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Documents authored by Peleg, Hila

Document
DOI: 10.4230/LIPIcs.ECOOP.2024.22
Constrictor: Immutability as a Design Concept

Authors: Elad Kinsbruner, Shachar Itzhaky, and Hila Peleg

Published in: LIPIcs, Volume 313, 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
Many object-oriented applications in algorithm design rely on objects never changing during their lifetime. This is often tackled by marking object references as read-only, e.g., using the const keyword in C++. In other languages like Python or Java where such a concept does not exist, programmers rely on best practices that are entirely unenforced. While reliance on best practices is obviously too permissive, const-checking is too restrictive: it is possible for a method to mutate the internal state while still satisfying the property we expect from an "immutable" object in this setting. We would therefore like to enforce the immutability of an object’s abstract state. We check an object’s immutability through a view of its abstract state: for instances of an immutable class, the view does not change when running any of the class’s methods, even if some of the internal state does change. If all methods of a class are verified as non-mutating, we can deem the entire class view-immutable. We present an SMT-based algorithm to check view-immutability, and implement it in our linter/verifier, Constrictor. We evaluate Constrictor on 51 examples of immutability-related design violations. Our evaluation shows that Constrictor is effective at catching a variety of prototypical design violations, and does so in seconds. We also explore Constrictor with two real-world case studies.
Cite as

Elad Kinsbruner, Shachar Itzhaky, and Hila Peleg. Constrictor: Immutability as a Design Concept. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 22:1-22:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{kinsbruner_et_al:LIPIcs.ECOOP.2024.22,
  author =	{Kinsbruner, Elad and Itzhaky, Shachar and Peleg, Hila},
  title =	{{Constrictor: Immutability as a Design Concept}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{22:1--22:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-341-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{313},
  editor =	{Aldrich, Jonathan and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2024.22},
  URN =		{urn:nbn:de:0030-drops-208715},
  doi =		{10.4230/LIPIcs.ECOOP.2024.22},
  annote =	{Keywords: Immutability, Design Enforcement, SMT, Liskov Substitution Principle, Object-oriented Programming}
}
Document
Artifact
DOI: 10.4230/DARTS.10.2.9
Constrictor: Immutability as a Design Concept (Artifact)

Authors: Elad Kinsbruner, Shachar Itzhaky, and Hila Peleg

Published in: DARTS, Volume 10, Issue 2, Special Issue of the 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
Many object-oriented applications in algorithm design rely on objects never changing during their lifetime. This is often tackled by marking object references as read-only, e.g., using the const keyword in C++. In other languages like Python or Java where such a concept does not exist, programmers rely on best practices that are entirely unenforced. While reliance on best practices is obviously too permissive, const-checking is too restrictive: it is possible for a method to mutate the internal state while still satisfying the property we expect from an "immutable" object in this setting. We would therefore like to enforce the immutability of an object’s abstract state. We check an object’s immutability through a view of its abstract state: for instances of an immutable class, the view does not change when running any of the class’s methods, even if some of the internal state does change. If all methods of a class are verified as non-mutating, we can deem the entire class view-immutable. We present an SMT-based algorithm to check view-immutability, and implement it in our linter/verifier, Constrictor. We evaluate Constrictor on 51 examples of immutability-related design violations. Our evaluation shows that Constrictor is effective at catching a variety of prototypical design violations, and does so in seconds. We also explore Constrictor with two real-world case studies.
Cite as

Elad Kinsbruner, Shachar Itzhaky, and Hila Peleg. Constrictor: Immutability as a Design Concept (Artifact). In Special Issue of the 38th European Conference on Object-Oriented Programming (ECOOP 2024). Dagstuhl Artifacts Series (DARTS), Volume 10, Issue 2, pp. 9:1-9:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Article{kinsbruner_et_al:DARTS.10.2.9,
  author =	{Kinsbruner, Elad and Itzhaky, Shachar and Peleg, Hila},
  title =	{{Constrictor: Immutability as a Design Concept (Artifact)}},
  pages =	{9:1--9:4},
  journal =	{Dagstuhl Artifacts Series},
  ISBN =	{978-3-95977-342-3},
  ISSN =	{2509-8195},
  year =	{2024},
  volume =	{10},
  number =	{2},
  editor =	{Kinsbruner, Elad and Itzhaky, Shachar and Peleg, Hila},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.10.2.9},
  URN =		{urn:nbn:de:0030-drops-209071},
  doi =		{10.4230/DARTS.10.2.9},
  annote =	{Keywords: Immutability, Design Enforcement, SMT, Liskov Substitution Principle, Object-oriented Programming}
}
Document
Artifact
DOI: 10.4230/DARTS.6.2.16
Perfect is the Enemy of Good: Best-Effort Program Synthesis (Artifact)

