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Fix native library loader silently failing when CUDA DLLs are missing #1555

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Fix native library loader silently failing when CUDA DLLs are missing #1555

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340f948
Fix native library loader silently failing when CUDA DLLs are missing
alinpahontu2912 Mar 20, 2026
c7f1271
Fix native library loader silently failing when CUDA DLLs are missing
alinpahontu2912 Mar 20, 2026
f1c93e4
Update src/TorchSharp/Torch.cs
alinpahontu2912 Mar 20, 2026
cf80df3
Merge branch 'fix/cuda-dll-silent-load-failure' of https://github.com…
alinpahontu2912 Mar 20, 2026
2836370
Fix native loader: only LibTorchSharp determines load success
alinpahontu2912 Mar 24, 2026
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5 changes: 4 additions & 1 deletion src/TorchSharp/Tensor/Factories/Tensor.Factories.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -647,7 +647,10 @@ private static void ValidateIntegerRange(long value, ScalarType dtype, string ar
static torch()
{
deleters = new ConcurrentDictionary<TorchSharp.PInvoke.GCHandleDeleter, TorchSharp.PInvoke.GCHandleDeleter>();
TryInitializeDeviceType(DeviceType.CUDA);
if (!TryInitializeDeviceType(DeviceType.CUDA)) {
// CUDA not available, ensure CPU backend is loaded
LoadNativeBackend(false, out _);
}
}
#endregion
}
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45 changes: 26 additions & 19 deletions src/TorchSharp/Torch.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -116,7 +116,7 @@ private static void LoadNativeBackend(bool useCudaBackend, out StringBuilder? tr
trace = null;

if (!alreadyLoaded) {
bool ok;
bool ok = true;
trace = new StringBuilder();
trace.AppendLine($"");
trace.AppendLine($"TorchSharp: LoadNativeBackend: Initialising native backend, useCudaBackend = {useCudaBackend}");
Expand All @@ -134,30 +134,32 @@ private static void LoadNativeBackend(bool useCudaBackend, out StringBuilder? tr
// Preloading these DLLs on windows seems to iron out problems where one native DLL
// requests a load of another through dynamic linking techniques.
//
ok = TryLoadNativeLibraryByName("cudnn_adv64_9", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cudnn_cnn64_9", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cudnn_ops64_9", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cudnn_graph64_9.dll", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cudnn_heuristic64_9.dll", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cudnn_engines_precompiled64_9.dll", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cudnn_engines_runtime_compiled64_9.dll", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("nvrtc-builtins64_128", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("caffe2_nvrtc", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("nvrtc64_120_0", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cublasLt64_12", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cufft64_11", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cusparse64_12", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("cusolver64_11", typeof(torch).Assembly, trace);
// These are optional preloads to help Windows resolve transitive native dependencies.
// Failures here are non-fatal -- the critical loads are torch_cuda and LibTorchSharp below.
TryLoadNativeLibraryByName("cudnn_adv64_9", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cudnn_cnn64_9", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cudnn_ops64_9", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cudnn_graph64_9.dll", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cudnn_heuristic64_9.dll", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cudnn_engines_precompiled64_9.dll", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cudnn_engines_runtime_compiled64_9.dll", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("nvrtc-builtins64_128", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("caffe2_nvrtc", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("nvrtc64_120_0", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cublasLt64_12", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cufft64_11", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cusparse64_12", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("cusolver64_11", typeof(torch).Assembly, trace);
}

ok = TryLoadNativeLibraryByName("torch_cuda", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("torch_cuda", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("LibTorchSharp", typeof(torch).Assembly, trace);
} else {
ok = TryLoadNativeLibraryByName("torch_cpu", typeof(torch).Assembly, trace);
TryLoadNativeLibraryByName("torch_cpu", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("LibTorchSharp", typeof(torch).Assembly, trace);
}

trace.AppendLine($" Result from regular native load of LibTorchSharp is {ok}");
trace.AppendLine($" Result from regular native load of backend libraries (CUDA preloads + torch_* + LibTorchSharp) is {ok}");

// Try dynamic load from package directories
if (!ok) {
Expand Down Expand Up @@ -299,7 +301,12 @@ public static bool TryInitializeDeviceType(DeviceType deviceType)
return false;
}

LoadNativeBackend(deviceType == DeviceType.CUDA, out _);
try {
LoadNativeBackend(deviceType == DeviceType.CUDA, out _);
} catch (NotSupportedException) {
return false;
}

if (deviceType == DeviceType.CUDA) {
return cuda.CallTorchCudaIsAvailable();
} else {
Expand Down