title: Identifying the interplay of design artifacts and decisions in practice: A Case Study

authors: Bowen, Judy

subjects: Science & Technology

abstract: Interaction design is a complex and challenging process. It encompasses skills and knowledge from design in general as well as from HCI and software design in particular. In order to find better ways to support interaction design and propose methods and tools to further the research in this area we must first better understand the nature of interaction design in practice. In this paper we present two small case studies which attempt to analyse design and decision-making through the lens of one particular theoretical framework. The framework seeks to focus design activities via its artifacts and the design spaces that exist in order to support reasoning about the process and the evolution of the artifacts. Our case studies show that we can use such a framework to consider real-world design projects, and also that there are further considerations that might usefully be included in such a framework.

text: Identifying the interplay of design artifacts and decisions in practice: A Case Study Interaction design is a complex and challenging process. It encompasses skills and knowledge from design in general as well as from HCI and software design in particular. In order to find better ways to support interaction design and propose methods and tools to further the research in this area we must first better understand the nature of interaction design in practice. In this paper we present two small case studies which attempt to analyse design and decision-making through the lens of one particular theoretical framework. The framework seeks to focus design activities via its artifacts and the design spaces that exist in order to support reasoning about the process and the evolution of the artifacts. Our case studies show that we can use such a framework to consider real-world design projects, and also that there are further considerations that might usefully be included in such a framework.

year: 2017

title: Controlling speculative execution through a virtually ordered memory system

authors: McWha, David J. A.

abstract: Processors which extract parallelism through speculative execution must be able to identify when mis-speculation has occurred. The three places where mis-speculation can occur are register accesses, control flow prediction and memory accesses. Controlling register and control flow speculation has been well studied, but no scalable techniques for identifying memory dependence violations have been identified. Since speculative execution occurs out of order this requires tracking the causal order, as well as the addresses of memory accesses. 

This thesis uses simulations to investigate tracking the causal order of memory accesses using explicit tags known as virtual timestamps, a distributed and scalable method. Realizable virtual timestamps are necessarily restricted in length and it is demonstrated that naive allocation schemes seriously constrain execution by inefficiently allocating virtual timestamps. Efficiently allocating virtual timestamps requires analysis of the number required by each section of code. Basic statically and dynamically evaluated analysis methods are established to avoid virtual timestamp allocation becoming a resource bottleneck.

The same analysis is also used to efficiently allocate state saving resources in a fixed hardware order. The hardware order provides an alternative way of maintaining the causal order using a simple hardware organization. The ability to predict the resources required by regions of code is used as a way of selecting instructions to execute speculatively. This enables resources to be allocated efficiently and is shown to allow large amounts of parallelism to be extracted. It also promotes the effectiveness of speculative execution by issuing less instructions that will ultimately be rolled back. 

Using a hierarchy of hardware ordering modules, themselves ordered by explicit virtual timestamps, a scalable ordering system is proposed. This hierarchy forms the basis of a twisted memory system, a multiple version memory system capable of identifying speculative memory dependence violations. The preliminary investigations presented here show that twisted memory has the potential to support aggressive speculative parallel execution. Particular attention is paid to memory bandwidth requirements.

text: Controlling speculative execution through a virtually ordered memory system Processors which extract parallelism through speculative execution must be able to identify when mis-speculation has occurred. The three places where mis-speculation can occur are register accesses, control flow prediction and memory accesses. Controlling register and control flow speculation has been well studied, but no scalable techniques for identifying memory dependence violations have been identified. Since speculative execution occurs out of order this requires tracking the causal order, as well as the addresses of memory accesses. 

This thesis uses simulations to investigate tracking the causal order of memory accesses using explicit tags known as virtual timestamps, a distributed and scalable method. Realizable virtual timestamps are necessarily restricted in length and it is demonstrated that naive allocation schemes seriously constrain execution by inefficiently allocating virtual timestamps. Efficiently allocating virtual timestamps requires analysis of the number required by each section of code. Basic statically and dynamically evaluated analysis methods are established to avoid virtual timestamp allocation becoming a resource bottleneck.

The same analysis is also used to efficiently allocate state saving resources in a fixed hardware order. The hardware order provides an alternative way of maintaining the causal order using a simple hardware organization. The ability to predict the resources required by regions of code is used as a way of selecting instructions to execute speculatively. This enables resources to be allocated efficiently and is shown to allow large amounts of parallelism to be extracted. It also promotes the effectiveness of speculative execution by issuing less instructions that will ultimately be rolled back. 

Using a hierarchy of hardware ordering modules, themselves ordered by explicit virtual timestamps, a scalable ordering system is proposed. This hierarchy forms the basis of a twisted memory system, a multiple version memory system capable of identifying speculative memory dependence violations. The preliminary investigations presented here show that twisted memory has the potential to support aggressive speculative parallel execution. Particular attention is paid to memory bandwidth requirements.

year: 2003

title: Tangi and final responsibilities

authors: Nikora, Linda Waimarie

abstract: Death is an ordinary everyday event in the Maori world. We have templated ways of responding to the disturbance it causes. This instructive and comforting institution helps us to hold each other close during such distressing times. In this address, Professor Linda Waimarie Nikora who co-leads the Tangi research programme at the University of Waikato, will critically reflect on the responsibilities incumbent upon the living to support, care and heal lives and spirits, living and newly departed.

text: Tangi and final responsibilities Death is an ordinary everyday event in the Maori world. We have templated ways of responding to the disturbance it causes. This instructive and comforting institution helps us to hold each other close during such distressing times. In this address, Professor Linda Waimarie Nikora who co-leads the Tangi research programme at the University of Waikato, will critically reflect on the responsibilities incumbent upon the living to support, care and heal lives and spirits, living and newly departed.

year: 2016