From 23b432f570e4d3bdaf23a657106616b8acf1d7c5 Mon Sep 17 00:00:00 2001
From: Felix Weiglhofer <weiglhofer@fias.uni-frankfurt.de>
Date: Tue, 1 Jul 2025 16:55:10 +0200
Subject: [PATCH] OpenCL: Propagate number of host threads to PoCL runtime.

---
 GPU/GPUTracking/Base/opencl/GPUReconstructionOCL.cxx | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/GPU/GPUTracking/Base/opencl/GPUReconstructionOCL.cxx b/GPU/GPUTracking/Base/opencl/GPUReconstructionOCL.cxx
index ce05e159461e5..49533216869d2 100644
--- a/GPU/GPUTracking/Base/opencl/GPUReconstructionOCL.cxx
+++ b/GPU/GPUTracking/Base/opencl/GPUReconstructionOCL.cxx
@@ -63,6 +63,13 @@ int32_t GPUReconstructionOCL::GPUChkErrInternal(const int64_t error, const char*
 
 int32_t GPUReconstructionOCL::InitDevice_Runtime()
 {
+  // Propagate processing settings to PoCL runtime.
+  // Won't affect other OpenCL runtimes.
+  if (int nThreads = mProcessingSettings->nHostThreads; nThreads > 0) {
+    auto nThreadsStr = std::to_string(nThreads);
+    setenv("POCL_CPU_MAX_CU_COUNT", nThreadsStr.c_str(), 1);
+  }
+
   if (mMaster == nullptr) {
     cl_int ocl_error;
     cl_uint num_platforms;