Sorry to be "that guy", but what is System.Linq.Parallel? Can anyone provide a brief description/ list of links where to read more about it? Why is open sourcing it such a big deal?
Linq is a library that injects a whole bunch functional style operations on top of list-like objects. Technically speaking, its implementing a type-safe query (think SQL) language on top of them, but the difference is very minimal in practice.
What this does is allow for certain operations to automatically be run in parallel. If you wanted to add 1 to every element in an array, you could do that with with Linq:
IEnumerable<int> numbers = new List<int>() { 1, 2, 3, 4, 5 };
var newList = from num in numbers.AsParallel()
select (x => x+1);
but by adding ".asParallel()" to the chain:
var newList = from num in numbers.AsParallel()
select (x => x+1);
your code is automatically run on each element in a parallel fashion and the runtime handles marshalling it all into a queue for processing... or however it does it's magic.
I personally love Linq. To me it feels like using a Functional Relational Mapping system when combined with Linq-To-SQL, and the same semantics can be used to create a reactive programming model similar to what is intended with kefir.js and Akka ( http://msdn.microsoft.com/en-us/data/gg577609.aspx )
The idea itself isn't new, Perl 6 has something like this planned for trivial cases like for (1..10) { $_ = $_ +1; }
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I don't know the full story, but for me the significance of open sourcing this code is that it will potentially encourage forks and extensions that allow running stuff upon GPGPUs or other massively parallel architectures while still using Linq style syntax.
TL;DR:
With Linq, Anything that implements iEnumerable (lists, arrays, streams, etc) can be made to automatically support all sorts of nifty transforms. The Parallel bits let many of them run in parallel quite trivially
I hate to be nit-picky, what you're presenting is non-idiomatic C#, I would guess you're not a C# programmer. No-one really uses the SQL-esque langugage. The simple methods reads better, are quicker to type, are clearer and are more succinct. 'p', 'q' also tends to be the de facto standard operator in lambda expressions, rather than 'x', 'y' or 'i', 'j'. And why would you use IEnumerable<int> where you used it, it makes no sense?
Your code should have read:
var numbers = new List<int>() { 1, 2, 3, 4, 5 };
var newList = numbers.AsParallel().Select(p => p + 1);
Then don't :). What you've presented is very much like saying "I don't encounter many people with your style of programming and thus, no one uses that style and you're not an actual programmer in this language".
Don't forget that there are varying styles of doing things. You use 'p'? great! Others will use foo, i, j, lalal, etc. No need to get worked up over such a minor issue and detract from the actual conversation at hand.
var salesAndReturns = from sale in sales
join return in returns on new { StockId = sale.StockId, ClientStockId = sale.ClientStockId, SellPointId = sale.SellPointId }
equals new { StockId = return.StockId, ClientStockId = return.ClientStockId, SellPointId = return.SellPointId } into gpu
from subreturn in gpu.DefaultIfEmpty()
select new
{
sale.ClientStockId,
sale.StockId,
Quantity = -sale.Quantity + (subreturn ?? new SellPointStock()).Quantity
};
The are no rules restricting us from how we should use LINQ.
No one uses the sql esque language? Where do you get that idea from? I've been a c# dev for 7 years and have seen plenty. For complicate queries it's significantly more compact (and readable, in my opinion).
And using IEnumerable was probably making the point that it didn't have to be a list, it could be anything implementing that interface.
I know people with 10 years experience with the language that still use the DSL for simple cases.
There is a lot of discussion about the usage of var, and ultimape's non-usage of it in his example is a personal preference, as well as making sense in an educational post.
And lastly, I think you'll find many developers, young and old alike, use x, y and z as their lambda parameters. I do too. It comes from the mathematical function origin of the syntax. In most early examples when it was introduced, and loads of educational materials now, lambda syntax is still presented akin to a mathematical formula:
x => x+1
In that context, using x makes a lot more sense than p, and has stuck around as a habit. It's a style thing, and everybody has their own style. You don't get to claim superior experience or skill based on a 2 line snippet that doesn't match your style.
And as an aside: you're not being downvoted by "the ignorant masses". You're being downvoted for being confrontational and not contributing to a conversation about the topic, which is Parallel LINQ and not coding style.
Tch, come on, the briefest trawl through recent blog posts and you'll see the % of Scottish idioms has dropped to a small amount since people have been blogging.
Downvoters be damned, they know not what they talk about. mattmanser is clearly not an English speaker.
For simpler stuff, ya, DSL is not handy at all. But for the complex ones, shame on you if you don't DSL it. And don't come with percentage of SO questions bullshit, that's bad programmer excuse.
For longer queries, that little DSL syntax it's a bless. It's way more pleasant to read, write or think about it than the alternative.
Ah, and since you care so much about it, I've been developing in C# for freaking years that I don't bother to sum it up anymore.
SO is as much about making yourself look as smart as possible while still needing help. I would bet half of the folks submitting questions over linq use resharper to "nerdify" their code before they submit it...
Not a fan of the DSL myself, but plenty of people in this C# shop here use it.
Plus, replacing 'let' becomes ugly using methods rather quickly, for example.
I use the query syntax. And I have since .net 3 came out. I also use extension methods. In particular "let" can be much easier to accomplish in the query syntax. And I've usually used the first letter of the type I'm dealing with for my lambda parameters. I've never seen any standard that favored p or q.
I prefer the non SQL-esque way also, I find it prettier, and I rarely see it at work. As for q and p, and I always use i, and I see lots of other random letters. Does the letter used really matter?
I'd have to disagree. Sure for the simple one liner this is true. But start doing let bindings, group by, etc.. and the standard methods can get very messy.
There is nothing wrong with the DSL syntax at all.
Parallel LINQ is an extension to LINQ (Language Integrated Querying). The "parallel" hints that it is a way to process results in parallel - using multiple threads, possibly on multiple CPUs/cores.
It allows you to express patterns like fork/join in a very elegant, fluent way.
If I have a set of Orders each with a collection of OrderItems, and each OrderItem* has a Consolidate method (I know, contrived, but bear with me).
This is actually becoming my chief complaint about submissions. It appears to me as if folks now believe that it's cool to submit links which resolve as deeply and closely as possible to subject (in this case a the subdirectory inside the project's repo) with total disregard to the fact that there is insufficient (or no) information describing why we should be interested in the link or what, if anything, we should discuss.
I'm willing to bet the submitter went through a series of links beginning with some sort of announcement that something changed to get to the link they submitted. Why do folks think that we would not also benefit from that information or that it would not help to foster more interesting discussion?
Why? Probably because the "blog spam" or "only submit the original source" comments will show up and submissions get flagged. Happens enough that I would imagine the submitter probably followed all the links in response to prior submissions.
