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Tech Talk: An Introduction to Communicating Haskell Processes

March 10th, 2010 by Iavor S. Diatchki

Please note the unusual time-slot for this talk!

Details:

Title: An Introduction to Communicating Haskell Processes
Presenter: Neil Brown
Date: Monday, 15 March 2010
Time: 10:30am
Location: Galois Inc.
421 SW 6th Ave. Suite 300, Portland, OR, USA
(3rd floor of the Commonwealth building)

Abstract: Haskell is an excellent language for combining the power of functional programming with imperative constructs. This characteristic led to the development of the Communicating Haskell Processes (CHP) libraries, which support imperative synchronous message-passing in Haskell. The core ‘chp’ library provides basic message-passing, concurrency and choice, as well as integrated support for tracing. The ‘chp-plus’ library provides higher-level features such as process composition operators and behaviour combinators. This talk provides an introduction to the two libraries and the programming style they engender — as well as a brief look at the formal semantics underlying the libraries.

Bio: Neil Brown is a software researcher from the University of Kent in the UK. After graduating he worked for several years as a machine learning researcher in industry at QinetiQ, before returning to university to undertake his PhD. He started out writing a Haskell-based compiler for synchronous message-passing languages, and ended up programming some synchronous message-passing libraries for Haskell itself. As well as these CHP libraries, he also developed the Progression benchmark-graphing library for Haskell. More detail on both projects can be found on his blog.

Posted in Functional Programming, Haskell, Open Source, Tech Talks | Comments (1)

Tech Talk: Modern Benchmarking in Haskell

February 19th, 2010 by Iavor S. Diatchki

Details:

Title: Modern Benchmarking in Haskell (slides)
Presenter: Don Stewart
Date: Tuesday, 23 February 2010
Time: 10:30am
Location: Galois Inc.
421 SW 6th Ave. Suite 300, Portland, OR, USA
(3rd floor of the Commonwealth building)

Abstract: Thanks to work by Bryan O’Sullivan, there has been a renaissance in performance benchmarking tools for Haskell, built upon Criterion.

“Compared to most other benchmarking frameworks (for any programming language, not just Haskell), criterion focuses on being easy to use, informative, and robust.”

Criterion uses statistically robust mechanisms for sampling and computing sound microbenchmark results, and is more stable in the presence of noise on the system than naive timings.

Criterion has in turn spawned some extensions:

Progrssion: compare different criterion graphs
NoSlow: a new array benchmark suite based on Criterion

In this talk I will present these tools, how to use them, and how to make your performance benchmarks in Haskell, or languages Haskell can talk to, more reliable.

Bio: Don is an Australian open source hacker, and engineer at Galois, Inc, in Portland, Oregon, where he works on creating trustworthiness and assurance in critical systems with an emphasis on language design and compiler techniques. Don is co-author of the book, Real World Haskell, published by O’Reilly, and the XMonad window manager.

Galois has been holding weekly technical seminars for several years on topics from functional programming, formal methods, compiler and language design, to cryptography, and operating system construction, with talks by many figures from the programming language and formal methods communities. The talks are open and free. An RSVP is not required, but feel free to contact the organizer with questions and comments.

Posted in Haskell, Open Source, Tech Talks | Comments (1)

Tech Talk: Introduction to Aarne Ranta’s GF, the Grammatical Framework

February 11th, 2010 by Lee Pike

The talk will be presented by Iavor Diatchki on Tuesday, February 16th, at 10:30am.

(slides)
Abstract: The Grammatical Framework (created by Aarne Ranta) is a programming language for multilingual grammar applications. It may be seen in a number of different ways:

as a special-purpose language for grammars, like YACC or Happy, but not restricted to programming languages;
as a functional language, like Haskell or SML, but specialized to grammar writing;
as a logical framework, like Agda or Coq, but equipped with concrete syntax in addition to logic;
as a natural language processing framework, like LKB, or Regulus, but based on functional programming and type theory.

This talk is an introduction to GF’s basic concepts by example. We will look at how to define the meaning and syntax of a language, perform simple translations, define semantic properties, and how to use GF together with another language such as Haskell.

Bio: Iavor Diatchki is a R&D Engineer at Galois, Inc. with a Ph.D. from the Oregon Graduate Institute.

Details:

Date: February 16th, 2010, Tuesday
Time: 10:30am
Location: Galois Inc., 421 SW 6th Ave. Suite 300 (3rd floor of the Commonwealth building)

Posted in Community, Functional Programming, Haskell, Tech Talks | Comments (2)

Tech Talk: A Scalable I/O Manager for GHC

January 20th, 2010 by Iavor S. Diatchki

The talk will be presented by Johan Tibell on Friday, January 29th, at 1:30pm.

Slides are available (also on Slideshare and Scribd).

Abstract: The Glasgow Haskell Compiler supports extraordinarily cheap threads. These are implemented using a two-level model, with threads scheduled across a set of OS-level threads. Since the lightweight threads can’t afford to block when performing I/O operations, when a Haskell program starts, it runs an I/O manager thread whose job is to notify other threads when they can safely perform I/O.

