Minimal Windows CI Build requirements by coatless · Pull Request #27 · coatless-rpkg/rcppbandicoot

coatless · 2025-12-28T06:29:24Z

In this PR, we add in OpenCL headers for windows as well as the prebuilt CLBlast binaries.

By default, the GitHub action runner for Windows does not have a GPU; however, the CPU instruction set should hopefully take. We'll know soon enough. Worst case scenario this is the basis for a community call for help.

To get this to work, we've added:

configure.win
src/Makevars.win

Then, updated the GitHub actions worker to install OpenCL + CLBlast directly. We may switch this over to chocolate.

…ast (though, chocolatey looks better ever second...)

…y to force add to Windows Path

Refactor OpenCL installation steps for Windows and remove verification step.

Updated the R-CMD-check workflow to include Intel OpenCL installation steps for Windows and removed macOS and Ubuntu configurations.

Updated OpenCL environment variables and added debugging step.

Update path format for vcpkg installation on Windows.

Added environment variable registrations for CLBlast.

…itutions

coatless · 2026-01-05T20:03:39Z

RcppBandicoot compiling cleanly on Windows using the OpenCL backend with CLBlast and Intel OpenCL CPU Emulation

Welp, that was fun... I may throw this into a setup-opencl action.

Copilot

Pull request overview

This PR adds Windows CI build support to RcppBandicoot by implementing a Windows-specific configuration system that detects and configures OpenCL and CLBlast dependencies via environment variables.

Introduces configure.win shell script for Windows build configuration
Adds templated Makevars.win.in that gets processed by configure.win
Updates GitHub Actions workflow to install OpenCL SDK and Intel CPU runtime on Windows

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
configure.win	New Windows configuration script that detects OpenCL/CLBlast from environment variables and generates Makevars.win and R/flags.R
src/Makevars.win.in	Template file for Windows-specific compiler and linker flags, processed by configure.win
src/Makevars.win	Removed static version in favor of generated file from template
src/.gitignore	Added Makevars and Makevars.win to ignore list since they are now generated files
.github/workflows/R-CMD-check.yaml	Added Windows build steps: vcpkg installation of OpenCL/CLBlast, Intel OpenCL runtime installation, and registry configuration
.gitattributes	Ensures shell scripts and configure files use LF line endings for cross-platform compatibility
.Rbuildignore	Excludes install.log and .gitattributes from R package builds

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Copilot · 2026-01-05T20:12:07Z

.github/workflows/R-CMD-check.yaml

+          REG ADD "HKLM\SOFTWARE\Khronos\OpenCL\Vendors" /v $dllPath /t REG_DWORD /d 0 /f
+          REG ADD "HKLM\SOFTWARE\Wow6432Node\Khronos\OpenCL\Vendors" /v $dllPath /t REG_DWORD /d 0 /f


Potential security risk: Registry modifications using REG ADD require elevated privileges and should verify success. These commands modify HKLM (HKEY_LOCAL_MACHINE) which typically requires administrator rights. If the commands fail silently, OpenCL runtime won't be properly registered. Add error checking after each REG ADD command to ensure they succeeded, or wrap them in a try-catch block with appropriate error handling.

configure.win

Copilot · 2026-01-05T20:12:09Z

configure.win

+OPENCL_TARGET_VERSION=300
+
+## Kernel source directory (matches configure.ac logic)
+BANDICOOT_KERNELS_DIR=$("${R_HOME}/bin/Rscript" -e 'cat(paste(head(.libPaths(),1), "RcppBandicoot", "include", "bandicoot_bits", "ks", "", sep="/"))')


Multiple issues with BANDICOOT_KERNELS_DIR path handling: (1) The path uses forward slashes from R (sep="/") but is being used on Windows where backslashes are native; (2) No validation that the Rscript command succeeded or returned a valid path; (3) The path may contain spaces or special characters that will break sed substitution on line 109. Consider: validating the path exists, using normalizePath() in R for proper Windows path handling, and escaping special sed characters before substitution.

