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Windows Arm Support #1493

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4ec7d5d
Windows Arm Support
cm4ker Feb 19, 2026
c39acc3
Update src/TorchSharp/Torch.cs
cm4ker Aug 30, 2025
af4f5bd
Update src/TorchSharp/Torch.cs
cm4ker Aug 30, 2025
4b99c29
Fix win-arm64 libtorch SHA for 2.10
cm4ker Feb 19, 2026
a2e4201
Add win-arm64 debug libtorch SHA (2.10)
cm4ker Feb 19, 2026
1b9222a
Restore win-arm64 libtorch 2.7.1 SHA files
cm4ker Feb 19, 2026
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16 changes: 8 additions & 8 deletions Directory.Build.props
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Expand Up @@ -52,17 +52,16 @@
<TargetOS Condition="'$(TargetOS)' == '' AND $([MSBuild]::IsOSPlatform('osx'))">mac</TargetOS>
<TargetOS Condition="'$(TargetOS)' == '' AND '$(OS)' != 'Windows_NT'">linux</TargetOS>


<TargetPlatform Condition="'$(TargetPlatform)' == ''">$(TargetOS)-$(TargetArchitecture)</TargetPlatform>

<TargetRuntimeID Condition="'$(TargetOS)' == 'windows'">win-x64</TargetRuntimeID>
<TargetRuntimeID Condition="'$(TargetOS)' == 'windows' and '$(TargetArchitecture)' == 'arm64'">win-arm64</TargetRuntimeID>
<TargetRuntimeID Condition="'$(TargetOS)' == 'windows' and '$(TargetArchitecture)' != 'arm64'">win-x64</TargetRuntimeID>
<TargetRuntimeID Condition="'$(TargetOS)' == 'linux'">linux-x64</TargetRuntimeID>
<TargetRuntimeID Condition="'$(TargetPlatform)' == 'mac-arm64'">osx-arm64</TargetRuntimeID>

<TargetRuntimeID Condition="'$(TargetOS)' == 'windows'">win-x64</TargetRuntimeID>
<TargetRuntimeID Condition="'$(TargetOS)' == 'linux'">linux-x64</TargetRuntimeID>
<TargetRuntimeID Condition="'$(TargetOS)' == 'mac'">osx-$(TargetArchitecture)</TargetRuntimeID>

<!-- on windows separate debug binaries of LibTorch are available-->
<!-- on windows separate debug binaries of LibTorch are available -->
<LibTorchDebug Condition="('$(NativeConfiguration)' == 'Debug') AND '$(TargetOS)' == 'windows'">-debug</LibTorchDebug>

<NativeOutputPath>$(BaseOutputPath)$(NativeTargetArchitecture).$(NativeConfiguration)\Native\</NativeOutputPath>
Expand Down Expand Up @@ -95,8 +94,8 @@

<PropertyGroup>
<!-- turned on/off manually in separate CI jobs -->
<SkipCuda Condition="'$(TargetOS)' == 'mac'">true</SkipCuda>
<SkipCuda Condition="'$(TargetOS)' != 'mac'">false</SkipCuda>
<SkipCuda Condition="'$(TargetOS)' == 'mac' or ('$(TargetOS)' == 'windows' and '$(TargetArchitecture)' == 'arm64')">true</SkipCuda>
<SkipCuda Condition="'$(SkipCuda)' == ''">false</SkipCuda>
<SkipTests>false</SkipTests>

<!-- By default only TorchSharp and no libtorch-cpu or libtorch-cuda packages are built. The CI file controls these via 'BuildLibTorchPackages' -->
Expand Down Expand Up @@ -141,7 +140,8 @@
<LibTorchCpuLocalNameSuffix>cpu</LibTorchCpuLocalNameSuffix>
<LibTorchCudaLocalNameSuffix>cu$(CudaVersionNoDot)</LibTorchCudaLocalNameSuffix>
<LibTorchArchiveCoreName Condition="'$(TargetOS)' == 'windows'">libtorch-win-shared-with-deps$(LibTorchDebug)</LibTorchArchiveCoreName>
<LibTorchArchiveCoreName Condition="'$(TargetOS)' == 'linux'">libtorch-shared-with-deps</LibTorchArchiveCoreName>
<LibTorchArchiveCoreName Condition="'$(TargetOS)' == 'windows' and '$(TargetArchitecture)' == 'arm64'">libtorch-win-arm64-shared-with-deps$(LibTorchDebug)</LibTorchArchiveCoreName>
<LibTorchArchiveCoreName Condition="'$(TargetOS)' == 'linux'">libtorch-cxx11-abi-shared-with-deps</LibTorchArchiveCoreName>
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Copilot AI Feb 27, 2026

