Month: January 2023

Improved Application Performance with .NET 7

Pranav Negandhi

Speed has been a big selling point for .NET 7. Stephen Toub has written an extremely lengthy and detailed article back in August 2022 about all the performance improvements that went into it. And it’s ridiculously easy to take advantage of the speed boost in your own applications. In most cases, it only requires recompiling your project to target the new runtime. Developers who don’t make the switch are leaving a lot of performance gains on the table. I took some effort to measure the speed improvements by running some benchmarks on my own projects.

Shades is a .NET port of the Python module of the same name, for creating generative art. The module was originally authored by Ben Rutter. The library operates by decomposing any drawing operation, no matter how complex, into a series of single-pixel modifications, executed one at a time, across the entire bitmap. To draw a line, the library first calculates every pixel that makes the line, then iterates through that list to compute its colour value, and making a discrete set pixel call for it. Drawing primitive shapes using solid colours is delegated to the much faster SkiaSharp library. But all the more advanced effects which have no equivalent operation in SkiaSharp have to be done with custom routines.

So of course it is slow. And anything that makes it go faster is a welcome improvement.

For this exercise, I chose the PixelsInsideEdge method, which operates on the coordinates that make up the outer edge of a shape, and identifies the pixels that fall within that boundary. It uses a simplified implementation of a ray-casting algorithm to determine whether a point is within the shape boundary or falls outside of it.

public ICollection<SKPoint> PixelsInsideEdge(ICollection<SKPoint> edgePixels)
{
    /// Contains a list of distinct values along the X axis, extracted from edgePixels.
    /// Each unique value along the X axis corresponds to a list of unique values along
    /// the Y axis that intersect with the X coordinate.
    var xs = new SortedDictionary<int, SortedSet<int>>();
    int minX = int.MaxValue, minY = int.MaxValue, maxX = int.MinValue, maxY = int.MinValue;
    foreach (var e in edgePixels)
    {
        var ex = Convert.ToInt32(e.X);
        var ey = Convert.ToInt32(e.Y);
        maxX = Math.Max(maxX, ex);
        minX = Math.Min(minX, ex);
        maxY = Math.Max(maxY, ey);
        minY = Math.Min(minY, ey);

        if (xs.TryGetValue(ex, out var points))
        {
            points.Add(ey);
        }
        else
        {
            xs[ex] = new SortedSet<int>() { ey };
        }
    }

    /// Contains a list of points that make up the inside of the shape formed by the
    /// bounds of edgePixels.
    var innerPixels = new List<SKPoint>();
    for (var x = minX; x <= maxX; x++)
    {
        var ys = xs[x];

        /// Find the lowest values along the Y axis, i.e. values
        /// that make up the lower edge of the shape.
        var temp = new SortedSet<int>();
        foreach (var y in ys)
        {
            if (!ys.TryGetValue(y - 1, out var _))
            {
                temp.Add(y);
            }
        }

        var rayCount = 0;
        for (var y = temp.Min; y <= temp.Max; y++)
        {
            if (temp.TryGetValue(y, out var _))
            {
                rayCount++;
            }

            if (rayCount % 2 == 1)
            {
                innerPixels.Add(new SKPoint(x, y));
            }
        }
    }

    innerPixels.AddRange(edgePixels);

    return innerPixels;
}

It was executed on a circular shape having a radius of 2048 pixels. This method identified 12869 points enclosed within its boundary. The location of the shape on the canvas had no effect. Negative coordinates were also calculated and stored in the result. The benchmark only ran the geometric computations. It did not perform any modifications on the image itself.

[Benchmark]
[ArgumentsSource(nameof(LargeDataSource))]
public ICollection<SKPoint> PixelsInsideEdgeCollection(SKPoint[] Edges) => shade.PixelsInsideEdge(Edges);

public static IEnumerable<SKPoint[]> LargeDataSource()
{
    var shade = new BlockShade(SKColor.Empty);

    yield return shade.GetCircleEdge(new SKPoint(0, 0), 2048.0f).ToArray();
}

The results of this benchmark are shown below.

dotnet run -c Release --filter PixelsInsideEdgeCollection --runtimes \
net5.0 net6.0 net7.0

