Category Archives: visual studio

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SQLite C# port raises hopes for a Silverlight local database manager

Yesterday programmer Noah Hart announced a port of SQLite to C#:

I am pleased to announce that the C# port is done to the point where others can look at it.

Unfortunately the code was taken offline almost immediately afterwards, thanks to the intervention of the author of SQLite, D Richard Hipp:

Noah, you are welcomed, even encouraged, to take the source code to SQLite and translate it in any way you want and do whatever you want with it. But you need to make it abundantly clear to everyone on your site and in the comments of your source code that your code is not the original SQLite … SQLite is a registered trade mark. If I don’t defend the trademark, then I could lose it. So, I really do need to insist that you not use the name "SQLite" for your product.

The reason given is that Dr Hipp does not want to receive support requests for the port, though the intervention is a little surprising since there are other 3rd party adaptions out there that do use the SQLite name, though these generally modify or wrap the original code rather than porting it completely.

Still, Hart has taken it in his stride and it looks as if the code may be back soon under the name sqlsharp – a Google code project with that name has been created. I hope this is the name since I suggested it, though it is rather an obvious one and I might not have been the first.

Why the interest? First, it’s always interesting to compare languages. Currently, Hart says his executable compiles to 528kb vs 506kb for the native version, and performs 3-5 times more slowly (results in rows per second):

Test SQLite3 C# SQLite3
Inserts 300K 1300K
Selects 1500K 8450K
Updates 60K 300K
Deletes 250K 700K

Although that may seem disappointing, SQLite is remarkably fast so even 5 times slower is still acceptable in many contexts; and there are no doubt many possibilities for optimisation.

What’s the point? Hart says it was a C# learning exercise, which is fair enough. Others are hopeful for a local database manager for Microsoft Silverlight, writing to isolated storage. Competitor Adobe AIR includes SQLite in the runtime, as does Google Gears.

Silverlight may a stretch for Hart’s port. Silverlight does not allow platform invoke or code marked as unsafe; and while there are apparently only a few p/invoke calls I’m guessing there may be many unsafe sections since the original SQLite makes heavy use of pointers.*

Although Silverlight is an implementation of the .NET Framework, it does not include the System.Data namespace. It does include System.Linq.

There are a few other efforts at creating a local database manager for Silverlight, including McObject’s Perst, db4o (work in progress), and Silverlight Database which works by persisting XML.

*Update: the project has now been published as csharp-sqlite, which is an excellent name; it looks as if Hipp relented to some extent. Now that I’ve seen the code I find I’m wrong about unsafe sections. In fact, I added C#-Sqlite to a Silverlight project and it failed to compile with a mere 53 errors, many of them related to file locking – possibly less necessary in isolated storage? A Silverlight port looks feasible.

Is Mono safe to use?

Microsoft has promised not to sue those who develop implementations of its C# language and Common Language Infrastructure – the heart of .NET.

You might assume that to be good news for Mono, the open source implementation of .NET sponsored by Novell; and I suppose it is, though not in any major way.

The key point here is that Microsoft’s .NET platform goes well beyond what is covered by the promise. ASP.NET, Windows Forms, ADO.NET, Windows Presentation Foundation, Silverlight: all this falls outside. The promise covers only what is standardised by ECMA.

Mono leader Miguel de Icaza is clear about the differences in his post, and says Mono will be split into safe and – presumably – unsafe parts:

In the next few months we will be working towards splitting the jumbo Mono source code that includes ECMA + A lot more into two separate source code distributions. One will be ECMA, the other will contain our implementation of ASP.NET, ADO.NET, Winforms and others.

A good thing? Well, it could help promote the core of Mono in the open source community, which is wary. Open source champion Richard Stallman recently stirred up debate on the subject by proclaiming C# dangerous, in what has become a somewhat perplexing post:

It is dangerous to depend on C#, so we need to discourage its use. … The problem is not unique to Mono; any free implementation of C# would raise the same issue. The danger is that Microsoft is probably planning to force all free C# implementations underground some day using software patents.

he says (and is unlikely to be comforted by Microsoft’s recent moves), though he adds:

This is not to say that implementing C# is a bad thing. Free C# implementations permit users to run their C# programs on free platforms, which is good. (The GNU Project has an implementation of C# also, called Portable.NET.) Ideally we want to provide free implementations for all languages that programmers have used.