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The LibTorchArchiveCoreName for Linux has been changed to "libtorch-cxx11-abi-shared-with-deps", but there is no corresponding SHA file for the 2.10.0 version (libtorch-cxx11-abi-shared-with-deps-2.10.0%2Bcpu.zip.sha). The repository contains "libtorch-shared-with-deps-2.10.0%2Bcpu.zip.sha" but not the cxx11-abi variant for 2.10.0. This will cause the build to fail when trying to validate the downloaded archive. Either:

  1. The SHA file needs to be added to this PR, or
  2. This change to the Linux archive name should be removed if it was unintentional

This appears to be an unrelated change that was accidentally included in the Windows ARM64 support PR.

Suggested change
<LibTorchArchiveCoreName Condition="'$(TargetOS)' == 'linux'">libtorch-cxx11-abi-shared-with-deps</LibTorchArchiveCoreName>
<LibTorchArchiveCoreName Condition="'$(TargetOS)' == 'linux'">libtorch-shared-with-deps</LibTorchArchiveCoreName>

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<LibTorchArchiveCoreName Condition="'$(TargetOS)' == 'mac'">libtorch-macos-x86_64</LibTorchArchiveCoreName>
<LibTorchArchiveCoreName Condition="'$(TargetPlatform)' == 'mac-arm64'">libtorch-macos-arm64</LibTorchArchiveCoreName>
<LibTorchCpuArchiveBase>$(LibTorchArchiveCoreName)-$(LibTorchVersion)$(LibTorchCpuArchiveNameSuffix)</LibTorchCpuArchiveBase>
Expand Down
25 changes: 22 additions & 3 deletions Directory.Build.targets
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@@ -1,7 +1,12 @@
<Project>

<!-- Ensure NativeOutputPath is populated for consumer projects (examples/tests) on Windows ARM64 by staging redist first -->
<Target Name="EnsureNativeRedistStaged" BeforeTargets="PrepareForRun" Condition="'$(OS)' == 'Windows_NT' and '$(NativeTargetArchitecture)' == 'arm64' and '$(SkipNative)' != 'true'">
<Message Importance="High" Text="Ensuring Windows ARM64 native redist is staged to $(NativeOutputPath)" />
<MSBuild Projects="$(RepoRoot)src\Redist\libtorch-cpu\libtorch-cpu.proj" Targets="Build" Properties="Configuration=$(NativeConfiguration);TargetOS=windows;TargetArchitecture=arm64" />
</Target>

<!-- We copy over the LibTorch native binaries in order to run tests. This can probably be automated better. -->
<!-- These lists are duplicated in redist/... with file splitting added for package prep -->
<!-- These lists are duplicated in redist/... with file splitting added for package prep -->

<ItemGroup Condition="'$(TestUsesLibTorch)' == 'true' and '$(SkipNative)' != 'true' ">
<NativeAssemblyReference Include="LibTorchSharp" />
Expand All @@ -18,6 +23,20 @@
<NativeAssemblyReference Include="uv" />
</ItemGroup>

<!-- Windows ARM64 CPU libtorch binary list used for examples and testing -->
<ItemGroup Condition="'$(NativeTargetArchitecture)' == 'arm64' and '$(OS)' == 'Windows_NT' and '$(TestUsesLibTorch)' == 'true' and ('$(TestCuda)' != 'true' or '$(SkipCuda)' == 'true') and '$(SkipNative)' != 'true' ">
<NativeAssemblyReference Include="aoti_custom_ops" />
<NativeAssemblyReference Include="backend_with_compiler" />
<NativeAssemblyReference Include="c10" />
<NativeAssemblyReference Include="torchbind_test" />
<NativeAssemblyReference Include="torch" />
<NativeAssemblyReference Include="torch_cpu" />
<NativeAssemblyReference Include="torch_global_deps" />
<NativeAssemblyReference Include="uv" />
<NativeAssemblyReference Include="jitbackend_test" />
<NativeAssemblyReference Include="armpl_lp64" />
</ItemGroup>

