λondon HUG

Next Meeting 20th September

I’m pleased to announce that the next London HUG meeting will be on Thursday 20th September at City University, starting 6:30PM. This time we have two great talks for you.

Firstly, Dr Ross Paterson of City Uni will talk about finger trees. To quote from his abstract:

“We introduce 2-3 finger trees, a functional representation of persistent sequences supporting access to the ends in amortized constant time, and concatenation and splitting in time logarithmic in the size of the smaller piece. Representations achieving these bounds have appeared previously, but 2-3 finger trees are much simpler, as are the operations on them. Further, by defining the split operation in a general form, we obtain a general purpose data structure that can serve as a sequence, priority queue, search tree, priority search queue and more.”

Afterwards Matthew Sackman and Tristan Allwood, both PhD students at Imperial College, will talk about game design in Haskell. They will hopefully be giving live demonstrations of some of the games they have developed, depending on the availability of hardware. Abstract to follow.

2 Comments, add yours.

Mailing Lists

There are two mailing lists for the London HUG:

• The announcements list is purely for announcing forthcoming meetings, or any other important news. This will be a low-volume mailing list.
• The discussion list will be for any other discussion relating to the London HUG.

Click on the links and follow the instructions to register.

Please note that both of the above lists are moderated for anti-spam purposes, so please be patient if there is a delay between sending your message and it appearing on the list.

News: Meeting no. 3 and Mailing List

Hello HUGgers! It’s time for another meeting, and this time we’re back at City University on Wednesday 25th July from 6:30PM. See the Venue page for more details of how to get there. This time we are in room A247.

This time, Lennart Augustsson has offered to give a short talk entitled “Djinn, generating code with magic?”. Sounds intriguing… however, we need more! I had offered to give a short talk on HXT, the Haskell XML Toolkit, but to my very great regret I will not be able to make it to the next meeting myself, as I will be in Japan. So we need more volunteers! Please send in your suggestions… remember, we are a small, friendly community, and a talk at any level would be very welcome.

In other news, Ganesh Sittampalam (Heffalump on IRC) has very helpfully set up two mailing lists. The first one is for announcements: this will be a low volume list, purely for announcing forthcoming meetings and so on. The second one is for discussions relating to the London HUG, for example which pub we should go to. Please try to keep general Haskell discussion off the London HUG list… they should happen in Haskell Cafe where other Haskellers outside London can benefit from them.

I will send a single personal email to everybody who previously registered for the HUG to invite you join the mailing lists. I apologize for the spam, but it’s the last one I will send.

HUG Meeting Number Two

Well, the vote results are in, and it seems you really want to meet up once a month rather than every two months. So be it! In the words of Winston Churchill, “democracy is the worst form of government except all the others that have been tried.”

Amazingly, it’s already been almost one month since the first HUG, which means we should have a meeting next week. However I don’t think it would be fair to ask anybody to prepare a talk at this short notice. I quite like the suggestion made by Ganesh that we could alternate between more informal meetings — which could be as simple as a gathering at the pub — and more structured meetings with talks and so on. This also helps those who have to travel from further afield, as they may prefer only to attend the structured talks and skip the pub (or vice versa).

Therefore, I would like to propose a trip to the pub on Wednesday 27 June from 6:30PM. Is everybody happy with the Slaughtered Lamb in Clerkenwell, or do you have any other suggestions?

For the next structured meeting let’s tentatively suggest Wednesday 25 July. Please everybody send in your suggestions for talks — either what you would like to talk about yourself, or what you would like to hear somebody else talk about — or any other ideas you might have. Thanks, and see you at the next HUG!

Thinking about Meeting Number Two

Well, the first meeting of the Haskell User Group was, I think, a great success. Simon’s talk was fascinating, as were the discussions in the pub afterwards.

However, I’d like to see if we can do better. Some of the feedback suggested that the talk went over some people’s heads, which is understandable since I think we had a number of Haskell newbies in the audience, and even a few who were merely Haskell-curious. I really would like the LHUG to be inclusive of those people, so I would hope that next time we can have a better mixture of introductory material along with some of the more advanced stuff.