Suggested change

BANDICOOT_KERNELS_DIR=$("${R_HOME}/bin/Rscript" -e 'cat(paste(head(.libPaths(),1), "RcppBandicoot", "include", "bandicoot_bits", "ks", "", sep="/"))')

BANDICOOT_KERNELS_DIR=$("${R_HOME}/bin/Rscript" -e 'p <- file.path(head(.libPaths(), 1L), "RcppBandicoot", "include", "bandicoot_bits", "ks"); p <- normalizePath(p, winslash="\\", mustWork=FALSE); if (dir.exists(p)) cat(p)')

if [ $? -ne 0 ] || [ -z "${BANDICOOT_KERNELS_DIR}" ] || [ ! -d "${BANDICOOT_KERNELS_DIR}" ]; then

echo "ERROR: Could not determine BANDICOOT_KERNELS_DIR"

exit 1

fi

Copilot · 2026-01-05T20:12:09Z

.github/workflows/R-CMD-check.yaml

+          #- {os: macos-latest,   r: 'release'}
+          #- {os: ubuntu-latest,   r: 'release'}


The macOS and Ubuntu build configurations are commented out, leaving only Windows enabled. While the PR description mentions this is for testing Windows builds, this should not be committed to the main branch as it disables CI testing for other platforms. Either re-enable these platforms once Windows testing is complete, or add a clear TODO comment explaining when they will be re-enabled.

Copilot · 2026-01-05T20:12:10Z

.github/workflows/R-CMD-check.yaml

+      - name: Install Intel CPU Runtime for OpenCL (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          # Download
+          curl -o opencl-installer.exe "${{ env.INTEL_OPENCL_URL }}"
+
+          # Extract MSI from the self-extracting exe
+          $proc = Start-Process "./opencl-installer.exe" "-s -x -f extracted" -NoNewWindow -PassThru
+          $proc.WaitForExit()
+
+          # Install via msiexec
+          $msi = Get-ChildItem ./extracted/*.msi | Select-Object -First 1
+          $proc = Start-Process "msiexec" "/i `"$msi`" /qn /l*! install.log" -NoNewWindow -PassThru
+          $proc.WaitForExit()
+
+          if ($proc.ExitCode -ne 0) {
+            Get-Content install.log
+            exit $proc.ExitCode
+          }
+
+          Remove-Item -Recurse -Force extracted, opencl-installer.exe


The cache step is configured but never checked for a cache hit. The Intel OpenCL Runtime installation (lines 77-98) runs unconditionally, even if the cache was restored. This wastes build time re-installing when the cache is available. Add a condition like "if: runner.os == 'Windows' && steps.cache-opencl-win.outputs.cache-hit != 'true'" to the installation step.

.Rbuildignore

Copilot · 2026-01-05T20:12:10Z

configure.win

+if [ "${HAVE_OPENCL}" = "0" ]; then
+    echo ""
+    echo "WARNING: No GPU backend detected!"
+    echo ""
+    echo "RcppBandicoot requires OpenCL headers to compile on Windows."
+    echo "Set the following environment variables before building:"
+    echo ""
+    echo "  OPENCL_CPPFLAGS  - Path to OpenCL headers (e.g., -IC:/OpenCL/include)"
+    echo "  OPENCL_LIBS      - OpenCL library flags (e.g., -LC:/OpenCL/lib -lOpenCL)"
+    echo "  CLBLAST_CPPFLAGS - Path to CLBlast headers (optional)"
+    echo "  CLBLAST_LIBS     - CLBlast library flags (optional)"
+    echo ""
+fi


The script continues to generate R/flags.R even when OpenCL is not detected (HAVE_OPENCL=0). While this may be intentional to allow builds without GPU support, the warning message on lines 82-93 suggests OpenCL is required ("RcppBandicoot requires OpenCL headers to compile on Windows"). This is contradictory. Either the script should exit with an error when HAVE_OPENCL=0, or the warning message should be softened to indicate GPU features will be unavailable but the build can continue.

