69 research outputs found
Mitigating the effect of coincidental correctness in spectrum based fault localization
2013 Summer.Includes bibliographical references.Coincidentally correct test cases are those that execute faulty program statements but do not result in failures. The presence of such test cases in a test suite reduces the effectiveness of spectrum-based fault localization approaches, such as Ochiai and Tarantula, which localize faulty statements by calculating a suspiciousness score for every program statement from test coverage information. The goal of this dissertation is to improve the understanding of how the presence of coincidentally correct test cases impacts the effectiveness of spectrum-based fault localization approaches and to develop a family of approaches that improve fault localization effectiveness by mitigating the effect of coincidentally correct test cases. Each approach (1)~classifies coincidentally correct test cases using test coverage information, and (2)~recalculates a suspiciousness score for every program statement using the classification information. We developed classification approaches using test coverage metrics at different levels of granularity, such as statement, branch, and function. We developed a new approach for ranking program statements using suspiciousness scores calculated based on the heuristic that the statements covered by more failing and coincidentally correct test cases are more suspicious. We extended the family of fault localization approaches to support multiple faults. We developed an approach to incorporate tester feedback to mitigate the effect of coincidental correctness. The approach analyzes tester feedback to determine a lower bound for the number of coincidentally correct test cases present in a test suite. The lower bound is also used to determine when classification of coincidentally correct test cases can improve fault localization effectiveness. We evaluated the fault localization effectiveness of our approaches and studied how the effectiveness changes for varying characteristics of test suites, such as size, test suite type (e.g., random, coverage adequate), and the percentage of passing test cases that are coincidentally correct. Our key findings are summarized as follows. Mitigating the effect of coincidentally correct test cases improved fault localization effectiveness. The extent of the improvement increased with an increase in the percentage of passing test cases that were coincidentally correct, although no improvement was observed when most passing test cases in a test suite were coincidentally correct. When random test suites were used to localize faults, a coarse-grained coverage spectrum, such as function coverage, resulted in better classification than fine-grained coverage spectra, such as statement and branch coverage. Utilizing tester feedback improved the precision of classification. Mitigating the effect of coincidental correctness in the presence of two faults improved the effectiveness for both faults simultaneously for most faulty programs. Faulty statements that were harder to reach and that affected fewer program statements resulted in fewer coincidentally correct test cases and were more effectively localized
Quantum dissipation and the virial theorem
In this note, we study the celebrated virial theorem for dissipative systems,
both classical and quantum. The classical formulation is discussed and an
intriguing effect of the random force (noise) is made explicit in the context
of the virial theorem. Subsequently, we derive a generalized virial theorem for
a dissipative quantum oscillator, i.e. a quantum oscillator coupled with a
quantum heat bath. Such a heat bath is modeled as an infinite collection of
independent quantum oscillators with a certain distribution of initial
conditions. In this situation, the non-Markovian nature of the quantum noise
leads to novel bath-induced terms in the virial theorem. We also consider the
case of an electrical circuit with thermal noise and analyze the role of
non-Markovian noise in the context of the virial theorem.Comment: v2: Revised version to appear in Physica
General structure of gauge boson propagator and its spectra in a hot magnetized medium
Based on transversality condition of gauge boson self-energy we have
systematically constructed the general structure of the gauge boson two-point
functions using four linearly independent basis tensors in presence of a
nontrivial background, i.e., hot magnetized material medium. The hard thermal
loop approximation has been used for the heat bath to compute various form
factors associated with the gauge boson's two point functions both in strong
and weak field approximation. We have also analyzed the dispersion of a gauge
boson (e.g., gluon) using the effective propagator both in strong and weak
magnetic field approximation. The formalism is also applicable to QED. The
presence of only thermal background leads to a longitudinal (plasmon) mode and
a two-fold degenerate transverse mode. In presence of a hot magnetized
background medium the degeneracy of the two transverse modes is lifted and one
gets three quasiparticle modes. In weak field approximation one gets two
transverse modes and one plasmon mode. On the other hand, in strong field
approximation also one gets the three modes in Lowest Landau Level. The general
structure of two-point function may be useful for computing the thermo-magnetic
correction of various quantities associated with a gauge boson.Comment: 39 pages, 7 figure
Inverse magnetic catalysis -- how much do we know about?
Some of the advances made in the literature to understand the phase
transitions of quark matter in the presence of strong magnetic field and finite
temperature (zero quark chemical potential) are reviewed. We start by
discussing the physics behind the Magnetic catalysis (MC) at zero/finite
temperature and then focus on the lattice predictions for inverse magnetic
catalysis (IMC) at high temperature and strong magnetic fields. Possible
explanations for the IMC are covered as well. Finally, we discuss recent
efforts to modify QCD (quantum chromodynamics) effective models in order to
reproduce the IMC observed on the lattice simulations. We emphasize the fact
that applying thermo-magnetic effects on the coupling constant of the NJL model
significantly improve the effectiveness of the NJL model to obtain a reasonable
physical description of hot and magnetized quark matter being in agreement with
lattice results.Comment: Invited mini-review submitted to EPJST. v2 improved few sentences
throughout the paper, added reference
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