile devices in a web-based teleoperations environment

Heap‐allocated objects play an important role in many modern programs. Various results have shown the overall performance of these programs can be improved by increasing the reference locality of heap‐allocated objects. In this paper we describe an approach that improves the virtual memory performance of allocation‐intensive C programs by predicting the reference behavior and lifetime of heap objects as they are allocated. We further describe an implementation of our prediction algorithm and evaluate its performance on real programs. As part of our implementation, we present a low‐overhead algorithm to minimize the cost of gathering run‐time stack information. Finally, we show that an implementation of these algorithms has little overhead and can improve the virtual memory and TLB performance of programs substantially. Copyright

Reusable framework for Web-based teleoperation

Deploying robotic devices for Web-based teleoperation is currently the domain of academic researchers, commercial enterprises and a small group of dedicated hobbyists. Before more people can deploy their own devices, a number of difficult issues need to be addressed. In previous work, we presented a reusable framework for Web-based teleoperation of robotic devices and attempted to address some of these deployment issues. However, a number of problems still remain, including how to support communication with a mobile remote device. Any remotely operated device requires some form of communication channel to its operator. In many current systems, this communications channel is composed of a long-haul network connection as well as a short-range connection between the device and a base unit. For a mobile device, one traditional solution for this short-range connection has been tethered operation. Tethered operation imposes a number of undesirable limitations on mobile devices however, so many researchers have turned to wireless communication as an alternative. As both the monetary and power costs associated with wireless communications continue to decrease, it becomes more viable as a general solution to the problem of providing communication between a base unit and a mobile device. We present an overview of the current state of the art in commercially available wireless communications and its implications for Web-based teleoperations. We also discuss how the requirements and implementation of our existing reusable framework will be modi ed in response to the new requirements imposed by wireless communication.

Predicting References to Dynamically Allocated Objects

The advent of the WWW presents an opportunity for a wide audience to make use of telemanipulation. Unfortunately, current efforts in Web-based telemanipulation are primarily undertaken by individual groups and lead to a plethora of specific solutions, instead of a general, reusable framework. Because of this, any groups seeking to enter into this field must spend a large amount of time building the interfaces necessary for remote monitoring and manipulation. Our proposed solution to this problem is to build a general framework of Java-based components that allow researchers to focus on their particular applications instead of building the infrastructure for Web interaction themselves. These components only require researchers to build an interface to our framework, instead of implementing a complete end-to-end solutions. This framework is designed to enable the manipulation of simple to medium complexity devices via the WWW. Example application domains include small robotic vehicles and robotic arms.