Authors: Hila Peleg and Nadia Polikarpova

Published in: DARTS, Volume 6, Issue 2, Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
Program synthesis promises to help software developers with everyday tasks by generating code snippets automatically from input-output examples and other high-level specifications. The conventional wisdom is that a synthesizer must always satisfy the specification exactly. We conjecture that this all-or-nothing paradigm stands in the way of adopting program synthesis as a developer tool: in practice, the user-written specification often contains errors or is simply too hard for the synthesizer to solve within a reasonable time; in these cases, the user is left with a single over-fitted result or, more often than not, no result at all. In this paper we propose a new program synthesis paradigm we call best-effort program synthesis, where the synthesizer returns a ranked list of partially-valid results, i.e., programs that satisfy some part of the specification. To support this paradigm, we develop best-effort enumeration, a new synthesis algorithm that extends a popular program enumeration technique with the ability to accumulate and return multiple partially-valid results with minimal overhead. We implement this algorithm in a tool called BESTER, and evaluate it on 79 synthesis benchmarks from the literature. Contrary to the conventional wisdom, our evaluation shows that BESTER returns useful results even when the specification is flawed or too hard: i) for all benchmarks with an error in the specification, the top three BESTER results contain the correct solution, and ii) for most hard benchmarks, the top three results contain non-trivial fragments of the correct solution. We also performed an exploratory user study, which confirms our intuition that partially-valid results are useful: the study shows that programmers use the output of the synthesizer for comprehension and often incorporate it into their solutions.
Cite as

Hila Peleg and Nadia Polikarpova. Perfect is the Enemy of Good: Best-Effort Program Synthesis (Artifact). In Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020). Dagstuhl Artifacts Series (DARTS), Volume 6, Issue 2, pp. 16:1-16:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@Article{peleg_et_al:DARTS.6.2.16,
  author =	{Peleg, Hila and Polikarpova, Nadia},
  title =	{{Perfect is the Enemy of Good: Best-Effort Program Synthesis (Artifact)}},
  pages =	{16:1--16:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2020},
  volume =	{6},
  number =	{2},
  editor =	{Peleg, Hila and Polikarpova, Nadia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.6.2.16},
  URN =		{urn:nbn:de:0030-drops-132136},
  doi =		{10.4230/DARTS.6.2.16},
  annote =	{Keywords: Program Synthesis, Programming by Example}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2020.2
Perfect Is the Enemy of Good: Best-Effort Program Synthesis

Authors: Hila Peleg and Nadia Polikarpova

Published in: LIPIcs, Volume 166, 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
Program synthesis promises to help software developers with everyday tasks by generating code snippets automatically from input-output examples and other high-level specifications. The conventional wisdom is that a synthesizer must always satisfy the specification exactly. We conjecture that this all-or-nothing paradigm stands in the way of adopting program synthesis as a developer tool: in practice, the user-written specification often contains errors or is simply too hard for the synthesizer to solve within a reasonable time; in these cases, the user is left with a single over-fitted result or, more often than not, no result at all. In this paper we propose a new program synthesis paradigm we call best-effort program synthesis, where the synthesizer returns a ranked list of partially-valid results, i.e. programs that satisfy some part of the specification. To support this paradigm, we develop best-effort enumeration, a new synthesis algorithm that extends a popular program enumeration technique with the ability to accumulate and return multiple partially-valid results with minimal overhead. We implement this algorithm in a tool called BESTER, and evaluate it on 79 synthesis benchmarks from the literature. Contrary to the conventional wisdom, our evaluation shows that BESTER returns useful results even when the specification is flawed or too hard: i) for all benchmarks with an error in the specification, the top three BESTER results contain the correct solution, and ii) for most hard benchmarks, the top three results contain non-trivial fragments of the correct solution. We also performed an exploratory user study, which confirms our intuition that partially-valid results are useful: the study shows that programmers use the output of the synthesizer for comprehension and often incorporate it into their solutions.
Cite as

Hila Peleg and Nadia Polikarpova. Perfect Is the Enemy of Good: Best-Effort Program Synthesis. In 34th European Conference on Object-Oriented Programming (ECOOP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 166, pp. 2:1-2:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{peleg_et_al:LIPIcs.ECOOP.2020.2,
  author =	{Peleg, Hila and Polikarpova, Nadia},
  title =	{{Perfect Is the Enemy of Good: Best-Effort Program Synthesis}},
  booktitle =	{34th European Conference on Object-Oriented Programming (ECOOP 2020)},
  pages =	{2:1--2:30},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-154-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{166},
  editor =	{Hirschfeld, Robert and Pape, Tobias},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2020.2},
  URN =		{urn:nbn:de:0030-drops-131593},
  doi =		{10.4230/LIPIcs.ECOOP.2020.2},
  annote =	{Keywords: Program Synthesis, Programming by Example}
}
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