Copilot · 2026-01-05T20:12:11Z

configure.win

+    sed -e "s|@BANDICOOT_CXXFLAGS@|${BANDICOOT_CXXFLAGS}|g" \
+        -e "s|@BANDICOOT_LIBS@|${BANDICOOT_LIBS}|g" \
+        -e "s|@OPENMP_CXXFLAGS@|${OPENMP_CXXFLAGS}|g" \
+        -e "s|@OPENCL_TARGET_VERSION@|${OPENCL_TARGET_VERSION}|g" \
+        -e "s|@BANDICOOT_KERNELS_DIR@|${BANDICOOT_KERNELS_DIR}|g" \
+        src/Makevars.win.in > src/Makevars.win


The sed substitution does not escape special sed characters that may appear in the variable values. If BANDICOOT_KERNELS_DIR or other paths contain characters like '&', '', or '/', the sed command will fail or produce incorrect output. The '/' is especially problematic since Windows paths converted from backslashes often use it. Consider escaping these characters before substitution or using a different templating approach.

src/Makevars.win.in

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

coatless and others added 19 commits December 28, 2025 00:26

Minimal Windows CI Build requirements

feb3d90

Are we shipping configure.win?

6cb3060

Downloaded windows?

1786428

Mirror suggested deployment by using vcpkg and custom tooling on CLBl…

3f136a4

…ast (though, chocolatey looks better ever second...)

Clarify linking

e843c34

Use chocolately to grab the intel cpu emulation.

36d0799

Add a _lot_ more debug statements. Move OpenCL Emulation to front. Tr…

98c6b1a

…y to force add to Windows Path

Update R-CMD-check.yaml

de1c81f

Simplify OpenCL installation in R-CMD-check workflow

8967f88

Refactor OpenCL installation steps for Windows and remove verification step.

Simplify installation commands in R-CMD-check.yaml

89fae3a

Modify R-CMD-check.yaml for Windows OpenCL setup

fca36f2

Updated the R-CMD-check workflow to include Intel OpenCL installation steps for Windows and removed macOS and Ubuntu configurations.

Modify OpenCL paths and add debug step

5ea7992

Updated OpenCL environment variables and added debugging step.

Fix vcpkg path to use forward slashes

3226f6b

Update path format for vcpkg installation on Windows.

Register CLBlast locations in workflow

2b6db80

Added environment variable registrations for CLBlast.

Install clblast alongside OpenCL SDK on Windows

b934a04

missing clblast.dll and OpenCL.dll ?

bba0ece

generate R/flags.R from R/flags.R.in with all required variable subst…

cfc9252

…itutions

Remove non-portable flag.

823a2c1

Standardize line endings to avoid complaints from the Windows CI runs...

a5231d5

coatless requested a review from Copilot January 5, 2026 20:05

Copilot started reviewing on behalf of coatless January 5, 2026 20:06 View session

Copilot AI reviewed Jan 5, 2026

View reviewed changes

coatless and others added 4 commits January 6, 2026 01:08

Update configure.win

567be6d

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Update configure.win

f6af274

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Update .Rbuildignore

e001f02

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Update src/Makevars.win.in

6bc4b96

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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Minimal Windows CI Build requirements#27

Minimal Windows CI Build requirements#27
coatless wants to merge 23 commits intomainfrom
i21-windows-support

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		REG ADD "HKLM\SOFTWARE\Khronos\OpenCL\Vendors" /v $dllPath /t REG_DWORD /d 0 /f
		REG ADD "HKLM\SOFTWARE\Wow6432Node\Khronos\OpenCL\Vendors" /v $dllPath /t REG_DWORD /d 0 /f

-BANDICOOT_KERNELS_DIR=$("${R_HOME}/bin/Rscript" -e 'cat(paste(head(.libPaths(),1), "RcppBandicoot", "include", "bandicoot_bits", "ks", "", sep="/"))')
+BANDICOOT_KERNELS_DIR=$("${R_HOME}/bin/Rscript" -e 'p <- file.path(head(.libPaths(), 1L), "RcppBandicoot", "include", "bandicoot_bits", "ks"); p <- normalizePath(p, winslash="\\", mustWork=FALSE); if (dir.exists(p)) cat(p)')
+if [ $? -ne 0 ] || [ -z "${BANDICOOT_KERNELS_DIR}" ] || [ ! -d "${BANDICOOT_KERNELS_DIR}" ]; then
+    echo "ERROR: Could not determine BANDICOOT_KERNELS_DIR"
+    exit 1
+fi

		#- {os: macos-latest, r: 'release'}
		#- {os: ubuntu-latest, r: 'release'}

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