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Interactive WCET Prediction with Warning for Timeout Risk

International Journal of Pattern Recognition and Artificial Intelligence

November 2016
31(05)

Authors:

Worst case execution time (WCET) analysis is essential for exposing timeliness defects when developing hard real-time systems. However, it is too late to fix timeliness defects cheaply since developers generally perform WCET analysis in a final verification phase. To help developers quickly identify real timeliness defects in an early programming phase, a novel interactive WCET prediction with warning for timeout risk is proposed. The novelty is that the approach not only fast estimates WCET based on a control flow tree (CFT), but also assesses the estimated WCET with a trusted level by a lightweight false path analysis. According to the trusted levels, corresponding warnings will be triggered once the estimated WCET exceeds a preset safe threshold. Hence developers can identify real timeliness defects more timely and efficiently. To this end, we first analyze the reasons of the overestimation of CFT-based WCET calculation; then we propose a trusted level model of timeout risks; for recognizing the structural patterns of timeout risks, we develop a risk data counting algorithm; and we also give some tactics for applying our approach more effectively. Experimental results show that our approach has almost the same running speed compared with the fast and interactive WCET analysis, but it saves more time in identifying real timeliness defects.

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Interactive WCET Prediction with Warning

for Timeout Risk

Fanqi Meng

†

‡

, Xiaohong Su

and Zhaoyang Qu

†

,¶

School of Computer Science and Technology

Harbin Institute of Technology, Harbin 150001, P. R. China

†

School of Information Engineering

Northeast Dianli University, Jilin 132012, P. R. China

‡

mengfanqi@nedu.edu.cn

sxh@hit.edu.cn

quzhaoyang@nedu.edu.cn

Received 8 August 2016

Accepted 19 September 2016

Published 30 November 2016

Worst case execution time (WCET) analysis is essential for exposing timeliness defects when

developing hard real-time systems. However, it is too late to ¯x timeliness defects cheaply since

developers generally perform WCET analysis in a ¯nal veri¯cation phase. To help developers

quickly identify real timeliness defects in an early programming phase, a novel interactive

WCET prediction with warning for timeout risk is proposed. The novelty is that the approach

not only fast estimates WCET based on a control °ow tree (CFT), but also assesses the

estimated WCET with a trusted level by a lightweight false path analysis. According to the

trusted levels, corresponding warnings will be triggered once the estimated WCET exceeds a

preset safe threshold. Hence developers can identify real timeliness defects more timely and

e±ciently. To this end, we ¯rst analyze the reasons of the overestimation of CFT-based WCET

calculation; then we propose a trusted level model of timeout risks; for recognizing the structural

patterns of timeout risks, we develop a risk data counting algorithm; and we also give some

tactics for applying our approach more e®ectively. Experimental results show that our approach

has almost the same running speed compared with the fast and interactive WCET analysis, but

it saves more time in identifying real timeliness defects.

Keywords: Pattern recognition; software safety; interactive WCET analysis; risk warning;

embedded Java.

1. Introduction

Worst case execution time (WCET) is an important issue in the research ¯eld of real-

time systems because it is a key parameter to both the schedulability analysis of

tasks

14,36,53–

and the safety validation of software.

11,20,28

With the development of

Corresponding author.

International Journal of Pattern Recognition

and Arti¯cial Intelligence

Vol. 31, No. 5 (2017) 1750012 (24 pages)

cWorld Scienti¯c Publishing Company

DOI: 10.1142/S0218001417500124

1750012-1

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\ge

80 %, cosine similarity is

\ge

99.5 % and max quotient between corresponding items is

\le

50, the average error of NL-WCET is merely 0.82 %, quite lower than conventional WCET measurement. Meanwhile it also has higher efficiency than conventional WCET analysis. Thus NL-WCET is suitable for being used during programming phase, and can help programmers to discover timeliness defects as early as possible.

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