arXiv subjects

Vladimir Kovalenko

Publications and source records attributed to Vladimir Kovalenko.

34 records · Page 2Linked to original sources

arXiv2020

Pandemic Programming: How COVID-19 affects software developers and how their organizations can help

Context. As a novel coronavirus swept the world in early 2020, thousands of software developers began working from home. Many did so on short notice, under difficult and stressful conditions. Objective. This study investigates the effects of the pandemic on developers' wellbeing and productivity. Method. A questionnaire survey was created mainly from existing, validated scales and translated into 12 languages. The data was analyzed using non-parametric inferential statistics and structural equation modeling. Results. The questionnaire received 2225 usable responses from 53 countries. Factor analysis supported the validity of the scales and the structural model achieved a good fit (CFI = 0.961, RMSEA = 0.051, SRMR = 0.067). Confirmatory results include: (1) the pandemic has had a negative effect on developers' wellbeing and productivity; (2) productivity and wellbeing are closely related; (3) disaster preparedness, fear related to the pandemic and home office ergonomics all affect wellbeing or productivity. Exploratory analysis suggests that: (1) women, parents and people with disabilities may be disproportionately affected; (2) different people need different kinds of support. Conclusions. To improve employee productivity, software companies should focus on maximizing employee wellbeing and improving the ergonomics of employees' home offices. Women, parents and disabled persons may require extra support.

cs.SE↗

arXiv2020

Sosed: a tool for finding similar software projects

In this paper, we present Sosed, a tool for discovering similar software projects. We use fastText to compute the embeddings of subtokens into a dense space for 120,000 GitHub repositories in 200 languages. Then, we cluster embeddings to identify groups of semantically similar sub-tokens that reflect topics in source code. We use a dataset of 9 million GitHub projects as a reference search base. To identify similar projects, we compare the distributions of clusters among their sub-tokens. The tool receives an arbitrary project as input, extracts sub-tokens in 16 most popular programming languages, computes cluster distribution, and finds projects with the closest distribution in the search base. We labeled subtoken clusters with short descriptions to enable Sosed to produce interpretable output. Sosed is available at https://github.com/JetBrains-Research/sosed/. The tool demo is available at https://www.youtube.com/watch?v=LYLkztCGRt8. The multi-language extractor of sub-tokens is available separately at https://github.com/JetBrains-Research/buckwheat/.

cs.SE↗

arXiv2020

Using Large-Scale Anomaly Detection on Code to Improve Kotlin Compiler

In this work, we apply anomaly detection to source code and bytecode to facilitate the development of a programming language and its compiler. We define anomaly as a code fragment that is different from typical code written in a particular programming language. Identifying such code fragments is beneficial to both language developers and end users, since anomalies may indicate potential issues with the compiler or with runtime performance. Moreover, anomalies could correspond to problems in language design. For this study, we choose Kotlin as the target programming language. We outline and discuss approaches to obtaining vector representations of source code and bytecode and to the detection of anomalies across vectorized code snippets. The paper presents a method that aims to detect two types of anomalies: syntax tree anomalies and so-called compiler-induced anomalies that arise only in the compiled bytecode. We describe several experiments that employ different combinations of vectorization and anomaly detection techniques and discuss types of detected anomalies and their usefulness for language developers. We demonstrate that the extracted anomalies and the underlying extraction technique provide additional value for language development.

cs.SE↗

arXiv2020

Building Implicit Vector Representations of Individual Coding Style

With the goal of facilitating team collaboration, we propose a new approach to building vector representations of individual developers by capturing their individual contribution style, or coding style. Such representations can find use in the next generation of software development team collaboration tools, for example by enabling the tools to track knowledge transfer in teams. The key idea of our approach is to avoid using explicitly defined metrics of coding style and instead build the representations through training a model for authorship recognition and extracting the representations of individual developers from the trained model. By empirically evaluating the output of our approach, we find that implicitly built individual representations reflect some properties of team structure: developers who report learning from each other are represented closer to each other.

cs.SE↗

arXiv2019

Determination of the quark-gluon string parameters from the data on pp, pA and AA collisions at wide energy range using Bayesian Gaussian Process Optimization

Bayesian Gaussian Process Optimization can be considered as a method of the determination of the model parameters, based on the experimental data. In the range of soft QCD physics, the processes of hadron and nuclear interactions require using phenomenological models containing many parameters. In order to minimize the computation time, the model predictions can be parameterized using Gaussian Process regression, and then provide the input to the Bayesian Optimization. In this paper, the Bayesian Gaussian Process Optimization has been applied to the Monte Carlo model with string fusion. The parameters of the model are determined using experimental data on multiplicity and cross section of pp, pA and AA collisions at wide energy range. The results provide important constraints on the transverse radius of the quark-gluon string ($r_{str}$) and the mean multiplicity per rapidity from one string ($μ_0$).

physics.data-an↗

arXiv2019

Strongly intensive fluctuations and correlations in ultrarelativistic nuclear collisions in the model with string fusion

