From 064f7f7bbaab06052c204507f3ac4bd6fbe0034b Mon Sep 17 00:00:00 2001
From: Xavier Valls Pla <xavier.valls.pla@cern.ch>
Date: Tue, 12 Jan 2021 14:18:05 +0100
Subject: [PATCH] test the interactions between IMT and tbb::global_control

---
 core/imt/test/CMakeLists.txt           |  2 +-
 core/imt/test/testTBBGlobalControl.cxx | 55 ++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 core/imt/test/testTBBGlobalControl.cxx

diff --git a/core/imt/test/CMakeLists.txt b/core/imt/test/CMakeLists.txt
index c42fd22921379..6a2beb9568385 100644
--- a/core/imt/test/CMakeLists.txt
+++ b/core/imt/test/CMakeLists.txt
@@ -4,4 +4,4 @@
 # For the licensing terms see $ROOTSYS/LICENSE.
 # For the list of contributors see $ROOTSYS/README/CREDITS.
 
-ROOT_ADD_GTEST(testImt testRTaskArena.cxx testTFuture.cxx testTTaskGroup.cxx LIBRARIES Imt ${TBB_LIBRARIES})
+ROOT_ADD_GTEST(testImt testRTaskArena.cxx testTBBGlobalControl.cxx testTFuture.cxx testTTaskGroup.cxx LIBRARIES Imt ${TBB_LIBRARIES})
diff --git a/core/imt/test/testTBBGlobalControl.cxx b/core/imt/test/testTBBGlobalControl.cxx
new file mode 100644
index 0000000000000..b1d7756335953
--- /dev/null
+++ b/core/imt/test/testTBBGlobalControl.cxx
@@ -0,0 +1,55 @@
+#include "TROOT.h"
+#include "ROOT/RTaskArena.hxx"
+#include "ROOT/TThreadExecutor.hxx"
+#include "ROOTUnitTestSupport.h"
+#include "gtest/gtest.h"
+#include "tbb/global_control.h"
+
+#ifdef R__USE_IMT
+
+const unsigned maxConcurrency = ROOT::Internal::LogicalCPUBandwithControl();
+
+TEST(TBBGlobalControl, RTaskArena)
+{
+   if (maxConcurrency <= 1)
+      return; // skip this test on systems with only 1 core
+   auto gTAInstance = ROOT::Internal::GetGlobalTaskArena(maxConcurrency);
+   tbb::global_control c(tbb::global_control::max_allowed_parallelism, 1u);
+   gTAInstance.reset();
+   ROOT_EXPECT_WARNING(gTAInstance = ROOT::Internal::GetGlobalTaskArena(maxConcurrency);,
+                       "RTaskArenaWrapper",
+                       "tbb::global_control is active, limiting the number of parallel workers"
+                       "from this task arena available for execution.");
+}
+
+TEST(TBBGlobalControl, TThreadExecutor)
+{
+   // ***See them pass***
+   ROOT::TThreadExecutor executor{maxConcurrency};
+   executor.Map([]() { return 1; }, 10); // ParallelFor
+   std::vector<double> vd{0., 1., 2.};
+   executor.Reduce(vd, std::plus<double>{}); // ParallelReduce double
+   std::vector<float> vf{0., 1., 2.};
+   executor.Reduce(vf, std::plus<float>{}); // ParallelReduce float
+
+   tbb::global_control c(tbb::global_control::max_allowed_parallelism, 1u);
+
+   if (maxConcurrency <= 1)
+      return; // skip this test on systems with only 1 core
+   // ***See them warn***
+   ROOT_EXPECT_WARNING(executor.Map([]() { return 1; }, 10), "TThreadExecutor::ParallelFor",
+                       "tbb::global_control is limiting the number of parallel workers."
+                       " Proceeding with 1 threads this time");
+
+   // ParallelReduce double
+   ROOT_EXPECT_WARNING(executor.Reduce(vd, std::plus<double>{}), "TThreadExecutor::ParallelReduce",
+                       "tbb::global_control is limiting the number of parallel workers."
+                       " Proceeding with 1 threads this time");
+
+   // ParallelReduce float
+   ROOT_EXPECT_WARNING(executor.Reduce(vf, std::plus<float>{}), "TThreadExecutor::ParallelReduce",
+                       "tbb::global_control is limiting the number of parallel workers."
+                       " Proceeding with 1 threads this time");
+}
+
+#endif