Confusing. Still, it’s a valid and important question. Is Mono safe to use?

I have been asking myself this for many years; and have asked Microsoft about it on a number of occasions with no clear answer. However, to me the breakthrough came when Moonlight was announced, an implementation of Silverlight for Linux for which Microsoft has partnered with Mono. The dual significance is first, that Microsoft is working with Mono; and second, that it shows how Microsoft has realised that overall Mono is more a benefit than a threat to its platform.

Action against Mono now seems less likely than ever. That opinion is not based on legal knowledge, but on the business & PR case.

Nevertheless, there could be limits. Stallman’s recent statement was provoked by discussions over whether Mono should be part of the default Debian install. It is not; but it is rising higher on the list of packages that are likely to be installed sooner rather than later by users, because Mono applications are growing in number.

On the server, Mono’s implementation of ASP.NET is now rather good. I’m using it on ITWriting.com for a Silverlight demo. I’ve been impressed by its compatibility with Visual Studio, though I’ve also found it increasing resource usage more than I would like. I’m using what is now an old version though, so I expect this to improve.

The cost savings in using Linux+Mono rather than Windows+ASP.NET are significant, which implies that the potential cost to Microsoft is significant too. It’s only a potential cost, because frankly the official platform is still less risky for a commercial deployment, from a technical rather than legal perspective. Mono is currently more likely to attract free or hobbyist users; but that could change. If Microsoft saw server license sales bleeding away because of Mono, my guess is that there would be rumbles.

What then of de Icaza’s move to separate Mono into safe and unsafe parts? I see the sense of it, but wonder if it could be counter-productive. While Mono is, errm, monolithic, Microsoft cannot take action against the unsafe parts without also blocking the safe parts. After the split, it will be easier for Microsoft to agitate about the pieces of Mono which might (or might not; I’m no lawyer) infringe its rights.

It still strikes me as unlikely that Microsoft would risk full-on legal action against its partner and against what is now a significant part of its platform story. However, I doubt we will get any further comfort from the company, beyond what it has already given.

*updated to acknowledge that Silverlight and WPF are covered by the open spec promise – see links in the comments.

Eclipse survey shows Windows decline

In May 2009 the open source Eclipse project surveyed its users. Visitors to the Eclipse site were asked to complete a survey, and 1365 did so. That’s out of around 1 million visitors, which shows how much we all hate surveys. Anyway, this report [pdf] was the result. A similar survey [pdf] was carried out in 2007, potentially making a valuable comparison, though the earlier survey has different questions making direct comparisons difficult in most cases, which is a shame. I especially missed the detail on which Eclipse projects are used most which is well covered in the 2007 report.

Here is what I found interesting. First, there’s a shift towards Linux and Apple Mac in the desktops developers use for Eclipse. In 2007 it was 73.8% Windows, 20% Linux and 3.5% Mac. In 2009 it is 64% Windows, 26.9% Linux and 6.9% Mac.

This is echoed in deployment platforms too (client and server). In 2007 it was 46.5% Windows, 36.6% Linux, 1% Mac; today it is 40.5% Windows, 42.7% Linux, 3% Mac.

Those surveyed were asked what other IDEs they used. I noticed that Microsoft Visual Studio and NetBeans feature fairly strongly; I also noticed that Embarcadero’s JBuilder is hardly a blip on the chart – intriguing, given how popular this used to be in the pre-Eclipse era.

The most popular code management tool is Subversion (57.5%) followed by CVS (20%). For build tools, Ant (33.4%) and Maven (18%).

Here’s an intriguing one: I often hear that Java is only successful on the server. That presumption is not supported by this survey. 23.4% said that desktop client apps are the primary type of software they are developing, compared to 30.2% server, and 24.7% web or RIA apps.

The preferred app server is Apache Tomcat (34.8%) followed by JBoss (12.7%) and Websphere (6.9%).

The most popular database manager is MySQL (27.7%) followed by Oracle (27.3%). That’s 55% for Sun+Oracle, of course, though bear in mind that many of the MySQL users are likely attracted by its free licence.

Before drawing too many conclusions, bear in mind that it is a small sample self-selected by people willing to take the survey; apparently it was also featured by a German technology site which resulted in a larger response from German visitors.

Although it suggests a declining use of Windows – which is especially plausible given the trend towards web applications – it does not prove it beyond the Eclipse community.