// * Summary *

BenchmarkDotNet=v0.13.4, OS=Windows 11 (10.0.22621.1105)
AMD Ryzen 5 5600H with Radeon Graphics, 1 CPU, 12 logical and 6 physical cores
.NET SDK=7.0.102
[Host] : .NET 5.0.17 (5.0.1722.21314), X64 RyuJIT AVX2
Job-SOHORL : .NET 5.0.17 (5.0.1722.21314), X64 RyuJIT AVX2
Job-PPCKCW : .NET 6.0.13 (6.0.1322.58009), X64 RyuJIT AVX2
Job-EBVIPG : .NET 7.0.2 (7.0.222.60605), X64 RyuJIT AVX2


|           Method |  Runtime |          Edges |     Mean | Ratio |
|----------------- |--------- |--------------- |---------:|------:|
| PixelsInsideEdge | .NET 5.0 | SKPoint[12869] | 217.7 ms |  1.00 |
| PixelsInsideEdge | .NET 6.0 | SKPoint[12869] | 213.2 ms |  0.98 |
| PixelsInsideEdge | .NET 7.0 | SKPoint[12869] | 161.9 ms |  0.75 |

But what does this mean for the performance of the application as a whole? To test this, I ran Doom Fire, which replicates the effect from the title screen of the classic video game. I generated a 5 second animated sequence of images in sizes of 128 × 128, 256 × 128, 512 × 128 and 1024 × 128 pixels.

These three videos show the output of the effect at 128 × 128 pixels (top left), 256 × 128 pixels (top centre), and 512 × 128 pixels (above).

The height of the image was restricted to minimise the amount of empty pixels being pushed during the test. Time elapsed was measured with an instance of System.Diagnostics.Stopwatch. Each test was first run 5 times to warm up the JIT and allow the progressive compiler to thoroughly kick in and optimise the code. The results of these warm-up tests were discarded. Then 3 further iterations were run, and the fastest result was considered for comparison.

|  Runtime |           Size |    Time |
|--------- |---------------:|--------:|
| .NET 5.0 |   128 x 128 px | 13.59 s |
| .NET 5.0 |   256 x 128 px | 13.74 s |
| .NET 5.0 |   512 x 128 px | 25.67 s |
| .NET 5.0 |  1024 x 128 px | 49.17 s |

|  Runtime |           Size |    Time |
|--------- |---------------:|--------:|
| .NET 7.0 |   128 x 128 px | 13.35 s |
| .NET 7.0 |   256 x 128 px | 13.52 s |
| .NET 7.0 |   512 x 128 px | 23.23 s |
| .NET 7.0 |  1024 x 128 px | 44.53 s |

This wasn’t quite as stark an improvement as a standalone microbenchmark. A single method being executed in quick succession has vastly different performance characteristics from a complete application. This benchmark also saved the frame to disk, which adds an I/O penalty. As expected, smaller data sets showed minimal variation. The numbers started diverging as the magnitude of data increased.

Conclusion

Based on the standard benchmarks, .NET 5 and 6 show similar performance. With .NET 5 now out of support, and .NET 7 being earmarked as a short-term support release, developers are likely to upgrade to .NET 6 instead of .NET 7. And .NET 6 has an additional 6 months of support over .NET 7. There are many customers who would accept the tradeoff of slower runtime execution for longer official support. If your application is performance sensitive, it’s a no-brainer that you must move to .NET 7. But even otherwise, if you can risk the shorter support cycle (and .NET 8 will certainly be released by then), it may be a worthwhile investment to consider targeting your application for .NET 7 instead.

Breaking Circular Dependencies in Microsoft DI with Lazy Resolution

Pranav Negandhi

The service locator pattern is understandably looked down upon. I’m not the kind to get swept away with hubris, but injecting a service provider into other classes, and telling them to pick whatever they like out of it is just global variables with more steps.

There are certain cases where this is the most straightforward solution to a problem. But this anti-pattern can still be avoided with a bit of thought. This is a real-world scenario that I faced few months back.

Background

A wizard is a UI pattern that is used to guide the user through the stages of a process (a license key verification and user registration in this case). I wrote a simple application that would lead the user through each step.

  1. Welcome and short instruction note.
  2. License Key Entry and verification.
  3. Registration Form input and validation.
  4. Review form input.
  5. Completion.

But there may be cases when somebody might need to change their license key after it has been entered. For this, the application had a button to go back to the previous screen.

