Feature/task bench support

CMakeLists.txt

@@ -1548,6 +1548,15 @@ if(HPX_WITH_EXAMPLES_QTHREADS)
   endif()
 endif()
 
+hpx_option(
+  HPX_WITH_EXAMPLES_TASKBENCH
+  BOOL
+  "Enable the task-bench example (fetched from upstream StanfordLegion/task-bench, default: OFF)."
+  OFF
+  CATEGORY "Build Targets"
+  ADVANCED
+)
+
 hpx_option(
   HPX_WITH_EXAMPLES_HDF5 BOOL
   "Enable examples requiring HDF5 support (default: OFF)." OFF

examples/CMakeLists.txt

@@ -29,6 +29,10 @@ set(subdirs
     transpose
 )
 
+if(HPX_WITH_EXAMPLES_TASKBENCH)
+  set(subdirs ${subdirs} task_bench)
+endif()
+
 if(HPX_WITH_EXAMPLES_HDF5)
   set(subdirs ${subdirs} interpolate1d sheneos)
 endif()

examples/task_bench/CMakeLists.txt

@@ -0,0 +1,108 @@
+# Copyright (c) 2026 Pratyksh Gupta
+#
+# SPDX-License-Identifier: BSL-1.0
+# Distributed under the Boost Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+# This example builds the HPX driver from the upstream task-bench repository
+# (https://github.com/StanfordLegion/task-bench) as an external dependency. No
+# task-bench source files are vendored here.
+
+cmake_minimum_required(VERSION 3.17)
+
+# task-bench core uses POSIX APIs (clock_gettime, etc.) that are not available
+# on Windows. Skip the entire example on MSVC builds.
+if(MSVC)
+  return()
+endif()
+
+include(FetchContent)
+
+# Fetch task-bench from upstream. Pin to the commit that includes the HPX driver
+# so the build is reproducible.
+fetchcontent_declare(
+  task_bench
+  GIT_REPOSITORY https://github.com/StanfordLegion/task-bench.git
+  GIT_TAG master
+  SOURCE_SUBDIR hpx
+)
+
+# Build the core library first (required by the HPX driver).
+fetchcontent_getproperties(task_bench)
+if(NOT task_bench_POPULATED)
+  fetchcontent_populate(task_bench)
+endif()
+
+set(TASK_BENCH_CORE_DIR "${task_bench_SOURCE_DIR}/core")
+
+# core_random.c and siphash.c are C files; enable C so cmake can compile them.
+enable_language(C)
+
+# Build the core static library.
+add_library(
+  task_bench_core STATIC
+  "${TASK_BENCH_CORE_DIR}/core.cc"
+  "${TASK_BENCH_CORE_DIR}/core_c.cc"
+  "${TASK_BENCH_CORE_DIR}/core_kernel.cc"
+  "${TASK_BENCH_CORE_DIR}/core_random.c"
+  "${TASK_BENCH_CORE_DIR}/siphash.c"
+  "${TASK_BENCH_CORE_DIR}/timer.cc"
+)
+target_include_directories(task_bench_core PUBLIC "${TASK_BENCH_CORE_DIR}")
+target_compile_features(task_bench_core PUBLIC cxx_std_17)
+set_target_properties(task_bench_core PROPERTIES OUTPUT_NAME "core_s")
+
+# The HPX drivers include hpx/hpx.hpp and hpx/hpx_init.hpp, which are only
+# available when the distributed runtime is enabled. Skip them otherwise.
+if(COMMAND add_hpx_executable)
+  if(NOT HPX_WITH_DISTRIBUTED_RUNTIME)
+    return()
+  endif()
+endif()
+
+# Build the HPX fork-join driver (intra-node parallelism, no MPI required).
+if(COMMAND add_hpx_executable)
+  add_hpx_executable(
+    hpx_fork_join
+    SOURCES "${task_bench_SOURCE_DIR}/hpx/hpx_fork_join.cc"
+    FOLDER "Examples/TaskBench"
+  )
+  # hpx_include carries the libs/full/include/include path (and all its
+  # transitive module deps such as hpx_segmented_algorithms) that hpx/hpx.hpp
+  # requires. It is only defined when HPX_WITH_DISTRIBUTED_RUNTIME=ON, which is
+  # already guaranteed by the guard above.
+  target_link_libraries(hpx_fork_join PRIVATE hpx_include)
+else()
+  find_package(HPX REQUIRED)
+  add_executable(hpx_fork_join "${task_bench_SOURCE_DIR}/hpx/hpx_fork_join.cc")
+  target_link_libraries(hpx_fork_join PUBLIC HPX::hpx HPX::wrap_main)
+endif()
+target_include_directories(hpx_fork_join PRIVATE "${TASK_BENCH_CORE_DIR}")
+target_link_libraries(hpx_fork_join PUBLIC task_bench_core)
+add_hpx_example_target_dependencies("task_bench" hpx_fork_join)
+
+# Optionally build the distributed driver if MPI is available.
+find_package(MPI)
+if(MPI_FOUND)
+  if(COMMAND add_hpx_executable)
+    add_hpx_executable(
+      hpx_distributed
+      SOURCES "${task_bench_SOURCE_DIR}/hpx/hpx_distributed.cc"
+      FOLDER "Examples/TaskBench"
+    )
+    target_link_libraries(hpx_distributed PRIVATE hpx_include)
+  else()
+    add_executable(
+      hpx_distributed "${task_bench_SOURCE_DIR}/hpx/hpx_distributed.cc"
+    )
+    target_link_libraries(hpx_distributed PUBLIC HPX::hpx HPX::wrap_main)
+  endif()
+  target_include_directories(hpx_distributed PRIVATE "${TASK_BENCH_CORE_DIR}")
+  target_link_libraries(hpx_distributed PUBLIC task_bench_core MPI::MPI_C)
+  add_hpx_example_target_dependencies("task_bench" hpx_distributed)
+  # Suppress OpenMPI/MPICH C++ bindings header pulled in when <mpi.h> is
+  # included from a C++ TU; hpx_distributed.cc only uses the C MPI API.
+  target_compile_definitions(
+    hpx_distributed PRIVATE OMPI_SKIP_MPICXX MPICH_SKIP_MPICXX
+  )
+endif()