LINQ/PLINQ

LINQ & PLINQ
(Parallel) Language Integrated Query

Agenda
Introduction to LINQ basics
Overview of advanced capabilities
Demo the Basics
PLINQ intro
Demo of PLINQ

Introduction
LINQ IS...
A programming model that
Introduces queries as a “first class” concept into .NET
More leg room!
Is an abstraction level for data
Don’t you just love abstraction, it’s great!
Is another tool for embedding SQL queries into code
“This code was written by a tool” – not that kind of tool!
Allows for uniform manipulation of any data type
Consistently producing consistent consistency!

LINQ Breakdown

LINQ Breakdown - Compiler

LINQ Implementations
LINQ to Objects
Code (Reflection), Filesin FileSystem
LINQ to ADO.NET
LINQ to SQL
LINQ to DataSet
LINQ to Entities
LINQ to XML
XDocument, XElement, XAttribute, XNode, etc
In System.Xml.Linq.Document

Making Use Of Linq

Exception Handling
Calling methods where failure is possible
Make use of a ‘let’

Built In Operators
Query
Where
Projection
Select
SelectMany
Ordering
OrderBy
OrderByDescending
ThenBy
ThenByDescending
Reverse
Grouping
GroupBy
Aggregate
Count, LongCount
Sum, Average
Aggregate
Min, Max
Set
Distinct
Union, Intersect, Except
Join
Join, GroupJoin
Generation
Range, Repeat, Empty
Quantifiers
Any, All, Contains
Partitioning
Take, TakeWhile
Skip, SkipWhile
Element Operators
First, FirstOrDefault
Last, LastOrDefault
Single, SingleOrDefault
ElemenentAt, ElementAtOrDefatult
DefaultIfEmpty
Other
Concat
SequenceEqual

Extension Methods
Custom Operators
New Name
Or Override Existing Operators (potentially bad practice)
Specialise Existing – For a given type

LINQ DEMO
Basics in VS2010

Advanced LINQ
Recursive Lambda Expressions
Through the use of Fix fixed-point generator
Expression Trees
MSDN Blogs: Mads Torgersen - Recursive Lambda Expressions
Visitor Pattern using LINQ
MSDN Blogs: Jomo Fisher – Dealing with LINQs immutable expression trees

PLINQ Background
Part of managed concurrency library in the .NET Framework
Simplify concurrent processing
Makes use of the Task Parallel Library (TPL)
TPL in turn uses
Parallel.For
Parallel.ForEach
Parallel.Invoke

Operating In Parallel
Partitioning
Based on computation and data type
Range (Arrays, Lists) – Index into structure, equal split
Not the most ideal for load balancing
Striped
Chunks of input
Chunk level load balancing
Hash
Execution
On available cores
Merge Results
Initial thread picks up results (consumer thread)
ForAll, Async (pipelining), Sync (stop-and-go)
PLINQ takes care of threading events, signalling, concurrency, locking, etc.

PLINQ DEMO
Speed up of processing using multiple cores

Demo
Projections
Extension Methods
Parallel Performance
LINQ to XML
LINQ to SQL Entities

PLINQ Ideal Speedup

Thank You
Questions?
More info on my blog; links, “refined wording”: http://NickJosevski.com