And next time – how about using the same questions, which would make it possible to identify trends?

I’ve also written about Eclipse here: The Eclipse Conundrum: can it grow without hurting its contributors?

Does Visual Basic have a future?

I was interested in this podcast with a member of the Visual Basic team at Microsoft, Lisa Feigenbaum, as I ask myself the same question.

Unfortunately the questioning from Joe Stagner (who also works for Microsoft) is tame. Nevertheless, there are a few points of interest.

“The things that come out of Microsoft, it is C# biased” admits Feigenbaum, which she says is because so many at Microsoft have a C or Java background.

That is part of the reason (though more C than Java) but I doubt it is that simple. If you go back to the beginnings of .NET, Microsoft designed C# and what was then the new framework and runtime together. VB on the other hand was hauled into the new world and still bears the scars.

Let’s answer the question first. Microsoft cannot afford to abandon VB, which remains popular, especially (though certainly not exclusively) at the less professional end of the market. VB isn’t going away.

Further, there’s really very little difference in the capabilities of the two languages, so there is little incentive for anyone to switch. Microsoft has attempted to differentiate them, but these attempts generally fail. “Any time we do something cool in one language, the other folks want it” says Stagner in the podcast.

As I see it, that’s part of the problem. It begs the question: what is the point of VB, other than to keep existing VB developers happy? In what circumstances would you advise a new programmer to learn VB rather than C#?

I dip in and out of both VB and C#, and of the two I prefer C#. I find VB’s slightly increased verbosity annoying, and I dislike the statement continuation character which is unnecessary in C#, because statements end with semicolons. I prefer case-sensitive languages, which give more flexibility when naming variables. If you want to do XNA games programming, currently only C# is supported. 

VB’s dynamic features are useful in some scenarios, particularly Office automation, though this advantage is removed in C# 4.0 which has dynamic variables.

The original attraction of BASIC, its English-like syntax, is nearly lost in today’s VB.

Well, choice is good; and the existence of VB alongside C# proved the cross-language credentials of the “common language” runtime from the get-go.

Nevertheless, I’m expecting VB usage to decline gradually. An external factor is the rise of the JavaScript family, which is more like C# than VB.

Incidentally, Feigenbaum threw in a comment about Visual Studio that I found interesting. After talking about the managed code editor in Visual Studio 2010, she remarks “In the release after 1010 we’re rewriting the compilers in managed code.”

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Survey ranks developer tools, and reveals what developers care about most

Evans Data has published its 2009 Software Development Platforms survey, to which around 1200 developers contributed, scoring their chosen development tools in eighteen different categories.

The tools covered are Eclipse, Embarcadero’s Delphi, IBM’s Rational Suite, IntelliJ, Microsoft’s Visual Studio, NetBeans, Oracle JDeveloper and Sun Studio.

I was sorry not to see more products covered. Flex Builder Flash Builder, Zend Studio, Aptana and JBuilder would all have been interesting, for example. Each developer only scored the product they actually use (a good thing), so the sample is not as big as it first appears.

I’m also mistrustful of the survey results, particularly when you look at it in detail. For example, one of the categories is “Support for frameworks”.  Visual Studio came top, while Eclipse was last. But hang on: in Visual Studio (for example) are we talking MFC, or .NET Framework? The development experience for each is totally different. And were developers primarily judging on the framework tools, or the framework itself? It is hard to attach much meaning to the scores in this category.

Another flaw: the versions of the products is not specified. That means a weakness may have been fixed in a later version, but the survey does not tell you.

A third flaw: some tools are weak in several categories, dragging down their overall score, but that does not matter to developers who do not use them for that purpose. It is hard to compare like with like.

Still, while I’m wary of the survey overall, I though it brought out some interesting points. One is that developers were asked what features matter most to them. So:

The three things developers care about most (highest priority first):

1. Basic tools (editor/compiler/debugger)

2. Documentation

3. Tool integration

The things developers care about least (lowest priority first):

1. Support for remote development

2. Support for parallel programming (sorry Intel!)

3. App Modeling tools

What about the winners and losers in the survey? I almost forgot. IBM’s Rational Suite came top, followed by Microsoft’s Visual Studio. Eclipse came last, though it still got a decent score, well below its rival NetBeans.