The several types of strongly intensive correlation variables are studied in nuclear collisions at LHC energy. These quantities are expected not to depend on centrality class width. They have been calculated in the dipole-based parton-string Monte Carlo model with string fusion. The centrality dependence of the mean transverse momentum correlation coefficient and strongly intensive quantity $Σ$ between multiplicity and $P_T$ have been obtained. Dynamical charge fluctuation $ν_{dyn}$ has been also calculated and compared with experimental data. It is shown that string fusion improves agreement with the experiment.

nucl-th↗

arXiv2017

Correlation between heavy flavour production and multiplicity in pp and p-Pb collisions at high energy in the multi-pomeron exchange model

The multiplicity dependence of heavy flavour production in pp-collisions at LHC energies is studied in the framework of the multi-pomeron exchange model. The model is introducing the string-string interaction collectivity effects in pp collisions, which modifies multiplicity and transverse momenta, leading to the non-trivial mean pt vs. multiplicity ( _Nch - Nch) correlation. The string collectivity strength parameter is fixed by experimental data on multiplicity and transverse momentum correlation in a wide energy range (from ISR to LHC). The particles discrimination is implemented according to Schwinger mechanism taking into account the strong decays of hadron resonances. We demonstrate, that the faster-than-linear growth of the open charm production with the event charged particle multiplicity, observed in experimental pp high energy collisions, can be explained by the modification of the string tension due to the increasing overlap and interaction of quark-gluon strings. The model is extended for p-A interactions and the calculations for p-Pb collisions are performed.

nucl-th↗

arXiv2016

Classifiers for centrality determination in proton-nucleus and nucleus-nucleus collisions

Centrality, as a geometrical property of the collision, is crucial for the physical interpretation of nucleus-nucleus and proton-nucleus experimental data. However, it cannot be directly accessed in event-by-event data analysis. Common methods for centrality estimation in A-A and p-A collisions usually rely on a single detector (either on the signal in zero-degree calorimeters or on the multiplicity in some semi-central rapidity range). In the present work, we made an attempt to develop an approach for centrality determination that is based on machine-learning techniques and utilizes information from several detector subsystems simultaneously. Different event classifiers are suggested and evaluated for their selectivity power in terms of the number of nucleons-participants and the impact parameter of the collision. Finer centrality resolution may allow to reduce impact from so-called volume fluctuations on physical observables being studied in heavy-ion experiments like ALICE at the LHC and fixed target experiment NA61/SHINE on SPS.

physics.data-an↗

arXiv2016

Forward-backward correlations between intensive observables

We demonstrate that the investigations of the forward-backward correlations between intensive observables enable to obtain more clear signal about the initial stage of hadronic interaction, e.g. about the process of string fusion, compared to usual forward-backward multiplicity correlations. As an example, the correlation between mean-event transverse momenta of charged particles in separated rapidity intervals is considered. We performed calculations in the framework of dipole-based Monte Carlo string fusion model. We obtained the dependence of the correlation strength on the collision centrality for different initial energies and colliding systems. It is shown that the dependence reveals the decline of the correlation coefficient for most central Pb-Pb collisions at LHC energy. We compare the results both with the ones obtained in alternative models and with the ones obtained by us using various MC generators.

nucl-th↗

arXiv2015

Strangeness production and long-range correlations in pp collisions in string fusion approach

The effects of string fusion on the correlations in strange particles production in proton-proton collisions at high energy are studied in the framework of a Monte Carlo string-parton model. The model is based on the strings formation in elementary dipole-dipole collisions. The hardness of the elementary interaction is defined by a transverse size of the colliding dipoles. The interaction between strings is realized in the accordance with the string fusion model prescriptions by the introduction of the lattice in the impact parameter plane and taking into account the finite rapidity length of strings. The particles species differentiation is implemented according to Schwinger mechanism. The parameters of the model are fixed with the experimental data on total inelastic cross section and charged multiplicity. In the framework of the model the long-range correlation functions with an accounting of strangeness have been studied. A new intensive event-by-event observable has been proposed, which characterizes the fraction of strange particles in the event. The predictions on the correlations between strangeness, multiplicity and mean transverse momentum are obtained for pp collisions at 7 TeV.

hep-ph↗

arXiv2015

Long-range correlation studies at the SPS energies in MC model with string fusion

Studies of the ultrarelativistic collisions of hadrons and nuclei at different centrality and energy enable to explore the QCD phase diagram in a wide range of temperature and baryon density. Long-range correlation studies are considered as a tool, sensitive to the observation of phase transition and the critical point. In the present work, a Monte Carlo model of proton-proton, proton-nucleus, and nucleus-nucleus collisions is applied to heavy and light ion collisions at the cms energy range from a few up to several hundred GeV per nucleon. The model describes the nuclear collisions at the partonic level through interaction of color dipoles and takes into account the effects of string fusion, which can be considered as an alternative to relativistic hydrodynamics way of describing the collective phenomena in heavy-ion collisions. The implementing of both the string fusion and the finite rapidity length of strings allowed to consider the particle production at non-zero baryochemical potential. We calculated the long-range correlation functions and correlation coefficients between multiplicities and transverse momentum at several energies for different colliding systems and obtained predictions for the experiment.

