Roslyn Code Gems - Performance Goals

Ever since the .NET compiler platform became open source, I’ve been poking around the Roslyn source code. It’s not often you get to look at the internals of a product with a large code base, and not surprisingly there are some gems inside. I have a collection of the gems and each gem falls into one of three categories.

1. Ideas to borrow

2. Trivia

3. Bizarre and outstanding

Today’s gem falls into category two – trivia.

Have you ever wondered what makes for a “captive” audience? According to the PerformanceGoals class, this would be an operation using from one to ten seconds of time.

static PerformanceGoals()
{
    // An interaction class defines how much time is expected to reach a time point, the response 
    // time point being the most commonly used. The interaction classes correspond to human perception,
    // so, for example, all interactions in the Fast class are perceived as fast and roughly feel like 
    // they have the same performance. By defining these interaction classes, we can describe 
    // performance using adjectives that have a precise, consistent meaning.
    //
    // Name             Target (ms)     Upper Bound (ms)        UX / Feedback
    // Instant          <=50            100                     No noticeable delay
    // Fast             50-100          200                     Minimally noticeable delay
    // Typical          100-300         500                     Slower, but still no feedback necessary
    // Responsive       300-500         1,000                   Slower yet, potentially show Wait cursor
    // Captive          >500            10,000                  Long, show Progress Dialog w/Cancel
    // Extended         >500            >10,000                 Long enough for the user to switch to something else

    // Used for throughput scenarios like parser bytes per second.
    const string Throughput_100 = "Throughput_100";

    Goals = new string[(int)FunctionId.Count];
    Goals[(int)FunctionId.CSharp_SyntaxTree_FullParse] = Throughput_100;
    Goals[(int)FunctionId.VisualBasic_SyntaxTree_FullParse] = Throughput_100;
}

Unlike the code in this post, the next entry in this series will feature a gem with potentially useful code – an optimized bit counter.