The low ranking for Eclipse (which is nevertheless wildly popular) deserves some comment, particularly as the top tool, IBM Rational Suite, is built on Eclipse. I spoke to Eclipse executive director Mike Milinkovich while researching this Register piece recently. One of the points we discussed was the tension (if there is one, which he disputes) between tools vendors sharing resources to build the best possible platform, and holding resources back to retain commercial differentiation. I’ll write this up in more detail shortly; but it shows why certain areas in Eclipse may not receive the attention they deserve – localization was a specific example.

Another problem with Eclipse is that it is all a bit messy, confusing and hard to manage, particularly in a team where you want every member to have an identical setup. It is still worth it though, for the riches it provides for free.

Microsoft having another go at Windows help: Help 3

Online help is a part of Windows full of dead-ends and back-alleys. I’m not going to attempt the story in detail here; but it goes back many years. By online help I mean local help of course; in ancient times the word “online” meant something on your computer as opposed to being in a printed book.

The first help engine I remember was in Windows 3.x, called WinHelp, and used .hlp files. It was well-liked, but authoring the files was an arcane process involving Word, RTF, a help compiler, and a certain amount of black magic.

In 1997 Microsoft replaced .hlp with .chm (compiled HTML); its initial efforts were less good than the old .hlp, but this evolved into a decent help engine despite one or two quirks.

After that it gets messy. In 2001 Microsoft announced Help 2, still HTML based but with all sorts of improvements. It was used by MSDN and in Visual Studio; its viewer is the Microsoft Document Explorer. However, and despite the help authoring tool vendors getting all geared up for Help 2, Microsoft announced in 2003 that it would not be made into a general Windows help engine, but only used for Visual Studio. Since then Help 2 has had a curious status; it is possible to author for Help 2, and those building Visual Studio extensions have needed to do so, but it has never replaced compiled HTML.

There was a similar story with Vista Help. Microsoft built a new help engine for Vista but drew back from making this available to 3rd party applications. In fact, there is a rather wonderful tool called Guided Help which lets you include application automation within Help, complete with “show me” and “do it” functionality. You can get the Guided Help SDK if you know where to look, and it works, but the project was mostly abandoned. You are still meant to use HTML Help 1.4 for your own applications.

Now Microsoft is talking about Help 3. Microsoft’s Terry Clancy mentions it in an informative post about Visual Studio 2010:

Visual Studio 10 will come with a completely re-engineered Help system that introduces a new flexible, standards based Help framework which will ultimately be used in other products beyond Visual Studio. Help3 is a help system replacement for Microsoft Help 2.x . This new help system will be easier to produce content for, and will interfere less with Visual Studio itself. The standards based approach delivers not only a much better local experience but also a seamless transition to an online web browser and with infrastructure and tooling much more consistent other Visual Studio and internet technologies.

Will Help 3 ever replace the seemingly immortal HTML Help 1.x? Place your bets.

In practice, desktop help is less important than it used to be. Online help now means the Internet; or users just use Google.

New Visual Studio 2010 beta has WPF editor, Silverlight designer

I’ve just downloaded and installed the Visual Studio 2010 beta 1 release. I’ve not explored much yet – and it is rather slow in a virtual machine – but it does now seem to have the new editor and other pieces built with Windows Presentation Foundation.

A landmark for both WPF and Visual Studio.

I also noticed that the Silverlight visual designer now works as you would expect, though I had to download the developer runtime and SDK separately:

I’d welcome comments from anyone using the beta.

Silverlight: developer win, designer fail?

I posed this question in a post over on itjoblog. There are several reasons why Silverlight struggles to get designer attention, including:

1. Designers are pragmatic and target the runtime that is already deployed most broadly, ie. Flash.

2. Flash is already good enough so why bother?

3. The tools: Adobe’s designer tools are a de facto standard, target Flash, and run on the Mac.

Developer is another matter. The cross-platform .NET runtime is Silverlight’s big advantage; and this time the tools tip the balance towards Microsoft (Visual Studio) – not for everyone, but for the substantial Microsoft platform community. That’s going to be further reinforced by Visual Studio 2010 which gets full visual designer support, plus of course Silverlight 3.0.

