From 6f7f5911fc308971e2af71284cdfe0abd9b41350 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=BCtzel?= <markus.muetzel@gmx.de>
Date: Wed, 28 Feb 2024 23:01:20 +0100
Subject: [PATCH] CMake: Import installed CMake target for KLU from SuiteSparse
 (#407)
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Newer versions of SuiteSparse install import targets for its libraries.
Use the import target of KLU as installed by SuiteSparse if it is
available and the user didn't set flags to select a different one.

This fixes an issue if the SuiteSparse headers are installed at their
new default location `$prefix/include/suitesparse`.

---------

Signed-off-by: Markus Mützel <markus.muetzel@gmx.de>
Co-authored-by: Daniel R. Reynolds <reynolds@smu.edu>
Co-authored-by: Cody Balos <balos1@llnl.gov>
Co-authored-by: David Gardner <gardner48@llnl.gov>
---
 cmake/SUNDIALSConfig.cmake.in   | 10 +++++++---
 cmake/tpl/FindKLU.cmake         | 15 +++++++++++++++
 doc/shared/sundials/Install.rst | 15 +++++++++++++--
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/cmake/SUNDIALSConfig.cmake.in b/cmake/SUNDIALSConfig.cmake.in
index 58bbe448e5..9cbe9e6c23 100644
--- a/cmake/SUNDIALSConfig.cmake.in
+++ b/cmake/SUNDIALSConfig.cmake.in
@@ -91,9 +91,13 @@ if("@ENABLE_HYPRE@" AND NOT TARGET SUNDIALS::HYPRE)
 endif()
 
 if("@ENABLE_KLU@" AND NOT TARGET SUNDIALS::KLU)
-  add_library(SUNDIALS::KLU INTERFACE IMPORTED)
-  target_link_libraries(SUNDIALS::KLU INTERFACE "@KLU_LIBRARIES@")
-  set_target_properties(SUNDIALS::KLU PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "@KLU_INCLUDE_DIR@")
+  if("@KLU_SUITESPARSE_TARGET@")
+    find_dependency(KLU)
+  else()
+    add_library(SUNDIALS::KLU INTERFACE IMPORTED)
+    target_link_libraries(SUNDIALS::KLU INTERFACE "@KLU_LIBRARIES@")
+    set_target_properties(SUNDIALS::KLU PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "@KLU_INCLUDE_DIR@")
+  endif()
 endif()
 
 if("@ENABLE_KOKKOS@" AND NOT TARGET Kokkos::kokkos)
diff --git a/cmake/tpl/FindKLU.cmake b/cmake/tpl/FindKLU.cmake
index cad926d4b8..96b9d7343b 100644
--- a/cmake/tpl/FindKLU.cmake
+++ b/cmake/tpl/FindKLU.cmake
@@ -30,6 +30,21 @@
 #   KLU_LIBRARIES   - all of the libraries needed for KLU
 # ---------------------------------------------------------------
 
+if (NOT (KLU_INCLUDE_DIR OR KLU_LIBRARY_DIR OR KLU_LIBRARY))
+  # Prefer the import target from upstream SuiteSparse if it is available
+  # and the user didn't point to a specific (different) version.
+  find_package(KLU CONFIG)
+
+  if(TARGET SuiteSparse::KLU)
+    if(NOT TARGET SUNDIALS::KLU)
+      add_library(SUNDIALS::KLU ALIAS SuiteSparse::KLU)
+      set(KLU_SUITESPARSE_TARGET ON)
+      mark_as_advanced(KLU_SUITESPARSE_TARGET)
+    endif()
+    return()
+  endif()
+endif()
+
 # Set library prefixes for Windows
 if(WIN32)
   set(CMAKE_FIND_LIBRARY_PREFIXES lib ${CMAKE_FIND_LIBRARY_PREFIXES})
diff --git a/doc/shared/sundials/Install.rst b/doc/shared/sundials/Install.rst
index 6843e2c376..aad89e575d 100644
--- a/doc/shared/sundials/Install.rst
+++ b/doc/shared/sundials/Install.rst
@@ -1336,11 +1336,22 @@ Texas A&M University and is available from the `SuiteSparse GitHub repository
 
 To enable KLU, set ``ENABLE_KLU`` to ``ON``, set ``KLU_INCLUDE_DIR`` to the
 ``include`` path of the KLU installation and set ``KLU_LIBRARY_DIR``
-to the ``lib`` path of the KLU installation.  The CMake configure will
-result in populating the following variables: ``AMD_LIBRARY``,
+to the ``lib`` path of the KLU installation.  In that case, the CMake configure
+will result in populating the following variables: ``AMD_LIBRARY``,
 ``AMD_LIBRARY_DIR``,  ``BTF_LIBRARY``, ``BTF_LIBRARY_DIR``,
 ``COLAMD_LIBRARY``, ``COLAMD_LIBRARY_DIR``, and ``KLU_LIBRARY``.
 
+For SuiteSparse 7.4.0 and newer, the necessary information can also be gathered
+from a CMake import target.  If SuiteSparse is installed in a non-default
+prefix, the path to the CMake Config file can be set using
+``CMAKE_PREFIX_PATH``.  In that case, the CMake configure step won't populate
+the previously mentioned variables.  It is still possible to set
+``KLU_INCLUDE_DIR`` and ``KLU_LIBRARY_DIR`` which take precedence over a
+potentially installed CMake import target file.
+
+In either case, a CMake target ``SUNDIALS::KLU`` will be created if the KLU
+library could be found.  Dependent targets should link to that target.
+
 SUNDIALS has been tested with SuiteSparse version 5.10.1.