• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.13-15
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• 2004

OpenMP 프로그램에서 수행되는 스레드들간에 적절한 동기화 없이 적어도 하나의 쓰기 사건으로 동일한 공유변수에 접근하는 경우에 발생되는 오류인 경합은 비결정적인 수행결과를 초래하므로 디버깅을 위해서 반드시 탐지되어야 한다. 이러한 경합탐지를 위한 기존의 디버깅 도구는 프로그램의 복잡한 수행구조 및 디버깅 정보를 시각화하기 위한 공간이 제한적이므로 효과적인 시각화를 제공하지 못한다. 본 논문에서는 경합 시각화를 위해서 3차원적 시각화와 스레드 및 이벤트 둥의 추상화 기능으로 공간적 제약성을 해결하는 도구를 제안한다. 제안된 도구는 추상적 시각화 정보를 제공하므로 프로그램의 이해가 용이하고 효과적인 경합디버깅 환경을 제공한다.

• The KIPS Transactions:PartA
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• v.17A no.1
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• pp.9-18
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• 2010

Races that occur in shared-memory parallel programs such as OpenMP programs must be detected for debugging because of causing unintended non-deterministic results. Previous works which verify the existence of these races on-the-fly are limited to the programs without internal non-determinism. But in the programs with internal non-determinism, such works need at least N! execution instances for each critical section to verify the existence of races, where N is the degree of maximum parallelism. This paper presents a preprocessor that statically analyzes the locations of non-deterministic accesses using program slicing and can detect apparent races as well as potential races through single execution using the analyzed information. The suggested tool can deterministically monitor non-deterministic accesses to occur in OpenMP programs so that this tool can verify the existence of races even if it is used any race detection protocol which can apply to programs with critical section. To prove empirically this tool, we have experimented using a set of benchmark programs such as synthetic programs that involve non-deterministic accesses, OpenMP Microbenchmark, NAS Parallel Benchmark, and OpenMP application programs.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.1_2
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• pp.41-50
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• 2004

Detecting races is important for debugging shared-memory Parallel programs, because races result in unintended nondeterministic executions of the programs. Particularly, the first races to occur in an execution of a program must be detected because they can potentially affect other races that occur later. Previous on-the-fly techniques that detect such first races based on candidate events that are likely to participate in the first races monitor access events in order to collect the candidate events during a program execution, and try to report the races only from determining the concurrency relationships of the candidates. Such races reported in this way. however, are not guaranteed to be first races, because they are not determined by taking into account how they are affected with each other. This paper presents a new post-mortem technique that analyzes, on each nesting level, candidate events collected from an execution of a shared-memory program with nested parallelism in order to report only first races. This technique is efficient, because it guarantees that first races reported by analyzing a nesting level are the races that occur first at the level, and does not require more analyses to the higher nesting levels than the current level. The Proposed technique facilitates more practical and effective debugging than the previous techniques, because it guarantees to detect first races if candidate events are collected from an execution instance of the program with nested parallelism.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.9
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• pp.395-406
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• 2007

Races in programs with OpenMP directives must be detected for debugging, because they may cause unexpected result by non-deterministic executions. But, Thread Checker of Intel corporation, a well-known existing tool for detecting the races, is not practical because this tool does not verify the existence of races and is known that the cost for race detection is too big. This paper presents a web-based tool which verify the existence of races with an optimal functionality and performance using the results from the property analysis of OpenMP program as well as the user requirements. Our tool is proved to be practical in the aspect of functionality and performance by experiments using synthetic programs, because the suggested tool can verify the existence of race and shows O(n) as the ratio of time consumption while Thread Checker can not verify the existence of race and shows $O(n^2)$ as the ratio, where n is the number of total accesses.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.7_8
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• pp.341-351
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• 2003

For debugging effectively the shared-memory programs with nested parallelism, it is important to detect efficiently the first races which incur non-deterministic executions of the programs. Previous on-the-fly technique detects the first races in two passes, and shows inefficiencies both in execution time and memory space because the size of an access history for each shared variable depends on the maximum parallelism of program. This paper proposes a new on-the-fly technique to detect the first races in two passes, which is constant in both the number of event comparisons and the space complexity on each access to shared variable because the size of an access history for each shared variable is a small constant. This technique therefore makes on-the-fly race detection more efficient and practical for debugging shared-memory programs with nested parallelism.

