[#RSRP-61062] Suggest Enumerable* optimizations

ReSharper

Suggest Enumerable* optimizations

Created: 11 Mar 08 20:33 Updated: 12 Mar 08 01:28

Component/s:

Code Analysis

Fix Version/s:

Alderman

Security Level:

Everybody (All jira users)

Original Estimate:

Unknown

Remaining Estimate:

Unknown

Time Spent:

Unknown

Build:

748

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var arr = new[] {1, 2, 3};
var x = arr.Where(i => i==2).Single();
var y = arr.Single(i => i == 2);

Both x and y assignments are functionally identical because Single() can take a "where" func parameter, but if understand everything correctly, the second call is much more efficient. R# can suggest to make this improvement automatically.

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Yuri Astrakhan - 11 Mar 08 22:24

I did some sample runs on this code, trying to determine the impact of nested yields, and got about 2085 vs 1445 ms - about 44% improvement

private static void RunJoined(int runCount)
{
    int count = 0;
    DateTime start = DateTime.Now;
    for (int i = 0; i < runCount; i++)
        count += Numbers.Count(v => v > 100);
    DateTime end = DateTime.Now;
    Console.WriteLine("duration: {0} milliseconds ({1})", (end - start).TotalMilliseconds, count);
}

private static void RunNested(int runCount)
{
    int count = 0;
    DateTime start = DateTime.Now;
    for (int i = 0; i < runCount; i++)
        count += Numbers.Where(v => v > 100).Count();
    DateTime end = DateTime.Now;
    Console.WriteLine("duration: {0} milliseconds ({1})", (end - start).TotalMilliseconds, count);
}

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Yuri Astrakhan - 11 Mar 08 22:25

Forgot for previous comment:

private static IEnumerable<int> Numbers
        {
            get
            {
                for (int i = 0; i < 10000; i++)
                    yield return i;
            }
        }