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• Trivial Projections Are (Usually) Optimized Away

  OK, computers aren't entirely dumb when it comes to LINQ. Here's an example of a place where we're a bit smarter. Consider the following query: IEnumerable<int> query = from n in number_array orderby n select n; Does this get transformed by the Read More... Posted Monday, May 12, 2008 6:57 AM by Eric Lippert | 6 Comments Filed under: Performance, C#, Immutability

• Computers are dumb

  A few short takes today, from questions I've received recently about LINQ in C# 3.0. The first question was " in the following code, does it really check every single non-negative integer, or does it use the knowledge that once you're beyond ten, you Read More... Posted Friday, May 09, 2008 8:20 AM by Eric Lippert | 11 Comments Filed under: Performance, C#

• Lambda Expressions vs. Anonymous Methods, Part Five

  Last time I demonstrated that the compiler could have to do an exponential number of bindings in order to determine whether there was a unique best overload resolution for a function call that takes a lambda. Some of you may have wondered whether we simply Read More... Posted Wednesday, March 28, 2007 7:45 AM by Eric Lippert | 6 Comments Filed under: Performance, Rarefied Heights, C#, Lambda Expressions

• Lambda Expressions vs. Anonymous Methods, Part Four

  Hey all, sorry for the long time between posts; I have been crazy busy recruiting , interviewing, fixing bugs, making performance improvements and implementing last-minute changes to the language and expression tree library. The last few posts about lambda Read More... Posted Monday, March 26, 2007 4:05 PM by Eric Lippert | 8 Comments Filed under: Performance, C#, Lambda Expressions

• 250% of what, exactly?

  I just got a question this morning about how to take two collections of items and determine how many of those items had the same name. The user had written this straightforward but extremely slow VBScript algorithm: For Each Frog In Frogs For Each Toad Read More... Posted Thursday, September 01, 2005 10:13 AM by Eric Lippert | 27 Comments Filed under: VBScript, Scripting, Performance

• Caching Dispatch Identifiers Is A Bad Idea

  About two years ago I wrote a bit about when it was legal to cache a dispatch identifier so that you didn’t have to look it up a second time . I was reminded of this today because the scripting sustaining engineering team was working on a bug that involved Read More... Posted Wednesday, August 24, 2005 3:22 PM by Eric Lippert | 3 Comments Filed under: COM Programming, Performance

• Scripting Type Library Constant Injection Performance Characteristics, Part Three

  We’ve got a system that meets all our needs for disambiguating hierarchical constants through partial or full qualification. (In the event of a collision between an enumerated type name and a value in a given library, the type name wins so that full qualification Read More... Posted Thursday, July 07, 2005 2:20 PM by Eric Lippert | 5 Comments Filed under: Scripting, Performance

• Scripting Type Library Constant Injection Performance Characteristics, Part Two

  Script developers can declare constants, variables, functions and classes at global scope by writing the appropriate lines of code. Script hosts (Internet Explorer, ASP, WSH, etc) however can only add objects to the script engine’s global scope. For practical Read More... Posted Wednesday, June 29, 2005 11:02 AM by Eric Lippert | 0 Comments Filed under: Scripting, Performance

• Scripting Type Library Constant Injection Performance Characteristics, Part One

  (Sorry about the title. I work for Microsoft; we like nouns .) Over a year ago now a reader noted in a comment to this posting that defining named constants using Const in VBScript or var in JScript is way, way faster than importing a type library. My Read More... Posted Wednesday, June 22, 2005 8:00 AM by Eric Lippert | 1 Comments Filed under: JScript, VBScript, Scripting, Performance

• High-Dimensional Spaces Are Counterintuitive, Part Five

  All of this stuff about high dimensional geometry has been known for quite a while. The novel bit that this paper is all about is how to actually build a fast index for searching a high-dimensional space where the query has a strong likelihood of being Read More... Posted Monday, June 20, 2005 10:48 AM by Eric Lippert | 2 Comments Filed under: Performance, Rarefied Heights, Mathematics, High Dimensional Spaces

• High-Dimensional Spaces Are Counterintuitive, Part Four

  It's reasonably common to have a database containing a few thousand or million points in some high-dimensional space. If you have some "query point" in that space you might like to know whether there is a match in your database. If you're looking for Read More... Posted Thursday, June 09, 2005 1:57 PM by Eric Lippert | 5 Comments Filed under: Performance, Rarefied Heights, Mathematics, High Dimensional Spaces

• High-Dimensional Spaces Are Counterintuitive, Part Three

  My next book project is ready for copyediting, the wedding invitations are sent out, my bug count is under control, I've got a layer of levelling compound poured in the basement, there's no more ivy on my roof, and I’m rigging my sailboat some time this Read More... Posted Monday, June 06, 2005 3:57 PM by Eric Lippert | 6 Comments Filed under: Performance, Rarefied Heights, Mathematics, High Dimensional Spaces

• High-Dimensional Spaces Are Counterintuitive, Part One

  A friend of mine over in Microsoft Research pointed out to me the other day that high-dimensional spaces are really counterintuitive. He'd just attended a lecture by the research guys who wrote this excellent paper and we were geeking out at a party about Read More... Posted Wednesday, May 11, 2005 1:24 PM by Eric Lippert | 10 Comments Filed under: Performance, Rarefied Heights, Mathematics, High Dimensional Spaces

• How To Obtain The Name Of The Client From The ASP Server

  Here's a question about client side vs. server side scripting that I got recently: I want to get the machine name of the client the request is being made from. With ASP I can get the IP address using this code: ipaddr = Request.ServerVariables("REMOTE_ADDR") Read More... Posted Monday, May 09, 2005 12:18 PM by Eric Lippert | 12 Comments Filed under: Scripting, Security, ASP, Performance

• Google Desktop On The Cheap Part One: Nope, That Doesn't Work

  So, how many files are we talking about here? I've got over thirty thousand source code files containing over seven million unique words. There are pretty much two kinds of words -- words that occur in one, two, a dozen files, and words that occur in Read More... Posted Wednesday, October 20, 2004 12:12 PM by Eric Lippert | 11 Comments Filed under: Scripting, Performance