PlantUML Syntax:<br /> @startuml</p> <p>object Welcome<br /> object “License Key Entry” as LicenseKeyEntry</p> <p>object “Registration Form” as RegistrationForm<br /> object Review<br /> object Completed</p> <p>Welcome -down-> LicenseKeyEntry</p> <p>LicenseKeyEntry -right-> RegistrationForm : Next<br /> RegistrationForm -left-> LicenseKeyEntry : Back</p> <p>RegistrationForm -down-> Review : Next<br /> Review -up-> RegistrationForm : Back</p> <p>Review -> Completed : Register</p> <p>@enduml<br />

Each screen was implemented in its own class as a window object. It would be ideal if the screen object would be injected wherever needed through Microsoft Dependency Injection. The Welcome class would receive a reference to License Key Entry, which would receive a reference to the Registration Form, and so on. But some of the screens also needed a reference to the previous screen. Registration Form would require a reference to License Key Entry. Confirmation would require a reference to the Registration Form.

This would create a circular dependency, which is not supported by Microsoft Dependency Injection.

public class LicenseKeyEntry : Form
{
    public LicenseKeyEntry(RegistrationForm next) { … }
}

public class RegistrationForm : Form
{
    public RegistrationForm(LicenseKeyEntry previous, Confirmation next) { … }
}

private static void ConfigureHostServices(HostBuilderContext _, IServiceCollection services)
{
    …
    services.AddSingleton<LicenseKeyEntry>();
    services.AddSingleton<RegistrationForm>(); /// Welp! Circular dependency!
    …
}

System.InvalidOperationException: A circular dependency was detected for the service of type ‘LicenseKeyEntry’.

My first instinct was that this was an impossible problem to solve. Classes need references. References must come from the DI container. The container won’t allow creating circular dependencies between types. Just hand over a reference to the service provider to the objects, and let them ask for whatever objects they need at runtime.

public class RegistrationForm : Form
{
    private IServiceProvider _services;

    /// Don't do this!
    public RegistrationForm(IServiceProvider services)
    {
        _services = services;
    }

    public void Next()
    {
        var next = services.GetRequiredService<Confirmation>();
        …
    }

    public void Previous()
    {
        var previous = services.GetRequiredService<LicenseKeyEntry>();
        …
    }
}

But this reeks of a code smell. The class was now bound to the types in the specific dependency injection framework. Switching over to another framework or removing it altogether would be difficult. Testing and mocking became more complicated, because the unit tests would now have to inject DI container, which would contain the mock types.

A Workaround

While the approach shown above is not advisable, it does demonstrate the strategy of using lazy resolution to break circular dependencies. .NET contains a built-in Lazy<T> type that can be leveraged for the job.

Begin by changing the constructor signatures to use Lazy<T>, where T is the actual type that is required.

public RegistrationForm(Lazy<LicenseKeyEntry> previous, Lazy<Confirmation> next) { … }

Then, inject the Lazy types into the service container.

services.AddSingleton<LicenseKeyEntry>();
services.AddSingleton<RegistrationForm>();
services.AddSingleton<Confirmation>();
services.AddTransient<Lazy<RegistrationForm>>();
services.AddTransient<Lazy<LicenseKeyEntry>>();
services.AddTransient<Lazy<Confirmation>>();

This removes the circular dependency because these types don’t have a direct reference to each other. But it’s important that the value of the dependent types is not realised in the constructor. They should continue to hold a reference to the Lazy<T> type instead, and only reify the underlying instance later down the line.

public class RegistrationForm : Form
{
    private Lazy<LicenseKeyEntry> _previous;
    private Lazy<Confirmation> _next;

    public RegistrationForm(Lazy<LicenseKeyEntry> previous, Lazy<Confirmation> next)
    {
        _previous = previous;
        _next = next;
    }

    public void Next()
    {
        var next = _next.Value;
        …
    }

    public void Previous()
    {
        var previous = _previous.Value;
        …
    }
}

Addendum

Thomas Levesque wrapped this into an elegant implementation that is exposed by a simple extension method on the service collection. The full article is available on his blog.

public static class ServiceCollectionExtensions
{
    public static IServiceCollection AddLazyResolution(this IServiceCollection services)
    {
        return services.AddTransient(typeof(Lazy<>), typeof(LazilyResolved<>));
    }

    private class LazilyResolved<T> : Lazy<T>
    {
        public LazilyResolved(IServiceProvider serviceProvider) : base(serviceProvider.GetRequiredService<T>)
        {
        }
    }
}