Switch from Thrust to NVIDIA CCCL

Thrust is deprecated, and has been replaced by CCCL.

CMakeLists.txt

@@ -117,7 +117,7 @@ if( TRACCC_SETUP_EIGEN3 )
    endif()
 endif()
 
-# Set up Thrust.
+# Set up CCCL.
 option( TRACCC_SETUP_THRUST
    "Set up the Thrust target(s) explicitly" TRUE )
 option( TRACCC_USE_SYSTEM_THRUST
@@ -127,7 +127,7 @@ if( TRACCC_SETUP_THRUST )
    if( TRACCC_USE_SYSTEM_THRUST )
       find_package( Thrust REQUIRED )
    else()
-      add_subdirectory( extern/thrust )
+      add_subdirectory( extern/cccl )
    endif()
 endif()
 # Set up an IMPORTED library on top of the Thrust library/libraries. One that

extern/cccl/CMakeLists.txt

@@ -0,0 +1,46 @@
+# TRACCC library, part of the ACTS project (R&D line)
+#
+# (c) 2021-2024 CERN for the benefit of the ACTS project
+#
+# Mozilla Public License Version 2.0
+
+# CMake include(s).
+cmake_minimum_required( VERSION 3.14 )
+include( FetchContent )
+
+# Silence FetchContent warnings with CMake >=3.24.
+if( POLICY CMP0135 )
+   cmake_policy( SET CMP0135 NEW )
+endif()
+
+# Tell the user what's happening.
+message( STATUS "Building CCCL as part of the TRACCC project" )
+
+# Declare where to get Thrust from.
+set( TRACCC_CCCL_SOURCE
+   "GIT_REPOSITORY;https://github.com/stephenswat/cccl.git;GIT_TAG;build/allow_installing_when_downstream"
+   CACHE STRING "Source for CCCL, when built as part of this project" )
+mark_as_advanced( TRACCC_CCCL_SOURCE )
+FetchContent_Declare( CCCL ${TRACCC_CCCL_SOURCE} )
+
+# There are a few things to configure here... May not all be necessary but
+# can't hurt.
+set ( CCCL_ENABLE_INSTALL_RULES ON CACHE BOOL "Install CCCL as part of traccc." )
+set ( THRUST_ENABLE_INSTALL_RULES ON CACHE BOOL "Install Thrust as part of traccc." )
+set ( CUB_ENABLE_INSTALL_RULES ON CACHE BOOL "Install CUB as part of traccc." )
+set ( libcudacxx_ENABLE_INSTALL_RULES ON CACHE BOOL "Install libcudacxx as part of traccc." )
+set ( CCCL_ENABLE_LIBCUDACXX ON CACHE BOOL "Disable libcudacxx" )
+set ( CCCL_ENABLE_CUB ON CACHE BOOL "Enable CUB" )
+set ( CCCL_ENABLE_THRUST ON CACHE BOOL "Enable Thrust" )
+set ( CCCL_ENABLE_TESTING OFF CACHE BOOL "Disable CCCL tests" )
+set ( CCCL_ENABLE_EXAMPLES OFF CACHE BOOL "Disable CCCL examples" )
+set ( CCCL_ENABLE_BENCHMARKS OFF CACHE BOOL "Disable CCCL benchmarks" )
+set ( THRUST_ENABLE_TESTING OFF CACHE BOOL "Disable Thrust tests" )
+set ( THRUST_ENABLE_EXAMPLES OFF CACHE BOOL "Disable Thrust examples" )
+set ( THRUST_ENABLE_HEADER_TESTING OFF CACHE BOOL "Disable Thrust header testing" )
+set ( CUB_ENABLE_TESTING OFF CACHE BOOL "Disable CUB tests" )
+set ( CUB_ENABLE_EXAMPLES OFF CACHE BOOL "Disable CUB examples" )
+set ( CUB_ENABLE_HEADER_TESTING OFF CACHE BOOL "Disable CUB header testing" )
+
+# Get it into the current directory.
+FetchContent_MakeAvailable( CCCL )

extern/cccl/README.md

@@ -0,0 +1,4 @@
+# Build Recipe for CCCL
+
+This directory holds a build recipe for building
+[CCCL](https://github.com/NVIDIA/cccl) for this project.