How to use recursion with ALEA Library in C#

Question

I am trying to convert a recursive algorithm from CPU to GPU using ALEA Library. I get the following errors if I build the code :

"Fody/Alea.CUDA: AOTCompileServer exited unexpectly with exit code -1073741571"

public class GPUModule : ILGPUModule
{
 public GPUModule (GPUModuleTarget target) : base(target)
 {
 }

 [Kernel]  //Same Error whether RecursionTest is another Kernel or not.
 public void RecursionTest(deviceptr<int> a)
 {
   ...
   RecursionTest(a);
 }

 [Kernel]
 public MyKernel(deviceptr<int> a, ...)
 {
   ...
   var a = __shared__.Array<int>(10);
   RecursionTest(Intrinsic.__array_to_ptr<int>(a)); //Error here
 }
 ...
}

I will appreciate if you provide any documentation or link for recursion examples in C# using ALEA Library.

Thanks in advance

Answer 1

You are using Alea GPU 2.x, the newest version is Alea GPU 3.x. (see www.aleagpu.com). With 3.0, I made a test and it works:

using Alea;
using Alea.CSharp;
using NUnit.Framework;

    public static void RecursionTestFunc(deviceptr<int> a)
    {
        if (a[0] == 0)
        {
            a[0] = -1;
        }
        else
        {
            a[0] -= 1;
            RecursionTestFunc(a);
        }
    }

    public static void RecursionTestKernel(int[] a)
    {
        var tid = threadIdx.x;
        var ptr = DeviceFunction.AddressOfArray(a);
        ptr += tid;
        RecursionTestFunc(ptr);
    }

    [Test]
    public static void RecursionTest()
    {
        var gpu = Gpu.Default;
        var host = new[] {1, 2, 3, 4, 5};
        var length = host.Length;
        var dev = gpu.Allocate(host);
        gpu.Launch(RecursionTestKernel, new LaunchParam(1, length), dev);
        var actual = Gpu.CopyToHost(dev);
        var expected = new[] {-1, -1, -1, -1, -1};
        Assert.AreEqual(expected, actual);
        Gpu.Free(dev);
    }