Microsoft does have a problem with Silverlight out of the browser. Developers need a way to have these run with more local permissions, subject to user consent, otherwise they will turn to Adobe AIR. Actually the whole Silverlight on the desktop story is confused, since you can also do Silverlight Mesh-Enabled Web Applications, or stick Silverlight content in a desktop gadget or other embedded browser. No, not the one in AIR (nice idea though): Adobe only includes Flash support and the PDF plug-in.

The tension behind this is that ultimately developers and designers need to work on the same applications, so this remains a fascinating contest.

A Silverlight database application with image upload

I’ve been amusing myself creating a simple online database application using Silverlight. I had this mostly working a while back, but needed to finish off some pieces in order to get it fully functional.

This is created using Silverlight 2.0 and demonstrates the following:

  • A bound DataGrid (as you can see, work is still needed to get the dates formatted sensibly).
  • Integration with ASP.NET authentication. You have to log in to see the data, and you have to log in with admin rights to be able to update it.
  • Create,Retrieve,Update,Delete using ASP.NET web services.
  • Image upload using Silverlight and an ASP.NET handler.
  • Filter a DataGrid (idea taken from here).
  • Written in Visual Studio 2008, and hosted on this site, which runs Debian Linux, hence Mono and MySQL. Would you have known if I had not told you?

You can try it here. I’ll post the code eventually, but it will be a couple of months as it links in with another article.

MVP Ken Cox notes in a comment to Jesse Liberty’s blog:

Hundreds of us are scouring the Internet for a realistic (but manageable and not over-engineered) sample of manipulating data (CRUD operations) in a Silverlight 2 application. There are promising pieces of the puzzle scattered all over the place. Unfortunately, after investing time in a sample, we discover it lacks a key element – like actually saving changed data back to the database.

I can safely say that mine is not over-engineered, and that yes, it does write data.

Parallel Programming: five reasons for caution. Reflections from Intel’s Parallel Studio briefing.

I’m just back from an Intel software conference in Salzburg where the main topic was Parallel Studio, a new suite which adds Intel’s C/C++ compiler, debugging and profiling tools into Visual Studio. To some extent these are updates to existing tools like Thread Checker and VTune, though there are new features such as memory checking in Parallel Inspector (the equivalent to Thread Checker) and a new user interface for Parallel Amplifier (the equivalent to VTune). The third tool in the suite, Parallel Composer, is comprised of the compiler and libraries including Threading Building Blocks and Intel Integrated Performance Primitives.

It is a little confusing. Mostly Parallel Studio replaces the earlier products for Windows developers using Visual Studio; though we were told that there are some advanced features in products like VTune that meant you might want to stick with them, or use both.

Intel’s fundamental point is that there is no point in having multi-core PCs if the applications we run are unable to take advantage of them. Put another way, you can get remarkable performance gains by converting appropriate routines to use multiple threads, ideally as many threads as there are cores.

James Reinders, Intel’s Chief Evangelist for software products, introduced the products and explained their rationale. He is always worth listening to, and did a good job of summarising the free lunch is over argument, and explaining Intel’s solution.

That said, there are a few caveats. Here are five reasons why adding parallelism to your code might not be a good idea:

1. Is it a problem worth solving? Users only care about performance improvements that they notice. If you have a financial analysis application that takes a while to number-crunch its data, then going parallel is a big win. If your application is a classic database forms client, it is probably a waste of time from a performance perspective. You care much more about how well your database server is exploiting multiple threads on the server, because that is likely to be the bottleneck.

There is a another reason to do background processing, and that is in order to keep the user interface responsive. This matters a lot to users. Intel said little about this aspect; Reinders told me it is categorised as convenience parallelism. Nevertheless, it is something you probably should be doing, but requires a different approach than parallelising for performance.

2. Will it actually speed up your app? There is an overhead in multi-threading, as you now have to manage the threads as well as performing your calculations. The worst case, according to Reinders, is a dual-core machine, where you have all the overhead but only one additional core. If the day comes when we routinely have, say, 64 cores on our desktop or laptop, then the benefit becomes overwhelming.

3. Is it actually desirable on a multi-tasking operating system? Consider this: an ideally parallelised application, from a performance perspective, is one that uses 100% CPU across all cores until it completes its task. That’s great if it is the only application you are running, but what if you started four of these guys (same or different applications) simultaneously on a quad-core system? Now each application is contending with others, there’s no longer a performance benefit, and most likely the whole system is going to slow down. There is no perfect solution here: sometimes you want an application to go all-out and grab whatever CPU it needs to get the job done as quickly as possible, while sometimes you would prefer it to run with lower priority because there are other things you care about more, such as a responsive operating system, other applications you want to use, or energy efficiency.