<!-- Windows CUDA 12.1 libtorch binary list used for examples and testing -->
<ItemGroup Condition="'$(NativeTargetArchitecture)' == 'x64' and '$(OS)' == 'Windows_NT' and '$(TestUsesLibTorch)' == 'true' and ('$(TestCuda)' == 'true' and '$(SkipCuda)' != 'true') and '$(SkipNative)' != 'true' ">
<NativeAssemblyReference Include="c10" Variant="cuda\" />
Expand Down Expand Up @@ -113,5 +132,5 @@
</Copy>

</Target>

</Project>
2 changes: 1 addition & 1 deletion pkg/TorchAudio/TorchAudio.nupkgproj
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Expand Up @@ -8,7 +8,7 @@
<ItemGroup>
<ProjectReference Include="..\TorchSharp\TorchSharp.nupkgproj" />
</ItemGroup>

<ItemGroup>
<Content Include="..\common\NormalPackage.props" Pack="true" PackagePath="buildTransitive\net8.0\$(MSBuildProjectName).props" />
<Content Include="..\common\NormalPackage.targets" Pack="true" PackagePath="buildTransitive\net8.0\$(MSBuildProjectName).targets" />
Expand Down
2 changes: 1 addition & 1 deletion pkg/TorchVision/TorchVision.nupkgproj
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Expand Up @@ -8,7 +8,7 @@
<ItemGroup>
<ProjectReference Include="..\TorchSharp\TorchSharp.nupkgproj" />
</ItemGroup>

<ItemGroup>
<Content Include="..\common\NormalPackage.props" Pack="true" PackagePath="buildTransitive\net8.0\$(MSBuildProjectName).props" />
<Content Include="..\common\NormalPackage.targets" Pack="true" PackagePath="buildTransitive\net8.0\$(MSBuildProjectName).targets" />
Expand Down
16 changes: 16 additions & 0 deletions pkg/libtorch-cpu-win-arm64/libtorch-cpu-win-arm64.nupkgproj
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@@ -0,0 +1,16 @@
<Project Sdk="Microsoft.NET.Sdk" DefaultTargets="Pack">

<PropertyGroup>
<TargetFramework>netstandard2.0</TargetFramework>
</PropertyGroup>

<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
</ItemGroup>

<ItemGroup>
<Content Include="..\common\CpuHeadPackage.props" Pack="true" PackagePath="buildTransitive\netstandard2.0\$(MSBuildProjectName).props" />
<Content Include="..\common\CpuHeadPackage.targets" Pack="true" PackagePath="buildTransitive\netstandard2.0\$(MSBuildProjectName).targets" />
<Content Include="..\empty.txt" Pack="true" PackagePath="lib\netstandard2.0\_._" />
<Content Include="$(RepoRoot)\THIRD-PARTY-NOTICES.txt" Pack="true" PackagePath="LICENSE-LIBTORCH.txt" />
</ItemGroup>
</Project>
1 change: 1 addition & 0 deletions pkg/libtorch-cpu/libtorch-cpu.nupkgproj
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Expand Up @@ -8,6 +8,7 @@
<ProjectReference Include="../libtorch-cpu-linux-x64/libtorch-cpu-linux-x64.nupkgproj" />
<ProjectReference Include="../libtorch-cpu-osx-arm64/libtorch-cpu-osx-arm64.nupkgproj" />
<ProjectReference Include="../libtorch-cpu-win-x64/libtorch-cpu-win-x64.nupkgproj" />
<ProjectReference Include="../libtorch-cpu-win-arm64/libtorch-cpu-win-arm64.nupkgproj" />
</ItemGroup>

