Custom `SimpleJob` Id ignored when the `MinIterationTime` attribute is used.

[m-kovac]

Hello, just identified the issue that causes all Jobs declared as attributes to have their Id's replaced with random Job names in the summary table if the MinIterationTime attribute is used.

Steps to reproduce:
Create benchmark class and add two SimpleJob attributes as well as AllStatisticsColumn to show the Job Id. Here I just use the default example from README.

[AllStatisticsColumn]
[SimpleJob(RunStrategy.ColdStart, launchCount: 5, warmupCount: 1, iterationCount: 1, id: "Job A")]
[SimpleJob(RunStrategy.Throughput, launchCount:1, warmupCount:1, iterationCount: 5, id: "Job B")]
public class Md5VsSha256
{
    private SHA256 sha256 = SHA256.Create();
    private MD5 md5 = MD5.Create();
    private byte[] data;

    [Params(1000, 10000)]
    public int N;

    [GlobalSetup]
    public void Setup()
    {
        data = new byte[N];
        new Random(42).NextBytes(data);
    }

    [Benchmark]
    public byte[] Sha256() => sha256.ComputeHash(data);

    [Benchmark]
    public byte[] Md5() => md5.ComputeHash(data);
}

In this case the table shows correct Job Id in the table( included only 2 lines for brevity)

Method	Job	IterationCount	LaunchCount	RunStrategy	UnrollFactor	N	Mean	Error	StdDev	StdErr	Min	Q1	Median	Q3	Max	Op/s
Sha256	Job A	1	5	ColdStart	1	1000	488,140.0 ns	134,559.1 ns	34,944.57 ns	15,627.69 ns	454,800.0 ns	474,900.0 ns	475,200.0 ns	489,100.0 ns	546,700.0 ns	2,048.6
Md5	Job A	1	5	ColdStart	1	1000	512,220.0 ns	101,163.3 ns	26,271.79 ns	11,749.10 ns	483,100.0 ns	487,600.0 ns	518,800.0 ns	527,100.0 ns	544,500.0 ns	1,952.3

In case when also the MinIterationTIme attribute is added, the table shows the randomly generated Job Id

[AllStatisticsColumn]
[MinIterationTime(25)]
[SimpleJob(RunStrategy.ColdStart, launchCount: 5, warmupCount: 1, iterationCount: 1, id: "Job A")]
[SimpleJob(RunStrategy.Throughput, launchCount:1, warmupCount:1, iterationCount: 5, id: "Job B")]
public class Md5VsSha256
{
   ...
}

Method	Job	IterationCount	LaunchCount	RunStrategy	UnrollFactor	N	Mean	Error	StdDev	StdErr	Min	Q1	Median	Q3	Max	Op/s
Sha256	Job-UJDDOK	1	5	ColdStart	1	1000	498.600 us	93.2607 us	24.2195 us	10.8313 us	483.000 us	483.500 us	487.300 us	498.800 us	540.400 us	2,005.6
Md5	Job-UJDDOK	1	5	ColdStart	1	1000	552.900 us	314.1166 us	81.5751 us	36.4815 us	485.900 us	514.700 us	526.400 us	543.600 us	693.900 us	1,808.6

[MattFromRVA]

Leaving some findings here to (hopefully) help the next person.

I noticed that I can recreate the issue with other attributes like [IterationTime(100)] or [MinInvokeCount(2)] as long as it has .IsMutator set to true.

The ResolvedId is set in the Job class public string ResolvedId => HasValue(IdCharacteristic) ? Id : JobIdGenerator.GenerateRandomId(this);

So I assume somewhere along the way IdCharacteristic loses it's value.

One method of interest with my comments added. Found in the ImmutableConfigBuilder class:

private static IReadOnlyList<Job> GetRunnableJobs(IEnumerable<Job> jobs)
{
    var unique = jobs.Distinct(JobComparer.Instance).ToArray();
    var result = new List<Job>();

    foreach (var standardJob in unique.Where(job => !job.Meta.IsMutator && !job.Meta.IsDefault))
        result.Add(standardJob);

    var customDefaultJob = unique.SingleOrDefault(job => job.Meta.IsDefault);
    var defaultJob = customDefaultJob ?? Job.Default;

    if (!result.Any())
        result.Add(defaultJob);

    // If no mutatorJob then the ResolvedId names are kept in place as the code will skip this foreach.

    // Here is where the ResolvedId changes to the randomly generated value
    foreach (var mutatorJob in unique.Where(job => job.Meta.IsMutator))
    {
        for (int i = 0; i < result.Count; i++)
        {
	    // As soon as UnfreezeCopy() finishes the resolvedId changes
            var copy = result[i].UnfreezeCopy();

            copy.Apply(mutatorJob);

            result[i] = copy.Freeze();
        }
    }

    return result;
}

I also kept testing old commits and the issue was there as well. I went as far as 7/26/23 d93490d and this was still an issue.

[MattFromRVA]

@m-kovac @timcassell Ok I figured it out. PR submitted.