This is where something like Microsoft’s concurrency runtime (which Intel will support) could provide a solution. We want concurrent applications to talk to the operating system and to one another, to optimize overall use of resources. This is more promising than simply maxing out on concurrency in every individual application.

4. Will your code still run correctly? Edward Lee argues in a well-known paper, The Problem with Threads, that multi-threading is too dangerous for widespread use:

Many technologists are pushing for increased use of multithreading in software in order to take advantage of the predicted increases in parallelism in computer architectures. In this paper, I argue that this is not a good idea. Although threads seem to be a small step from sequential computation, in fact, they represent a huge step. They discard the most essential and appealing properties of sequential computation: understandability, predictability, and determinism. Threads, as a model of computation, are wildly nondeterministic, and the job of the programmer becomes one of pruning that nondeterminism. Although many research techniques improve the model by offering more effective pruning, I argue that this is approaching the problem backwards. Rather than pruning nondeterminism, we should build from essentially deterministic, composable components. Nondeterminism should be explicitly and judiciously introduced where needed, rather than removed where not needed.

I put this point to Reinders at the conference. He gave me a rather long answer, saying that it is partly a matter of using the right libraries and tools (Parallel Studio, naturally), and partly a matter of waiting for something better:

Law articulates the dangers of threading. Did we magically fix it or do we really know what we’re doing in inflicting this on the masses? It really come down to determinism. If programmers make their program non-deterministic, getting out of that mess is something most programmers can’t do, and if they can it’s horrendously expensive.

He’s right, if we stayed with Windows threads and Pthreads and programming at that level, we’re headed for disaster. What you need to see is tools and programming templates that avoid that. The evil thing is what we call shared mutable state. When you have things happening in parallel, the safest thing you can do is that they’re totally independent. This is one of the reasons that parallelism on servers works so well, in that you do lots and lots of transactions and they don’t bump into each other, or they only interface through the database.

Once we start opening up shared mutable state, encouraging threading, we set ourselves up for disaster. Parallel Inspector can help you figure out what disasters you create and get rid of them, but ultimately the answer is that you need to encourage people to use programming like OpenMP or Threading Building Blocks. Those generally guide you away from those mistakes. You can still make them.

One of the open questions is can you come up with programming techniques that completely avoid the problem? We do have one that that we’ve just started talking about called Ct … but I think we’re at the point now where OpenMP and Threading Building Blocks have proven that you can write code with that and get good results.

Reinders went on to distinguish between three types of concurrent programming, referring to some diagrams by Microsoft’s David Callaghan. The first is explicit, unsafe parallelism, where the developer has to do it right. The second is explicit, safe parallelism. The best approach according to Reinders would be to use functional languages, but he thinks it unlikely that they will catch on in the mainstream. The third type is implicit parallelism that’s safe, where the developer does not even have to think about it. An example is the math kernel library in IPP (Intel Integrated Performance Primitives) where you just call an API that returns the right answers, and happens to use concurrency for its work.

Intel also has a project called Ct (C/C++ for Throughput) which is a dynamic runtime for data parallelism, which Reinders considers also falls into the implicit parallelism category.

It was a carefully nuanced answer, but proceed with caution.

5. Will your application need a complete rewrite? This is a big maybe. Intel’s claim is that many applications can be updated for parallelism with substantial benefits. A guy from Nero did a presentation though, and said that an attempt to parallelise one of their applications, a media transcoder, had failed because the architecture was not right, and it had to be completely redone. So I guess it depends.

This brings to mind another thing which everyone agrees is a hard challenge: how to design an application for effective parallelism. Intel has a tool in preparation called Parallel Advisor, to be part of Parallel Studio at a future date, which is meant to identify candidates for parallelism, but that will not be a complete answer.

Go parallel, or not?

None of the above refutes Intel’s essential point: that effective concurrent programming is essential to the future of computing. This is an evolutionary process though, and at this point there is every reason to be cautious rather than madly parallelising every piece of code you touch.

Additional Links

Microsoft has a handy Parallel Computing home page.

David Callaghan: Design considerations for Parallel Programming