The I/O manager manages its file descriptors using the select system call. While select performs well for a small number of file descriptors, it doesn’t scale to a large number of concurrent clients, making GHC less attractive for use in large-scale server development.

This talk will describe a new, more scalable I/O manager that’s currently under development and that hopefully will replace the current I/O manager in a future release of GHC.

Details:

Date: January 29th, 2010, Friday
Time: 1:30pm
Location: Galois Inc., 421 SW 6th Ave. Suite 300 (3rd floor of the Commonwealth building)

Bio: Johan Tibell is a Software Engineer at Google Inc. He received a M.S. in Software Engineering from the Chalmers University of Technology, Sweden, in 2007.

Posted in Functional Programming, Haskell, Tech Talks | Comments (0)

GHC Nominated for Programming Language Award

January 6th, 2010 by john

ACM SIGPLAN recently announced a new award:

The SIGPLAN Programming Languages Software Award is awarded to an institution or individual(s) to recognize the development a software system that has had a significant impact on programming language research, implementations, and tools. The impact may be reflected in the wide-spread adoption of the system or its underlying concepts by the wider programming language community either in research projects, in the open-source community, or commercially. The award includes a prize of $2,500.

I think that GHC (Glasgow Haskell Compiler) and the two Simons (Peyton Jones and Marlow) are prime candidates for this. So, being careful to stay within the 500 word limit, I submitted a nomination statement for GHC as follows:

For the last decade, Haskell has been at the center of the most exciting innovations within programming languages, with work on software transactional memory, generalized algebraic data types, rank-N polymorphism, monads, multi-parameter type classes, embedded domain-specific languages, property-based testing, data parallelism, thread-profiling, and so on, generating hundreds of research papers from many diverse research groups.

GHC, the Glasgow Haskell Compiler, is the vehicle that made this research possible.

It is hard to explore radical ideas on real systems, yet the GHC team created a flexible platform that allows other researchers to explore the implications of their ideas and to test whether they really work in the large. From the first beta release in 1991, GHC emphasized collaboration and open “bazaar” style development, as opposed to the “cathedral” development of most of its contemporaries. GHC was open source even before Linux made open source cool. GHC has continued in the same vein, now listing over 60 contributors to the codebase.

In those early days, efficient compilation of a higher-order, allocation-rich, lazy functional language seemed to be a pipe dream. Yet GHC has risen to be a top-flight performer in the online language performance shootout (shootout.alioth.debian.org), comparable with Java Server-6, and approaching native C in performance overall. This is a tribute to the incredible amount of profound optimization built into the compiler, with techniques like cross-module code migration, unboxed data types, and automated removal of intermediate data structures, all done through correctness-preserving transformations that exploit the algebraic simplicity of Haskell terms, even in the presence of monadic effects.

The impact GHC has had on programming language research would be sufficient to merit an award by itself, but GHC is having a corresponding influence in industry. By showing the feasibility of purely functional, statically-typed programming in the large, GHC Haskell has also had clear influence on many of the newest generation of languages, such as C#, F#, Java Generics, LINQ, Perl 6, Python, and Visual Basic 9.0. As Soma Somasegar, Microsoft Developer Division Chief, said in 2007, “One of the important themes in programming languages over recent years has been a move to embrace ideas from functional programming, [which] are helping us address some of the biggest challenges facing the industry today, from the impedance mismatch between data and objects to the challenges of the multi-core and parallel computing space.”

GHC now supports a burgeoning professional Haskell world. The O’Reilly book Real World Haskell, targeted to professional programmers and oriented to GHC, was published in 2008. It went on to win the Jolt Award for best technical book of the year. In 2009 there were 3500+ Haskell package updates, with more than 100,000 package downloads in November alone. GHC is now used across the financial sector in institutions like Credit Suisse and Standard Chartered Bank, and for high assurance software in companies like Amgen, Eaton, and Galois. Some of these companies came together in 2009 to create the Industrial Haskell Group, whose purpose is to ensure the health and longevity of GHC.

499 words. Whew! There is so much that could be said, but let’s hope this is enough. I think the case is very strong, and both Simon’s deserve honor and accolade for their work. Thank you both so much!

Posted in Functional Programming, Haskell, Open Source | Comments (4)

Tech Talk: John Launchbury presents Conal Elliott’s “Beautiful Differentiation”

December 9th, 2009 by Lee Pike

The December 15th Galois Tech Talk will be delivered by John Launchbury. He will present Conal Elliott’s 2009 ICFP paper entitled Beautiful Differentiation for those of us who were not able to attend this wonderful talk in-person.

Date: Tuesday, 10:30am, 15 Dec 2009
Time: 10:30am – 11:30am
Location: Galois, Inc.
421 SW 6th Ave. Suite 300
(3rd floor of the Commonwealth Building)
Portland, OR 97204

Abstract: Automatic differentiation (AD) is a precise, efficient, and convenient method for computing derivatives of functions. Its forward-mode implementation can be quite simple even when extended to compute all of the higher-order derivatives as well. The higher-dimensional case has also been tackled, though with extra complexity. This paper develops an implementation of higher-dimensional, higher-order, forward-mode AD in the extremely general and elegant setting of calculus on manifolds and derives that implementation from a simple and precise specification.