<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
Expand Down
6 changes: 4 additions & 2 deletions pkg/pack.proj
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Expand Up @@ -22,8 +22,10 @@
<Target Name="Pack" DependsOnTargets="Restore">
<Warning Text="Packages will be incomplete and unusable on linux platforms. To get a complete package you need the LibTorchSharp.so binaries for other platforms and copy them into '$(PackagePreparationPath)' to make complete packages. This is automated by Azure Pipelines."
Condition="'$(IncludeTorchSharpPackage)' == 'true' AND !Exists('$(PackagePreparationPath)\TorchSharp\runtimes\linux-x64\native\libLibTorchSharp.so')" />
<Warning Text="Packages will be incomplete and unusable on win-x64 platform. To get a complete package you need the LibTorchSharp.dll binaries for other platforms and copy them into '$(PackagePreparationPath)' to make complete packages. This is automated by Azure Pipelines."
Condition="'$(IncludeTorchSharpPackage)' == 'true' AND !Exists('$(PackagePreparationPath)\TorchSharp\runtimes\win-x64\native\LibTorchSharp.dll')" />
<Warning Text="Packages will be incomplete and unusable on win-x64 platform. To get a complete package you need the LibTorchSharp.dll binaries for other platforms and copy them into '$(PackagePreparationPath)' to make complete packages. This is automated by Azure Pipelines."
Condition="'$(IncludeTorchSharpPackage)' == 'true' AND !Exists('$(PackagePreparationPath)\TorchSharp\runtimes\win-x64\native\LibTorchSharp.dll')" />
<Warning Text="Packages will be incomplete and unusable on win-arm64 platform. To get a complete package you need the LibTorchSharp.dll binaries for other platforms and copy them into '$(PackagePreparationPath)' to make complete packages. This is automated by Azure Pipelines."
Condition="'$(IncludeTorchSharpPackage)' == 'true' AND !Exists('$(PackagePreparationPath)\TorchSharp\runtimes\win-arm64\native\LibTorchSharp.dll')" />

<MSBuild Projects="%(PackProject.Identity)" Targets="Pack" />

Expand Down
19 changes: 7 additions & 12 deletions src/Native/build.cmd
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Expand Up @@ -23,6 +23,7 @@ if /i [%1] == [Debug] ( set CMAKE_BUILD_TYPE=Debug&&shift&goto Arg_Loop)
if /i [%1] == [x86] ( set __BuildArch=x86&&set __VCBuildArch=x86&&shift&goto Arg_Loop)
if /i [%1] == [x64] ( set __BuildArch=x64&&set __VCBuildArch=x86_amd64&&shift&goto Arg_Loop)
if /i [%1] == [amd64] ( set __BuildArch=x64&&set __VCBuildArch=x86_amd64&&shift&goto Arg_Loop)
if /i [%1] == [arm64] ( set __BuildArch=arm64&&set __VCBuildArch=x86_arm64&&shift&goto Arg_Loop)

if /i [%1] == [--libtorchpath] ( set LIBTORCH_PATH=%2&&shift&goto Arg_Loop)

Expand Down Expand Up @@ -86,30 +87,24 @@ goto :SetupDirs
:: Setup vars for VS2019
set __PlatformToolset=v142
set __VSVersion=16 2019
if NOT "%__BuildArch%" == "arm64" (
:: Set the environment for the native build
call "%VS160COMNTOOLS%..\..\VC\Auxiliary\Build\vcvarsall.bat" %__VCBuildArch%
)
:: Set the environment for the native build
call "%VS160COMNTOOLS%..\..\VC\Auxiliary\Build\vcvarsall.bat" %__VCBuildArch%
goto :SetupDirs

:VS2017
:: Setup vars for VS2017
set __PlatformToolset=v141
set __VSVersion=15 2017
if NOT "%__BuildArch%" == "arm64" (
:: Set the environment for the native build
call "%VS150COMNTOOLS%..\..\VC\Auxiliary\Build\vcvarsall.bat" %__VCBuildArch%
)
:: Set the environment for the native build
call "%VS150COMNTOOLS%..\..\VC\Auxiliary\Build\vcvarsall.bat" %__VCBuildArch%
goto :SetupDirs

:VS2015
:: Setup vars for VS2015build
set __PlatformToolset=v140
set __VSVersion=14 2015
if NOT "%__BuildArch%" == "arm64" (
:: Set the environment for the native build
call "%VS140COMNTOOLS%..\..\VC\vcvarsall.bat" %__VCBuildArch%
)
:: Set the environment for the native build
call "%VS140COMNTOOLS%..\..\VC\vcvarsall.bat" %__VCBuildArch%