nucl-th↗

arXiv2014

Forward-backward multiplicity correlations in pp collisions at high energy in Monte Carlo model with string fusion

The correlations between multiplicities in two separated rapidity windows, is studied in the framework of the Monte Carlo model based on the picture of string formation in elementary collisions of colour dipoles. The hardness of the elementary collisions is defined by a transverse size of the interacting dipoles. The dependencies of the forward-backward correlation strength on the width and position of the pseudorapidity windows, as well as on transverse momentum range of observed particles were studied. It is demonstrated that taking into account of the string fusion effects improves the agreement with the available experimental data.

hep-ph↗

arXiv2014

Long-range correlations in proton-nucleus collisions in MC model with string fusion

The study of long-range correlations between observables in two rapidity windows was proposed as a signature of the string fusion and percolation phenomenon. In the present work we calculate the correlation functions and coefficients for p-Pb collisions in the framework of the Monte Carlo string-parton model, based on the picture of elementary collisions of color dipoles. It describes pA and AA scattering without referring to the Glauber picture of independent nucleons collisions and includes effects of string fusion. Different types of correlations are considered: n-n, pt-n, pt-pt, where n is the event multiplicity of charged particles in a given rapidity window and pt is their mean transverse momentum. The results, obtained in the present work for p-Pb collisions, are compared with available experimental results for pt-n correlations in one window and further predictions are made.

nucl-th↗

arXiv2013

Multi-pomeron exchange model for $pp$ and $p\bar{p}$ collisions at ultra-high energy

A new variant of the effective pomeron exchange model is proposed for the description of the correlation, observed in $pp$ and $p\bar{p}$ collisions at center-of-mass energy from SPS to LHC, between mean transverse momentum and charged particles multiplicity. The model is based on the Regge-Gribov approach. Smooth logarithmic growth with the collision energy was established for the parameter k, the mean rapidity density of charged particles produced by a single string. It was obtained in the model by the fitting of the available experimental data on charged particles rapidity density in $pp$ and $p\bar{p}$ collisions. The main effect of the model, a gradual onset of string collectivity with the growth of collision energy, is accounted by a free parameter β that is responsible in an effective way for the string fusion phenomenon. Another free parameter, t, is used to define string tension. We extract parameters β and t from the available experimental results on -multiplicity correlation at nucleon collision energy $\sqrt{s}$ from 17 GeV to 7 TeV. Smooth dependence of both β and t on energy allows to make predictions for the correlation behavior at the collision energy of 14 TeV. The indications to the string interaction effects in high multiplicity events in $pp$ collisions at the LHC energies are also discussed.

hep-ph↗

arXiv2013

Long-range rapidity correlations in high energy AA collisions in Monte Carlo model with string fusion

The magnitude of long-range correlations between observables in two separated rapidity windows, proposed as a signature of the string fusion and percolation phenomenon, is studied in the framework of non-Glauber Monte Carlo string-parton model, based on the picture of elementary collisions of color dipoles. The predictions, obtained with and without string fusion, demonstrate effects of color string fusion on the observables in Pb-Pb collisions at the LHC: decrease of n-n correlation coefficient with centrality and negative pt-n correlations, if the sufficiently effective centrality estimator is applied. In general case it is shown that the values of n-n and pt-n correlation coefficients strongly depend on the method of collision centrality fixation. In contrast, the predictions obtained for pt-pt correlation have almost no effect of centrality determination method and the corresponding experimental data would produce the strong limitation on the transverse radius of a string.

nucl-th↗

arXiv2012

Model of pp and AA collisions for the description of long-range correlations

Soft processes in pp and AA interactions are considered in the framework of phenomenological model with color strings formation and fusion. Elementary parton collisions are realized in the model as the interaction of two colour dipoles from projectile and target nucleons. Modeling of the exclusive distributions of parton momentum fractions and transverse coordinates is performed. The interaction of colour strings in transverse plane is carried out in the framework of local string fusion model with the introduction of the lattice in the impact parameter plane and taking into account the finite rapidity length of strings. The parameters were fixed with experimental data on pp total inelastic cross section and charged multiplicity. The model was used for the calculation of long-range correlations between the multiplicities (n) and the mean transverse momenta (pt) of charged particles. The dependence of n-n, pt-n, pt-pt correlations on the width and position of the backward and forward rapidity windows was studied. Note that the model enables to describe the AA interactions without referring to the Glauber picture based on the concept of elementary nucleon-nucleon collisions. In this connection the charged multiplicity, the mean numbers of participant nucleons and binary collisions and their variances in the case of PbPb collisions were calculated and compared with the predictions of alternative models and the experimental data. The influence of different ways of centrality determination on the multiplicity fluctuations and long-range correlations was also discussed.

nucl-th↗