In order to motivate and discover the implementation, the paper poses the question, “What does AD mean, independently of implementation?‚” An answer arises in the form of naturality of sampling a function and its derivative. Automatic differentiation flows out of this naturality condition, together with the chain rule. Graduating from first-order to higher-order AD corresponds to sampling all derivatives instead of just one. Next, the setting is expanded to arbitrary vector spaces, in which derivative values are linear maps. The specification of AD adapts to this elegant and very general setting, which even simplifies the development.

Bio: John Launchbury is the founder and Chief Scientist of Galois, Inc.

Posted in Functional Programming, Haskell, Misc, Tech Talks | Comments (2)

Domain Specific Languages for Domain Specific Problems

October 13th, 2009 by donstewart

We have a new position paper on the use of EDSLs and Haskell for tackling the “programmability gap” of emerging high performance computing architectures — such as GPGPUs. It will be presented tomorrow at LACSS in Santa Fe. (Download) :: PDF

Slides for the talk, including a 10 minute guide to EDSLs in Haskell, and a 10 minute guide to multicore programming in Haskell, can be found here :: PDF.

Domain Specific Languages for Domain Specific Problems
Don Stewart, Galois.
Workshop on Non-Traditional Programming Models for High-Performance Computing, LACSS 2009.

As the complexity of large-scale computing architecture increases, the effort needed to program these machines efficiently has grown dramatically. The challenge is how to bridge this “programmability gap”, making the hardware more accessible to domain experts. We argue for an approach based on
executable embedded domain specific languages (EDSLs)—small languages with focused expressive power hosted directly in existing high-level programming languages such as Haskell. We provide examples of EDSLs in use in industry today, and describe the advantages EDSLs have over general purpose languages in productivity, performance, correctness and cost.

Thanks to Magnus Carlsson, Dylan McNamee, Wouter Swiestra, Derek Elkins and Alex Mason for feedback on drafts.

Posted in Functional Programming, Haskell | Comments (2)

Tech Talk: Verifying Stream Fusion with Isabelle/HOLCF

June 23rd, 2009 by Levent Erkok

The June 30th Galois Tech Talk will be delivered by Brian Huffman, titled “Verifying Stream Fusion with Isabelle/HOLCF”

Date: Tuesday, June 30th, 2009
Time: 10:30am – 11:30am
Location: Galois, Inc.
421 SW 6th Ave. Suite 300
(3rd floor of the Commonwealth Building)
Portland, OR 97204

Slides from the talk.

Abstract: Stream fusion is a system for removing intermediate data structures from Haskell programs that manipulate lists. Formal verification of such libraries requires very precise modeling in a theorem prover, to avoid strictness-related bugs.

In this talk I will present a formalization of the stream fusion library in Isabelle/HOLCF, a theorem proving environment designed especially for reasoning about functional programs. I will show how to prove the correctness of various stream functions using “fixed-point induction”, a powerful reasoning principle for general recursive functions.

Bio: Brian Huffman is a PhD student in Computer Science at Portland State University, working with advisor John Matthews. He studies formal reasoning with the Isabelle theorem prover, specializing in formalized mathematics and semantics of functional languages. He is currently the maintainer of Isabelle/HOLCF, a logic for domain theory.

Posted in Community, Formal Methods, Functional Programming, Haskell, Tech Talks, Technology | Comments (0)

Tech Talk: Orc in Haskell

June 9th, 2009 by Levent Erkok

The June 16th Galois Tech Talk will be delivered by Trevor Elliott, titled “Orc in Haskell.”

Date: Tuesday, June 16th, 2009
Time: 10:30am – 11:30am
Location: Galois, Inc.
421 SW 6th Ave. Suite 300
(3rd floor of the Commonwealth Building)
Portland, OR 97204

Abstract: Concurrency is difficult to realize successfully. The Orc language tackles this problem by introducing explicit concurrency as part of its core. It presents a clean, and somewhat monadic, style of programming that should look familiar to Haskell users. I will give a quick introduction to the Orc language, using several examples to motivate its use. Following this introduction, a monadic Haskell embedding of the major features will be presented, bringing a type system to Orc.

Bio: Trevor Elliott is a member of the technical staff at Galois, Inc. His interests center around functional programming, and the effective use of type systems.

Slides are available for download.

Posted in Community, Functional Programming, Haskell, Misc, Tech Talks | Comments (5)

Engineering Large Projects in Haskell: A Decade of FP at Galois

April 27th, 2009 by donstewart

Galois has been building systems in Haskell for the past decade. This talk describes some of what we’ve learned about in-the-large, commercial Haskell programming in that time. (Download slides :: .pdf).

When and where we use Haskell
Correctness, productivity, scalabilty, maintainability
What language features we like: types, purity, types, abstractions, types, concurrency, types!
The Haskell toolchain: FFI, HPC, Cabal, compiler, libraries, build systems, etc.
Being a commercial entity in a largely open source community

This talk was presented Monday 20th April at λondon HUG.

Posted in Community, Functional Programming, Haskell, Open Source | Comments (6)