:SetupDirs
:: Setup to cmake the native components
Expand Down
1 change: 1 addition & 0 deletions src/Native/gen-buildsys-win.bat
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Expand Up @@ -30,6 +30,7 @@ popd
:: Set the target architecture to a format cmake understands.
if /i "%3" == "x64" (set __ExtraCmakeParams=%__ExtraCmakeParams% -A x64)
if /i "%3" == "x86" (set __ExtraCmakeParams=%__ExtraCmakeParams% -A Win32)
if /i "%3" == "arm64" (set __ExtraCmakeParams=%__ExtraCmakeParams% -A ARM64)

echo "%CMakePath%" "-DCMAKE_BUILD_TYPE=%CMAKE_BUILD_TYPE%" "-DCMAKE_INSTALL_PREFIX=%__CMakeBinDir%" "-DLIBTORCH_PATH=%LIBTORCH_PATH%" -G "Visual Studio %__VSString%" %__ExtraCmakeParams% -B. -H%1
"%CMakePath%" "-DCMAKE_BUILD_TYPE=%CMAKE_BUILD_TYPE%" "-DCMAKE_INSTALL_PREFIX=%__CMakeBinDir%" "-DLIBTORCH_PATH=%LIBTORCH_PATH%" -G "Visual Studio %__VSString%" %__ExtraCmakeParams% -B. -H%1
Expand Down
16 changes: 15 additions & 1 deletion src/Redist/libtorch-cpu/libtorch-cpu.proj
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Expand Up @@ -30,7 +30,8 @@
<CopyToPackageSemaphore>$(MainPackageFolder)\.copied.SkipTests.$(SkipTests).IncludeLibTorchCpuPackages.$(IncludeLibTorchCpuPackages)</CopyToPackageSemaphore>
</PropertyGroup>

<ItemGroup Condition="'$(TargetOS)' == 'windows'">
<ItemGroup Condition="'$(TargetOS)' == 'windows' and '$(NativeTargetArchitecture)' != 'arm64'">
<File Include="libtorch\lib\asmjit.dll" />
<File Include="libtorch\lib\c10.dll" />
<File Include="libtorch\lib\libiomp5md.dll" />
<File Include="libtorch\lib\libiompstubs5md.dll" />
Expand All @@ -39,6 +40,19 @@
<File Include="libtorch\lib\torch_global_deps.dll" />
<File Include="libtorch\lib\uv.dll" />
</ItemGroup>
<!-- Windows ARM64 has a smaller set of DLLs and different deps names -->
<ItemGroup Condition="'$(TargetOS)' == 'windows' and '$(NativeTargetArchitecture)' == 'arm64'">
<File Include="lib\aoti_custom_ops.dll"/>
<File Include="lib\backend_with_compiler.dll"/>
<File Include="lib\c10.dll"/>
<File Include="lib\jitbackend_test.dll"/>
<File Include="lib\torchbind_test.dll"/>
<File Include="lib\torch.dll"/>
<File Include="lib\torch_cpu.dll"/>
<File Include="lib\torch_global_deps.dll"/>
<File Include="lib\uv.dll"/>
<File Include="lib\armpl_lp64.dll"/>
Comment on lines +45 to +54
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Copilot AI Feb 27, 2026

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The Windows ARM64 file paths use "lib" instead of "libtorch\lib" which is inconsistent with the x64 Windows paths (lines 34-41) and other platforms. This inconsistency suggests these files may be in a different directory structure in the ARM64 libtorch distribution. Please verify that the ARM64 libtorch archive actually has files directly in a "lib" folder rather than "libtorch\lib". If the directory structure is indeed different, this is correct. Otherwise, these paths should be updated to match the pattern used for other platforms.

Suggested change
<File Include="lib\aoti_custom_ops.dll"/>
<File Include="lib\backend_with_compiler.dll"/>
<File Include="lib\c10.dll"/>
<File Include="lib\jitbackend_test.dll"/>
<File Include="lib\torchbind_test.dll"/>
<File Include="lib\torch.dll"/>
<File Include="lib\torch_cpu.dll"/>
<File Include="lib\torch_global_deps.dll"/>
<File Include="lib\uv.dll"/>
<File Include="lib\armpl_lp64.dll"/>
<File Include="libtorch\lib\aoti_custom_ops.dll"/>
<File Include="libtorch\lib\backend_with_compiler.dll"/>
<File Include="libtorch\lib\c10.dll"/>
<File Include="libtorch\lib\jitbackend_test.dll"/>
<File Include="libtorch\lib\torchbind_test.dll"/>
<File Include="libtorch\lib\torch.dll"/>
<File Include="libtorch\lib\torch_cpu.dll"/>
<File Include="libtorch\lib\torch_global_deps.dll"/>
<File Include="libtorch\lib\uv.dll"/>
<File Include="libtorch\lib\armpl_lp64.dll"/>