Here’s my suggestion for next time. Rather than one marathon talk, lets have two short talks, perhaps just 20 to 30 minutes long. Ideally one of these would be more introductory while the other one is a little more advanced. After that I propose a debate on the subject:

“Why isn’t functional programming more widely used in industry?”

To get the ball rolling on the talks, I can offer to talk on the subject “XML Processing with HXT and Arrows”. Please have a think about whether there is anything you would like to talk about, and send in your suggestions. Hopefully you’ll come up with better ideas than mine, so I don’t have to stand up and speak.

You’ll notice on the sidebar of this site there is a poll about the frequency of HUG meetings. I know we did a show of hands during the first meeting, which indicated strong support for a monthly meeting, but I have since been persuaded that that might be overdoing it. The initial energy and excitement of a new user group can quickly dissipate, so let’s give everybody some time to contemplate the previous meeting before rushing into the next one each time. I think the talks and discussions will feel a lot fresher with a bi-monthly or quarterly meeting. Anyway, place your vote, or comment below, and we’ll go with whatever the majority decide.

Video of SPJ’s Talk is now Online

I have uploaded a video of Simon’s talk on Nested Data Parallelism to Google Video. Click on the thumbnail to watch. The slides are here in PowerPoint format.

HUG Update: Nested Data Parallelism in Haskell

The following is the abstract of the talk that will be given at the inaugural meeting of the London HUG:

Nested data parallelism in Haskell
Simon Peyton Jones, Microsoft Research

There are many approaches to exploiting multi-cores, but a particularly promising one is the “data-parallel” paradigm, because it combines massive parallelism (on both shared and distributed memory) with a simple, single-control-flow programming model.

Alas, data-parallel programming is usually restricted to “flat” data parallelism, which is good for implementers but bad for programmers. In particular, all the parallelism must appear at a single point, which excludes useful paradigms such as divide-and-conquer, and inhibits modular programming.

I’ll describe the “nested” data parallel programming model, first developed in the 90’s. It is great for programmers but much harder to implement; as a result, it’s virtually unknown in practice. We are working on fixing this, by building a high-performance implementation in Haskell. I’ll tell you how it works and give you some numbers.

After Simon’s talk, I would like to propose an open discussion, kicking off with each person sharing some background about their interest in Haskell and level of experience (the answer “no experience yet” will be absolutely acceptable — we welcome everybody from newbies to gurus). It would also be great to hear people’s ideas for what they would like to get from future HUG meetings and what format they should take.

Finally, for anybody so inclined, the nearby Slaughtered Lamb has been suggested as a suitable establishment for post-HUG refreshments. Lets hope nobody ends up like the lamb.

Announcement: first meeting of the London Haskell User Group

We are delighted to announce that the first meeting of the London Haskell User Group will take place on 23rd May 2007, at City University in central London. We would like to extend an invitation to anybody who is either already using Haskell or merely interested in learning more about it to come along.

Simon Peyton Jones will be joining us to give a talk. Simon is one of the original architects of Haskell, and continues to make significant contributions to it, including his work as the lead designer of GHC, the fastest and most advanced compiler for Haskell. He has also done very important work on new abstractions for concurrency such as Software Transaction Memory and Nested Data Parallelism.

The meeting will take place from 6:30 PM in the College Building at City University in London. See the venue page for detailed location information and directions.

If you would like to attend, please register your interest either by leaving a comment on this page, or by emailing info@londonhug.net.

Many thanks to City University and Simon Peyton Jones for their support!

Date and Time: Wednesday 23rd May, from 18:30
Location: City University, College Building, room A246
Register: info@londonhug.net

UPDATE: Please note there has been a room change, due to more people registering than expected. See the updated venue page for details.

Venue

City University very kindly supply us with space for our meetings. We are at the main campus, in the College Building on St John Street, halfway between Angel and Farringdon tube stations.

Please enter via the St John Street entrance and report to the front desk.

Here is a Google Map of the area:

City University

Here is the location of the College building in relation to the other buildings on campus: