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Documents authored by Palsberg, Jens

Document
DOI: 10.4230/LIPIcs.ECOOP.2024.29
Generalizing Shape Analysis with Gradual Types

Authors: Zeina Migeed, James Reed, Jason Ansel, and Jens Palsberg

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

Abstract
Tensors are multi-dimensional data structures that can represent the data processed by machine learning tasks. Tensor programs tend to be short and readable, and they can leverage libraries and frameworks such as TensorFlow and PyTorch, as well as modern hardware such as GPUs and TPUs. However, tensor programs also tend to obscure shape information, which can cause shape errors that are difficult to find. Such shape errors can be avoided by a combination of shape annotations and shape analysis, but such annotations are burdensome to come up with manually. In this paper, we use gradual typing to reduce the barrier of entry. Gradual typing offers a way to incrementally introduce type annotations into programs. From there, we focus on tool support for type migration, which is a concept that closely models code-annotation tasks and allows us to do shape reasoning and utilize it for different purposes. We develop a comprehensive gradual typing theory to reason about tensor shapes. We then ask three fundamental questions about a gradually typed tensor program. (1) Does the program have a static migration? (2) Given a program and some arithmetic constraints on shapes, can we migrate the program according to the constraints? (3) Can we eliminate branches that depend on shapes? We develop novel tools to address the three problems. For the third problem, there are currently two PyTorch tools that aim to eliminate branches. They do so by eliminating them for just a single input. Our tool is the first to eliminate branches for an infinite class of inputs, using static shape information. Our tools help prevent bugs, alleviate the burden on the programmer of annotating the program, and improves the process of program transformation.
Cite as

Zeina Migeed, James Reed, Jason Ansel, and Jens Palsberg. Generalizing Shape Analysis with Gradual Types. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 29:1-29:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{migeed_et_al:LIPIcs.ECOOP.2024.29,
  author =	{Migeed, Zeina and Reed, James and Ansel, Jason and Palsberg, Jens},
  title =	{{Generalizing Shape Analysis with Gradual Types}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{29:1--29:28},
  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.2024.29},
  URN =		{urn:nbn:de:0030-drops-208786},
  doi =		{10.4230/LIPIcs.ECOOP.2024.29},
  annote =	{Keywords: Tensor Shapes, Gradual Types, Migration}
}
Document
Artifact
DOI: 10.4230/DARTS.10.2.14
Generalizing Shape Analysis with Gradual Types (Artifact)

Authors: Zeina Migeed and Jens Palsberg

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

Abstract
This is the artifact for the conference article below.
Cite as

Zeina Migeed and Jens Palsberg. Generalizing Shape Analysis with Gradual Types (Artifact). In Special Issue of the 38th European Conference on Object-Oriented Programming (ECOOP 2024). Dagstuhl Artifacts Series (DARTS), Volume 10, Issue 2, pp. 14:1-14:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Article{migeed_et_al:DARTS.10.2.14,
  author =	{Migeed, Zeina and Palsberg, Jens},
  title =	{{Generalizing Shape Analysis with Gradual Types (Artifact)}},
  pages =	{14:1--14:2},
  journal =	{Dagstuhl Artifacts Series},
  ISBN =	{978-3-95977-342-3},
  ISSN =	{2509-8195},
  year =	{2024},
  volume =	{10},
  number =	{2},
  editor =	{Migeed, Zeina and Palsberg, Jens},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.10.2.14},
  URN =		{urn:nbn:de:0030-drops-209125},
  doi =		{10.4230/DARTS.10.2.14},
  annote =	{Keywords: Gradual Types, Type Theory}
}
Document
Artifact
DOI: 10.4230/DARTS.8.2.3
Compiling Volatile Correctly in Java (Artifact)

Authors: Shuyang Liu, John Bender, and Jens Palsberg

Published in: DARTS, Volume 8, Issue 2, Special Issue of the 36th European Conference on Object-Oriented Programming (ECOOP 2022)

Abstract
The compilation scheme for Volatile accesses in the OpenJDK 9 HotSpot Java Virtual Machine has a major problem that persists despite a recent bug report and a long discussion. One of the suggested fixes is to let Java compile Volatile accesses in the same way as C/C++11. However, we show that this approach is invalid for Java. Indeed, we show a set of optimizations that is valid for C/C++11 but invalid for Java, while the compilation scheme is similar. We prove the correctness of the compilation scheme to Power and x86 and a suite of valid optimizations in Java. Our proofs are based on a language model that we validate by proving key properties such as the DRF-SC theorem and by running litmus tests via our implementation of Java in Herd7.
Cite as

Shuyang Liu, John Bender, and Jens Palsberg. Compiling Volatile Correctly in Java (Artifact). In Special Issue of the 36th European Conference on Object-Oriented Programming (ECOOP 2022). Dagstuhl Artifacts Series (DARTS), Volume 8, Issue 2, pp. 3:1-3:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@Article{liu_et_al:DARTS.8.2.3,
  author =	{Liu, Shuyang and Bender, John and Palsberg, Jens},
  title =	{{Compiling Volatile Correctly in Java (Artifact)}},
  pages =	{3:1--3:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2022},
  volume =	{8},
  number =	{2},
  editor =	{Liu, Shuyang and Bender, John and Palsberg, Jens},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.8.2.3},
  URN =		{urn:nbn:de:0030-drops-162018},
  doi =		{10.4230/DARTS.8.2.3},
  annote =	{Keywords: formal semantics, concurrency, compilation}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2022.6
Compiling Volatile Correctly in Java

Authors: Shuyang Liu, John Bender, and Jens Palsberg

Published in: LIPIcs, Volume 222, 36th European Conference on Object-Oriented Programming (ECOOP 2022)

Abstract
The compilation scheme for Volatile accesses in the OpenJDK 9 HotSpot Java Virtual Machine has a major problem that persists despite a recent bug report and a long discussion. One of the suggested fixes is to let Java compile Volatile accesses in the same way as C/C++11. However, we show that this approach is invalid for Java. Indeed, we show a set of optimizations that is valid for C/C++11 but invalid for Java, while the compilation scheme is similar. We prove the correctness of the compilation scheme to Power and x86 and a suite of valid optimizations in Java. Our proofs are based on a language model that we validate by proving key properties such as the DRF-SC theorem and by running litmus tests via our implementation of Java in Herd7.
Cite as

Shuyang Liu, John Bender, and Jens Palsberg. Compiling Volatile Correctly in Java. In 36th European Conference on Object-Oriented Programming (ECOOP 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 222, pp. 6:1-6:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{liu_et_al:LIPIcs.ECOOP.2022.6,
  author =	{Liu, Shuyang and Bender, John and Palsberg, Jens},
  title =	{{Compiling Volatile Correctly in Java}},
  booktitle =	{36th European Conference on Object-Oriented Programming (ECOOP 2022)},
  pages =	{6:1--6:26},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-225-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{222},
  editor =	{Ali, Karim and Vitek, Jan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2022.6},
  URN =		{urn:nbn:de:0030-drops-162346},
  doi =		{10.4230/LIPIcs.ECOOP.2022.6},
  annote =	{Keywords: formal semantics, concurrency, compilation}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2015.371
Type Inference for Place-Oblivious Objects

Authors: Riyaz Haque and Jens Palsberg

Published in: LIPIcs, Volume 37, 29th European Conference on Object-Oriented Programming (ECOOP 2015)

Abstract
In a distributed system, access to local data is much faster than access to remote data. As a help to programmers, some languages require every access to be local. A program in those languages can access remote data via first a shift of the place of computation and then a local access. To enforce this discipline, researchers have presented type systems that determine whether every access is local and every place shift is appropriate. However, those type systems fall short of handling a common programming pattern that we call place-oblivious objects. Such objects safely access other objects without knowledge of their place. In response, we present the first type system for place-oblivious objects along with an efficient inference algorithm and a proof that inference is P-complete. Our example language extends the Abadi-Cardelli object calculus with place shift and existential types, and our implementation has inferred types for some microbenchmarks.
Cite as

Riyaz Haque and Jens Palsberg. Type Inference for Place-Oblivious Objects. In 29th European Conference on Object-Oriented Programming (ECOOP 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 37, pp. 371-395, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{haque_et_al:LIPIcs.ECOOP.2015.371,
  author =	{Haque, Riyaz and Palsberg, Jens},
  title =	{{Type Inference for Place-Oblivious Objects}},
  booktitle =	{29th European Conference on Object-Oriented Programming (ECOOP 2015)},
  pages =	{371--395},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-86-6},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{37},
  editor =	{Boyland, John Tang},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2015.371},
  URN =		{urn:nbn:de:0030-drops-52223},
  doi =		{10.4230/LIPIcs.ECOOP.2015.371},
  annote =	{Keywords: parallelism, locality, types}
}
Document
DOI: 10.4230/DagSemRep.216
The Semantic Challenge of Object-Oriented Programming (Dagstuhl Seminar 98261)

Authors: Luca Cardelli, Achim Jung, Peter O'Hearn, and Jens Palsberg

Published in: Dagstuhl Seminar Reports. Dagstuhl Seminar Reports, Volume 1 (2021)

Abstract
Cite as

Luca Cardelli, Achim Jung, Peter O'Hearn, and Jens Palsberg. The Semantic Challenge of Object-Oriented Programming (Dagstuhl Seminar 98261). Dagstuhl Seminar Report 216, pp. 1-14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (1999)

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@TechReport{cardelli_et_al:DagSemRep.216,
  author =	{Cardelli, Luca and Jung, Achim and O'Hearn, Peter and Palsberg, Jens},
  title =	{{The Semantic Challenge of Object-Oriented Programming (Dagstuhl Seminar 98261)}},
  pages =	{1--14},
  ISSN =	{1619-0203},
  year =	{1999},
  type = 	{Dagstuhl Seminar Report},
  number =	{216},
  institution =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemRep.216},
  URN =		{urn:nbn:de:0030-drops-151022},
  doi =		{10.4230/DagSemRep.216},
}
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