• Science of Emotion and Sensibility
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• v.16 no.3
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• pp.341-350
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• 2013

The present study aimed to understand the sensory characteristic of change detection by comparing the experience of detecting a salient visual change against the experience of detecting a sensory conflict evoked by a binocular mismatch. In Experiment 1, we used the change detection task where 2, 4, or 6 items were short-term remembered in visual working memory and were compared with following test items. The half of change-present trials were manipulated to elicit a binocular rivalry on the test item with the change by way of monocular inputs across the eyes. The results showed that change detection accuracy without the rivalry manipulation declined evidently as the display setsize increased whereas no such setsize effect was observed with the rivalry manipulation. Experiment 2 tested search efficiency for the search array where the target was designated as an item with the rivalry manipulation, and found the search was very efficient regardless of the rivalry manipulation. The results of Experiment 1 and 2 showed that when the given memory load varies, the experience of detecting a salient visual change become similar to the experience of detecting a sensory conflict by a binocular rivalry.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.07a
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• pp.1-2
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• 2016

다중 스레드 기반 병렬 프로그램에서의 자료경합 탐지는 동시에 수행되는 스레드 간의 비결정적인 상호작용 때문에 탐지하기 어려운 것으로 잘 알려져 있다. 동적 분석기술을 사용하여 자료경합을 탐지할 경우 프로그램 수행의 감시와 충돌하는 모든 메모리 연산의 분석을 위해 추가적인 오버헤드가 발생한다는 단점이 있다. 이러한 동적 분석의 추가적인 오버헤드를 줄이는 방법으로 감시 필터링 기술이 소개되고 있으며, 본 논문에서는 동적 자료경합 탐지를 위한 감시 필터링 기술 중 OpenMP 디렉티브 병렬 프로그램에 적용 가능한 두 기술을 대상으로 실용성과 효율성을 실험적으로 비교한다.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.884-894
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• 1999

순서적 동기화 및 내포 병렬성을 포함하는 공유메모리 병렬 프로그램에서의 경합(race)은 프로그램 수행에서 원하지 않은 비결정성(nondeterminism)을 야기할 수 있기 때문에 반드시 탐지되어져야 한다. 특히 프로그램 수행에서 최초경합(first race)을 탐지하는 것은 중요한데, 그 이유는 이 경합을 제거하면 다른 경합이 나타나지 않을 수도 있기 때문이다. 본 논문에서는 결정적 공유메모리 병렬프로그램을 위한 2단계 수행중 (two-pass on-the-fly) 최초경합 탐지 기법을 제시하며, 이것은 공유메모리 병렬 프로그램의 특정 수행에서 "최초로 발생되는" 경합들을 탐지하는 기법이다. 그리고 HPF 컴파일러를 이용하여 본 탐지 프로토콜을 공인된 벤치마크 프로그램에 적용하여, 병렬 프로그램 디버깅 시 고려하여야 할 파라미터들에 대한 실험으로부터 본 기법의 효율성을 보였다.Abstract Detecting races is important in debugging shared-memory parallel programs which have ordered synchronization and nested parallelism, because the races result in unintended non- deterministic executions of the programs. The first races are important in debugging, because the removal of such races may make other races disappear. It is even possible that all races reported would disappear once the first races are removed. This paper presents a new two-pass on-the-fly algorithm to detect the first races in such parallel programs. The algorithm reported in this paper is an on-the-fly algorithm that detects the races that "occur first" in a particular execution of shared-memory parallel programs. The experiment has accomplished, where two certified benchmark programs which can be executed under High Performance Fortran environments to get some parameters which improve debugging performance with our algorithm. with our algorithm.

• Korea Multimedia Society
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• v.7 no.3
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• pp.69-80
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• 2003

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.306-307
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• 2011

경합 상황, 교착 상태 등과 같은 동시 프로그램의 오류는 기존의 순차 프로그램에 적용되는 테스팅 방법으로는 탐지 및 재현이 힘들다. 하이젠버그라 불리는 이러한 오류는 프로그램의 안정성 및 신뢰성을 떨어뜨리는 원인이 될 수 있으므로 반드시 탐지하고 재현해야 한다. 본 논문은 SAT-solver와 경합 상태 탐지를 위한 Happens-before 알고리즘을 사용하여 ANSI-C 프로그램 내 존재하는 이러한 오류를 탐지하고 재현할 수 있는 방법을 제안한다.