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</ItemGroup>
<ItemGroup Condition="'$(NativeTargetArchitecture)' == 'arm64' and '$(TargetOS)' == 'mac'">
<File Include="libtorch\lib\libc10.dylib" />
<File Include="libtorch\lib\libshm.dylib" />
Expand Down
1 change: 1 addition & 0 deletions src/Redist/libtorch-cpu/libtorch-win-arm64-shared-with-deps-2.10.0%2Bcpu.zip.sha
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38D666A9030BA098D1AC5DABFD995CF3D113A12D512252080978B0CC206AF205
1 change: 1 addition & 0 deletions src/Redist/libtorch-cpu/libtorch-win-arm64-shared-with-deps-2.7.1%2Bcpu.zip.sha
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F9DD47C792C900601F08265DDC0186036E01503ADA7895F0C7C90F8AF64FBC4B
1 change: 1 addition & 0 deletions src/Redist/libtorch-cpu/libtorch-win-arm64-shared-with-deps-debug-2.10.0%2Bcpu.zip.sha
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A6B6C3D9FF25113F8E48F6C7A5DD14EFCA5BCA6DE300DE0BD003FCC309439F2C
1 change: 1 addition & 0 deletions src/Redist/libtorch-cpu/libtorch-win-arm64-shared-with-deps-debug-2.7.1%2Bcpu.zip.sha
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DFDD2BECA32B1B3D4894EFA801DC60570849F0ED47A318734BA798A5C4D6513B
51 changes: 46 additions & 5 deletions src/TorchSharp/Torch.cs
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Expand Up @@ -38,13 +38,13 @@ public static partial class torch
RuntimeInformation.OSArchitecture == Architecture.Arm64;

static string nativeRid =>
RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? $"win-x64" :
RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ($"win-{(RuntimeInformation.OSArchitecture == Architecture.Arm64 ? "arm64" : "x64")}") :
RuntimeInformation.IsOSPlatform(OSPlatform.Linux) ? $"linux-x64" :
isAppleSilicon ? "osx-arm64" :
"any";

static string nativeGlob =>
RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? @".*\.dll" :
RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? @".*\.dll$" :
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The regex pattern change adds a "$" end-of-string anchor to the Windows DLL pattern. However, at line 320 in the same file, this pattern is already wrapped with "^" and "$" anchors: var nativeRegExp = new Regex("^" + nativeGlob + "$");. This means the final regex will be ^.*\.dll$$ with a double dollar sign, which is incorrect and will fail to match DLL files. The "$" should be removed from the nativeGlob definition since it's already added when the regex is constructed.

Suggested change
RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? @".*\.dll$" :
RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? @".*\.dll" :

Copilot uses AI. Check for mistakes.
RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? @".*\.dylib\.*" :
// must match
// lib.so
Expand Down Expand Up @@ -129,7 +129,8 @@ private static void LoadNativeBackend(bool useCudaBackend, out StringBuilder? tr

if (useCudaBackend) {
var isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
if (isWindows) {
// CUDA is not supported on Windows ARM64. Only attempt to load CUDA components on Windows x64.
if (isWindows && RuntimeInformation.OSArchitecture == Architecture.X64) {
trace.AppendLine($" Try loading Windows cuda native components");
// Preloading these DLLs on windows seems to iron out problems where one native DLL
// requests a load of another through dynamic linking techniques.
Expand All @@ -152,9 +153,49 @@ private static void LoadNativeBackend(bool useCudaBackend, out StringBuilder? tr

ok = TryLoadNativeLibraryByName("torch_cuda", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("LibTorchSharp", typeof(torch).Assembly, trace);

// On Windows, also attempt direct absolute-path loads from the assembly directory
if (!ok && isWindows) {
var asmDir = Path.GetDirectoryName(typeof(torch).Assembly.Location)!;
var torchCudaPath = Path.Combine(asmDir, "torch_cuda.dll");
var libTorchSharpPath = Path.Combine(asmDir, "LibTorchSharp.dll");
trace.AppendLine($" Attempting absolute-path load of native components from {asmDir}...");
ok = TryLoadNativeLibraryFromFile(torchCudaPath, trace);
if (ok) ok = TryLoadNativeLibraryFromFile(libTorchSharpPath, trace);
}
} else {
ok = TryLoadNativeLibraryByName("torch_cpu", typeof(torch).Assembly, trace);
ok = TryLoadNativeLibraryByName("LibTorchSharp", typeof(torch).Assembly, trace);
var isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
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The variable isWindows is redeclared here when it's already available from line 129. Consider reusing the existing variable to avoid duplication.

