Modeling flow information of loops using compositional condition of controls

Parsa, Saeed; Sakhaei-nia, Mehdi

doi:10.1007/s11227-014-1308-5

Cited by 3 publications

(3 citation statements)

References 25 publications

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“…; (2) Control-flow Analysis (or called high-level analysis), such as control-flow reconstruction [25,26], loop bound analysis [27,28], etc. ; (3) WCET Calculating, using integral linear programming (ILP) to compute a final result.…”

Section: Reasons For Wcet Overestimationmentioning

confidence: 99%

Reducing WCET Overestimations by Correcting Errors in Loop Bound Constraints

Meng

2017

Energies

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Abstract:In order to reduce overestimations of worst-case execution time (WCET), in this article, we firstly report a kind of specific WCET overestimation caused by non-orthogonal nested loops. Then, we propose a novel correction approach which has three basic steps. The first step is to locate the worst-case execution path (WCEP) in the control flow graph and then map it onto source code. The second step is to identify non-orthogonal nested loops from the WCEP by means of an abstract syntax tree. The last step is to recursively calculate the WCET errors caused by the loose loop bound constraints, and then subtract the total errors from the overestimations. The novelty lies in the fact that the WCET correction is only conducted on the non-branching part of WCEP, thus avoiding potential safety risks caused by possible WCEP switches. Experimental results show that our approach reduces the specific WCET overestimation by an average of more than 82%, and 100% of corrected WCET is no less than the actual WCET. Thus, our approach is not only effective but also safe. It will help developers to design energy-efficient and safe real-time systems.

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Section: Reasons For Wcet Overestimationmentioning

confidence: 99%

Reducing WCET Overestimations by Correcting Errors in Loop Bound Constraints

Meng

2017

Energies

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“…The value of a branch condition depends on the value of its constituents at the program point where the branch condition is located. To eliminate the dependencies, all the branch conditions are expressed in terms of the variables whose values are not defined along the subpath of the execution path, from the loop entry point up to the point where the branch condition is located [13]. Therefore, the path constraint stratification is performed base on the program state at the entry point of the loop.…”

Section: Symbolic Flow Analysismentioning

confidence: 99%

“…The operations include those statements that directly or indirectly affect the value of the loop. Applying a data flow analysis, all the statements affecting the loop variable are located [13].…”

Section: Pc(execution-path Ep)mentioning

confidence: 99%

PLEA: Parametric loop bound estimation in WCET analysis

Parsa¹,

Sakhaei-nia²

2016

Turk J Elec Eng & Comp Sci

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Worst-case execution time (WCET) analysis of a program is important to verify the temporal correctness of real-time systems. Parametric WCET analysis represents the WCET of the program as a formula, where the unknown values affecting the WCET are parameterized. Many issues usually affect the WCET of a program, including the loop bound. In parametric timing analysis, instead of determining a constant upper bound for a loop, a symbolic formula represents the loop bound. In this paper, a new method is presented for the parametric loop bound analysis based on path analysis. Instead of considering the basic bocks on their own and independent of the rest, the execution paths within the loop body have to be analyzed. There are certain situations in which the execution of certain statements of an execution path affects the number of executions of all the basic blocks along the execution path. Therefore, more accurate estimation of the number of loop iterations is provided. The results of analysis on the Mälardalen benchmark suite reveal the accuracy of the proposed method.

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Interactive WCET Prediction with Warning for Timeout Risk

Meng

2017

Int. J. Patt. Recogn. Artif. Intell.

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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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Modeling flow information of loops using compositional condition of controls

Cited by 3 publications

References 25 publications

Reducing WCET Overestimations by Correcting Errors in Loop Bound Constraints

Reducing WCET Overestimations by Correcting Errors in Loop Bound Constraints

PLEA: Parametric loop bound estimation in WCET analysis

Interactive WCET Prediction with Warning for Timeout Risk

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