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if (isWindows) {
// Preload dependency chain explicitly on Windows: torch_global_deps -> c10 -> uv -> torch -> torch_cpu -> LibTorchSharp
trace.AppendLine($" Try loading Windows CPU native dependency chain: torch_global_deps -> c10 -> uv -> torch -> torch_cpu -> LibTorchSharp");
ok = TryLoadNativeLibraryByName("torch_global_deps", typeof(torch).Assembly, trace);
if (ok) ok = TryLoadNativeLibraryByName("c10", typeof(torch).Assembly, trace);
if (ok) ok = TryLoadNativeLibraryByName("uv", typeof(torch).Assembly, trace);
if (ok) ok = TryLoadNativeLibraryByName("torch", typeof(torch).Assembly, trace);
if (ok) ok = TryLoadNativeLibraryByName("torch_cpu", typeof(torch).Assembly, trace);
if (ok) ok = TryLoadNativeLibraryByName("LibTorchSharp", typeof(torch).Assembly, trace);
} else {
ok = TryLoadNativeLibraryByName("torch_cpu", typeof(torch).Assembly, trace);
if (ok) ok = TryLoadNativeLibraryByName("LibTorchSharp", typeof(torch).Assembly, trace);
}
Comment on lines +167 to +180
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The new Windows CPU dependency loading chain is more explicit (torch_global_deps -> c10 -> uv -> torch -> torch_cpu -> LibTorchSharp) compared to the previous simpler approach that only loaded torch_cpu and LibTorchSharp. While this may be necessary for Windows ARM64, applying it to all Windows platforms (including x64) could be a breaking change. Consider:

  1. Whether this change is actually needed for Windows x64 or only for ARM64
  2. If this is needed for all Windows, testing on x64 to ensure backward compatibility
  3. Whether the order of dependencies is correct for all scenarios

If this change is specifically for ARM64 dependencies, consider adding a condition to only use this explicit chain for ARM64, or add a comment explaining why this is now needed for all Windows platforms.

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// On Windows, also attempt direct absolute-path loads from the assembly directory
if (!ok && isWindows) {
var asmDir = Path.GetDirectoryName(typeof(torch).Assembly.Location)!;
var torchGlobalDepsPath = Path.Combine(asmDir, "torch_global_deps.dll");
var c10Path = Path.Combine(asmDir, "c10.dll");
var uvPath = Path.Combine(asmDir, "uv.dll");
var torchPath = Path.Combine(asmDir, "torch.dll");
var torchCpuPath = Path.Combine(asmDir, "torch_cpu.dll");
var libTorchSharpPath = Path.Combine(asmDir, "LibTorchSharp.dll");
trace.AppendLine($" Attempting absolute-path load of native components from {asmDir}...");
ok = TryLoadNativeLibraryFromFile(torchGlobalDepsPath, trace);
if (ok) ok = TryLoadNativeLibraryFromFile(c10Path, trace);
if (ok) ok = TryLoadNativeLibraryFromFile(uvPath, trace);
if (ok) ok = TryLoadNativeLibraryFromFile(torchPath, trace);
if (ok) ok = TryLoadNativeLibraryFromFile(torchCpuPath, trace);
if (ok) ok = TryLoadNativeLibraryFromFile(libTorchSharpPath, trace);
}
Comment on lines +182 to +198
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Copilot AI Feb 27, 2026

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The absolute-path fallback loading for Windows CPU mode loads files even if earlier named-based loads succeeded (the check is if (!ok && isWindows)). However, this fallback will only execute if the previous named-based loads failed. The logic constructs paths for all dependency DLLs and attempts to load them in order. If any single load fails, the entire chain fails (the pattern if (ok) ok = ... means subsequent loads only happen if previous ones succeeded).

Consider whether this is the desired behavior, or if it should continue attempting to load remaining DLLs even if one fails, similar to how the named-based approach uses ok = ... without checking previous success for each individual library.

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}

trace.AppendLine($" Result from regular native load of LibTorchSharp is {ok}");
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